Re: IDLE: clearing the screen
On 08/06/2024 20:18, Rob Cliffe via Python-list wrote:
> OK, here is the advanced version:
> import os
> class _cls(object):
> def __repr__(self):
> os.system('cls')
> return ''
> cls = _cls()
>
> Now when you type
> cls
> it clears the screen.
For me on a Mac it clears the terminal screen that I used
to launch IDLE and prints a single blank line on the IDLE
shell. (And I have to use "clear" instead of "cls" of course.
A quick Google suggests that printing Ctrl-L (formfeed?) might
be a platform agnostic solution. But that didn't work for me
in IDLE either. I think this is one where the best bet is to go
into the IDLE code and add a Shell submenu to clear screen!
Apparently it's been on the workstack at idle-dev for a long
time but is considered low priority...
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
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http://www.flickr.com/photos/alangauldphotos
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Re: Terminal Emulator (Posting On Python-List Prohibited)
On 18/05/2024 19:12, Piergiorgio Sartor via Python-list wrote: >> So venvs make managing all that pretty convenient. Dunno why everybody's >> so down on venvs... Not so much down on them, they are just one extra step that's mostly not needed(in my use case) > Only people which are *not* using python... :-) > > In my experience, venvs is the only possible > way to use python properly. Well, I've been using Python since 1998 on Linux, Windows and MacOS and have yet to find a use for a venv. I've played with them when they first came out but haven't actually found a scenario where I've thought "I need a venv for that!" But then I'm a sole user, I have 3 or 4 projects going but only me working on them. I only have 2 Python versions at any time and the OS handles that just fine without any venvs. > The dependency nightmare created by python, pip > and all the rest cannot be resolved otherwise. I've honestly never experienced this "nightmare". I install stuff and it just works. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Terminal Emulator
On 14/05/2024 18:44, Gordinator via Python-list wrote: > I wish to write a terminal emulator in Python. I am a fairly competent > Python user, and I wish to try a new project idea. What references can I > use when writing my terminal emulator? I wish for it to be a true > terminal emulator as well, not just a Tk text widget or something like that. The first thing is to decide which terminal. A VT100 is very different from a 3270. And even a VT330 is quite different from a VT100 although sharing a common subset of control codes. And if you start looking at graphical terminals things get even more interesting! The other thing to consider is whether it will be a standalone app or a GUI component. If the latter do you want to expose your own API or clone the manufacturers? Or both?! Or you could make it an object that can be used both in GUIs and in "robotic" or "batch" mode. So many options. Most of the specs are available online and there must be dozens of terminal emulators around written in C so you should have plenty of sample code to study. Good luck! -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: How to Add ANSI Color to User Response
On 10/04/2024 19:50, WordWeaver Evangelist via Python-list wrote:
> I have a simple question. I use the following textPrompt in some of my Jython
> modules:
> '\n[1;33mYour choice is? (A B C D E): ', maxChars=1, autoAccept=False,
> forceUppercase=True)
> Is there a way to add an ANSI color code to the end
Normally, for any kind of fancy terminal work, I'd say use curses.
But I suspect Jython may not support curses?
On the offchance it does do curses it would look like:
import curses
def main(scr):
if curses.has_colors(): # check the terminal supports color
curses.start_color(). # init the color system
curses.init_pair(1,curses.COLOR_YELLOW,curses.COLOR_BLUE)
# Now start adding text coloring as desired...
scr.addstr(0,0,"This string is yellow and blue",
curses.color_pair(1))
scr.refresh(). # make it visible
else: scr.addstr("Sorry, no colors available")
curses.wrapper(main)
HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
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http://www.flickr.com/photos/alangauldphotos
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Re: xkcd.com/353 ( Flying with Python )
On 30/03/2024 07:04, Greg Ewing via Python-list wrote: > On 30/03/24 7:21 pm, HenHanna wrote: >> https://xkcd.com/1306/ >> what does SIGIL mean? > > I think its' a Perl term, referring to the $/@/# symbols in front of > identifiers. There seem to be several derivation sources including a fantasy world city suspended above a very thin, tall steeple Personally, I know SIGIL as an opensource EPUB editor! None of them seem to have any direct connection to the xkcd cartoon. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Error in Module
On 10/03/2024 18:08, Sanskar Mukeshbhai Joshi via Python-list wrote: > I had made my project in BCA in Python. When I had complete my > project and run the program, at that time I got the error in > runnig my project. The error was ModuleNotFoundError: No module named 'flask'. Flask is a third party package that you need to install separately from Python. It does not come as standard. Have you installed Flask on the computer where you are running your project? If so, how did you download/install it? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Variable scope inside and outside functions - global statement being overridden by assignation unless preceded by reference
On 05/03/2024 22:46, Grant Edwards via Python-list wrote: > Unfortunately (presumably thanks to SEO) the enshittification of > Google has reached the point where searching for info on things like > Python name scope, the first page of links are to worthless sites like > geeksforgeeks. And not just Google, I just tried bing, yahoo and duckduckgo and they are all the same. Not a one listed anything from python.org on the first page... In fact it didn't even appear in the first 100 listings, although wikipedia did manage an entry, eventually. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: RE: Problem resizing a window and button placement
On 27/02/2024 07:13, Steve GS via Python-list wrote: > Aside from using it to resized > the window, is there no way to > know the last value of the > change for use in the program? The last value would be the current width. And you know how to get that as shown in your configure function: Ww = root.winfo_width() > I could write the value to a > label and read it back later That's no different to writing it to global Ww and accessing that as demonstrated in my last code post (with button). >>> It's better just to ask tk > for the values whenever you > need them, as you do inside > your handler. > > How would that be done? Ww = root.winfo_width() Provided you can access the root widget (which is (nearly?) always true) you can get the width of the main window. But can I ask if you have a particular use-case in mind for this? We started out talking about relocating some widgets when the window was resized. We established that the best place to do that was inside the configure event handler, with no need to store the width. (assuming you aren't using a dynamic layout manager(grid/pack/form) which would be better still!) We've now moved on to the more general issue of communicating values between event handlers (although still using the width as our exemplar). Is this just academic interest or do you have a specific need for this? If we know the need we might be able to suggest a specific (and possibly better?)solution. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: RE: RE: Problem resizing a window and button placement
On 26/02/2024 11:02, Steve GS via Python-list wrote:
> Although your code produces the value of Ww outside the function,
> I do not see how I can use the value of Ww unless I close the program.
You have to use a function that operates inside the mainloop.
Thats the nature of event driven programs, all activity happens
inside the mainloop except initialisation and cleanup.
So you need to create an event handler as I described below.
Here is the complete program including the button:
###
import tkinter as tk
Ww=None
def on_configure(*args):
global Ww
Ww = root.winfo_width()
print("Ww Inside = <" + str(Ww) + ">")
def printW(): print("Button Ww = ", Ww)
root = tk.Tk()
bw = tk.Button(root, text="Print Width", command=printW)
bw.pack()
root.bind('', on_configure)
root.mainloop()
print("Ww Outside = <" + str(Ww) + ">")
Notice that the button callback picks up the latest value of Ww.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
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Re: RE: Problem resizing a window and button placement
On 26/02/2024 07:56, Steve GS via Python-list wrote:
> Then there is that discovery
> element: Why is my original
> idea not working? I still
> cannot pass the value back
> from the function. What is
> different about this function
> that others would have given
> me the value?
There is nothing different, see the code below.
print() is a function like any other.
In this case it is called after you close the
window, ie after mainloop() exits.
But any other function called inside
mainloop - eg any other event handler can
also access it.
For example, if you added a button:
def printW(): print("Button Ww = ", Ww)
bw = tk.Button(root, text="Print Width", command=printW)
bw.pack()
You would be able to print the value on demand.
>> import tkinter as tk
>>
>> Ww = None
>>
>> def on_configure(*args):
>> global Ww
>> Ww = root.winfo_width()
>> print("Ww Inside =<"+str(Ww)+">")
>>
>> root = tk.Tk()
>> root.bind('',on_configure)
>> root.mainloop()
>>
>> print("Ww Outside = <"+str(Ww)+">")
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
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Re: RE: Problem resizing a window and button placement
On 25/02/2024 03:58, Steve GS via Python-list wrote:
import tkinter as tk
Ww = None
def on_configure(*args):
global Ww
Ww = root.winfo_width()
print("Ww Inside = <" + str(Ww) + ">")
root = tk.Tk()
root.bind('', on_configure)
root.mainloop()
print("Ww Outside = <" + str(Ww) > + ">")
Produces:
Ww Inside = <200>
Ww Inside = <200>
Ww Inside = <205>
Ww Inside = <205>
Ww Inside = <206>
Ww Inside = <206>
Ww Outside = <206>
HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
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Re: Using my routines as functions AND methods
On 04/01/2024 04:17, Thomas Passin via Python-list wrote:
>> I'm probably missing something obvious here but can't you
>> just assign your function to a class member?
>>
>> def myFunction(obj, ...): ...
>>
>> class MyClass:
>> myMethod = myFunction
>
> That works if you assign the function to a class instance, but not if
> you assign it to a class.
>
> def f1(x):
> print(x)
> f1('The plain function')
>
> class Class1:
> pass
>
> class Class2:
> pass
>
> c1 = Class1()
> c1.newfunc = f1
> c1.newfunc('f1 assigned to instance') # Works as intended
>
> Class2.newfunc = f1
> c2 = Class2()
> c2.newfunc('f1 assigned to class') # Complains about extra argument
Yes but I did the assignment inside the class definition and
that seemed to work just fine:
>>> def g(obj, st): print(st, obj.v)
...
>>> class D:
...def __init__(self,v): self.v = v
...m = g
...
>>> d = D(66)
>>> g(d,'val = ')
val = 66
>>> d.m('v = ')
v = 66
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
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Re: Using my routines as functions AND methods
On 03/01/2024 22:47, Guenther Sohler via Python-list wrote: > Hi, > > In my cpython i have written quite some functions to modify "objects". > and their python syntax is e.g.\ > > translate(obj, vec). e.g whereas obj is ALWAYS first argument. > However, I also want to use these functions as class methods without having > to > write the function , twice. When using the SAME function as a methos, the > args tuple must insert/contain "self" in the first location, so i have > written a function to do that: I'm probably missing something obvious here but can't you just assign your function to a class member? def myFunction(obj, ...): ... class MyClass: myMethod = myFunction Then you can call it as myObject = MyClass() myObject.myMethod() A naive example seems to work but I haven't tried anything complex so there is probably a catch. But sometimes the simple things just work? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Are there any easy-to-use Visual Studio C# WinForms-like GUI designers in the Python world for Tk?
On 29/12/2023 01:05, Félix An via Python-list wrote: > I'm used to C# WinForms, which has an easy-to-use drag-and-drop GUI > designer in Visual Studio. Is there anything similar for Tk? How about > Qt? There are any number of them but few that work well. The best I found was Dabo but it uses its own Framework (based, ISTR, on wxPython?) so not much good for integrating with third party widgets etc. I also used a Python fork of SpecTcl but it died a death I think. The Qt Designer tool works with Python but I never took to Qt as a toolkit although once mastered it is very powerful. Probably the best choice for professional class GUI applications using a GUI builder. And on a Mac the standard Apple XCode GUI builder works fine with Python too, but is Mac specific. > What do you recommend as the easiest way to create GUI programs in > Python, similar to the ease of use of C# WinForms? Provided you aren't getting fancy the basic Tkinter toolset and programming by hand works best for me. Once you get used to it its quick, flexible and fairly easy to debug. I also use wxPython if I need something more sophisticated, but again I just type the code I don't use a GUI builder. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: >>> %matplotlib inline results in SyntaxError: invalid syntax
On 25/12/2023 05:34, geetanajali homes via Python-list wrote: >> import numpy as np >> import pandas as pd >> import random >> import matplotlib.pyplot as plt >> %matplotlib inline >> >> I get an error on the last line. I am running this code in Idle Python >> 3.4.4 Shell... Python names can't start with a % (its the modulo or string formatting operator). I know nothing of the innards of matplotlib so I can only suggest a closer examination of their tutorial information. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Amy known issues with tkinter /ttk on latest MacOS?
On 17/11/2023 03:38, Terry Reedy wrote: > There have been other reports on the cpython issue tracker than Sonoma > broke bits of tk behavior. > https://github.com/python/cpython/issues?q=is%3Aissue+label%3AOS-mac+is%3Aclosed > > shows a couple Thanks Terry, I had a browse and it seems I'm not alone. That's a relief. I'll upgrade to 3.13 when it comes out and hopefully it will go away. (Another suggestion was to use the homebrew python but I don't like having any more homebrew stuff than is absolutely necessary!) Meantime I'll just have to continue nudging the mouse as I click! Alan G. -- https://mail.python.org/mailman/listinfo/python-list
Amy known issues with tkinter /ttk on latest MacOS?
I have a little app that I wrote ages ago (2015) using tkinter/ttk and it just works. Or it did, up until the latest MacOS version upgrade and now it has become very sporadic in response to mouse clicks. For example I have a drop-down list and I can drop the list but then it won't let me select an item. Or sometimes, the selected item is highlighted but the corresponding action doesn't get fired. It is intermittent which makes debugging it difficult. And it's not just lists it also affects regular buttons as well. Right clicks seem to work ok, it's only the left mouse button. Also, I've just noticed that if I move the mouse slightly while clicking that seems to work. There are no error/warning messages in the Console. I'm just wondered if this is a known issue, or just my setup? Any suggestions welcomed. Python version - 3.10.4 OS version - Sonoma 14.1 M1 Mac Mini, 16GB Ram I could upgrade my Python version but I was planning on waiting for the 3.13 release to finalize first. And I doubt if that's the cause anyway. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Newline (NuBe Question)
On 15/11/2023 07:25, Grizzy Adams via Python-list wrote:
> for s in students:
> grades.append(s.school)
> grades.append(s.name)
> grades.append(s.finalGrade())
> if s.finalGrade()>82:
> grades.append("Pass")
> else:
> grades.append("Fail")
> print(grades)
>
> --- End Code Snippit ---
> Do I need to replace "append" with "print", or is there a way to get the
> newline in as I append to list?
Firstly, it is usually a bad idea to mix formatting features(like
newline) with the data. You will need to remove them again if you want
to work with the data itself.
So, better to print the raw data and add the formatting during printing.
There are a couple of options here (well more than a couple actually!)
The simplest is to create another for loop and print each field with a
newline automatically added by print()
Another is to simply join everything in grades together separated by
newlines. Python has a method to do that called join():
print('\n'.join(grades))
Unfortunately it seems your data has a mix of strings and numbers so
that won't work without some tweaks:
print('\n'.join(str(f) for f in grades))
However, I wonder if this really what you want? You have created grades
as a long list containing all of the attributes of all of the students
plus their Pass/Fail status. But you have no (easy)way to access the
Pass/Fail value for each student. Do you really want to store the
Pass/Fail in the student? And then print the students? Like so:
for s in students
if s.finalGrade() > 82:
s.result = "Pass"
else:
s.result = "Fail"
print(s.school)
print(s.name)
...
print(s.result)
Just a thought...
PS. There are neater ways to do this but you may not have covered
those yet so I'll stick to basics.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
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Re: xor operator
On 14/11/2023 00:33, Mats Wichmann via Python-list wrote: > Hardware and software people may have somewhat different views of xor I've come at it from both sides. I started life as a telecomms technician and we learned about xor in the context of switching and relays and xor was a wiring configuration for scenarios where you wanted any single change of switch state to toggle the entire system (think a stairwell with switches on every landing). Later, I got into software engineering and we studied Boolean algebra and xor was an odd number of Truth values, used in parity tests (and in encryption). But from both perspectives xor is pretty clearly defined in how it operates and not, I suspect, what the OP really wants in this case. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Question(s)
On 25/10/2023 12:44, o1bigtenor via Python-list wrote: > Haven't heard of a python IDE - - - doesn't mean that there isn't such - - There are literally dozens with varying degrees of smartness. The big 4 all have Python plugins/environments: Eclipse, Netbeans, VisualStudio, IntelliJ And of course the Apple XCode toolset has a python environment. There are also several Python specific IDEs around too. Most of them are multi-platform: https://www.simplilearn.com/tutorials/python-tutorial/python-ide gives a small sample And of course the old favourites vi/vim and emacs both have comprehensive Python support. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Question(s)
On 25/10/2023 00:08, o1bigtenor via Python-list wrote: > So how does one test software then? Testing is very different to proving! As an industry we do a lot of testing at many different levels. On bigger projects you'll find: - Unit tests - testing small fragments of a bigger program - Integration tests - testing that sub modules of code work together (and code with hardware, if applicable) - System testing - checking that the code(and hardware) as a whole does what it should based on the specs (often done by an independent team) - Performance testing - checking the system runs as fast as it should, using only the memory it should, for as long as it should. - User testing - Can a real user drive it? - security testing - Does it stop the bad guys from messing it up or using it as a gateway? And there are more levels if you are really keen. Testing often(usually!) takes up more time than programming. And there are many, many books written about how to do it. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Question(s)
On 24/10/2023 22:51, Grant Edwards via Python-list wrote: >>> Is there a way to verify that a program is going to do what it is >>> supposed to do even before all the hardware has been assembled and >>> installed and tested? > And the specified customer requirements are usually wrong too. Sure, > the customer said it is supposed to do X, but what they actually > needed was Y. And this is the hardest bit, specifying exactly what you want at a level that can be formally verified. I worked on some safety critical systems a while back(1990s) and we had to formally verify the core (non UI) code. We did this, but it still failed in some scenarios because we verified it against faulty specs which, in turn, were based on the customer's incorrectly stated requirements. Garbage-In-Garbage-Out still applies. Was the 3 months of formal analysis a waste of time? No, we still caught lots of subtle stuff that might have been missed, but it wasn't 100%. The bugs we did have were caught and identified during system tests. So far as I know, nobody has died as a result of any bugs in that system. But, to the OP, the effort in a) Learning the math and gaining experience for formal analysis and b) actually performing such an analysis of real design/code is simply not worth the effort for 99% of the programs you will write. It is much simpler and faster to just test. And test again. And again. Especially if you use automated testing tools which is the norm nowadays. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Why doc call `__init__` as a method rather than function?
On 15/09/2023 11:49, scruel tao via Python-list wrote: > ```python class A: > ... def __init__(self): > ... pass > On many books and even the official documents, it seems that > many authors prefer to call `__init__` as a "method" rather > than a "function". That' because in OOP terminology methods are traditionally implemented as functions defined inside a class (There are other ways to define methods in other languages, but the class/function duology is by far the most common.) What is a method? It is the way that an object handles a message. OOP is all about objects sending messages to each other. Many different objects can receive the same message but they each have their own method of handling that message. (This is called polymorphism.) Over time the most common way to implememt OOP in a language is to invent a "class" structure and to allow functions to either be defined within it or added to it later. In either case these functions are what define how a class (and its object instances) handle a given message. So the function describes the method for that message. And over time that has become shortened to the function inside a class *is* its method. In practice, the message looks like a function call. And the method consists of the function body (and/or any inherited function body). Thus every method is a function (or set of functions) but not every function is a method (or part of one). -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Why do I always get an exception raised in this __init__()?
On 31/08/2023 22:15, Chris Green via Python-list wrote:
> class Gpiopin:
>
> def __init__(self, pin):
> #
> #
> # scan through the GPIO chips to find the line/pin we want
> #
> for c in ['gpiochip0', 'gpiochip1', 'gpiochip2', 'gpiochip3']:
>
> chip = gpiod.Chip(c)
> for l in range(32):
> line = chip.get_line(l)
> if pin in line.name():
> print("Found: ", line.name())
> return
> else:
> raise ValueError("Can't find pin '" + pin + "'")
You don't store the line anywhere.
You need to use self.line
self.line = chip.get_line(l)
if pin...
> def print_name(self):
> print (self.line.name())
>
> def set(self):
> self.line.set_value(1)
>
> def clear(self):
> self.line.set_value(0)
As you do here.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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Re: Multiple inheritance and a broken super() chain
On 05/07/2023 01:27, Chris Angelico via Python-list wrote: >> So I'm curious about how big this "big problem with MI" is in > > Who said it's a big problem with MI? I think it's a very common perception, particularly with newer programmers who have never used it in anger. Any time anyone discusses MI it seems somebody will jump in and warn about diamonds etc. As a result many steer clear of MI, which is a shame. My personal experience of MI is that used appropriately it is a powerful and useful tool. But it must be used in a true is-a type relationship and not just as a kind of cheap reuse mechanism - that's when problems start. Also, mixin style MI is particularly powerful but the protocol between mixin and "subclass" needs to be carefully designed and documented. Like any powerful tool you need to understand the costs of use as well as the potential benefits. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Multiple inheritance and a broken super() chain
On 03/07/2023 19:39, Chris Angelico via Python-list wrote: > On Tue, 4 Jul 2023 at 03:39, Peter Slížik via Python-list >> The legacy code I'm working with uses a classic diamond inheritance. > What happens when Top is initialized twice? This seems like a problem > waiting to happen, and when you moved to using super(), you more than > likely simplified things and fixed things. Slightly off topic but I wonder how many real world problems people have experienced having the top of a diamond initialized twice? The reason I ask is that I ran a maintenance team for about 5 years (early 1990s) working on various OOP projects using MI; in Lisp Flavors, C++(*) and a homebrew variant of C that supported MI. In that time I don't recall ever having problems with top objects being initialized twice (apart from redundant execution of code of course). In most cases the top object was so abstract that its init()/constructor was only doing generic type stuff or opening database sessions/networks etc which got lost and tidied up by garbage collectors. So I'm curious about how big this "big problem with MI" is in practice. I'm sure there are scenarios where it has bitten folks but it never (or very rarely) occurred in our projects. (Of course, being maintenance programmers, the problems may have been ironed out before the code ever reached us! But that wasn't usually the case...) (*) C++ is the odd one out because it doesn't have GC, but then neither does it have an Object superclass so very often MI in C++ does not involve creating diamonds! And especially if the MI style is mixin based. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Fwd: AUTO EDITOR DIDN'T WORK
On 15/06/2023 08:58, Real Live FootBall Tv via Python-list wrote: > I have followed the instructions given on how to install the app. What I > needed was an application to cut of silence from my video and I saw auto > editor demonstrated as one of the applications that could do that. It does > cut the silent areas of an MP4 format video for instance but would save it > as a XML file which in turn would be exported to the video editor that > supports the output from the auto editor app. The one who demonstrated it > in a video used Davinci Resolve to import the XML file, I followed same > process but I couldn't get same result. It looks like you have three parts to this puzzle: - auto-editor - resolve - Python It's not clear which part isn't working but you can at least test Python is working after you install it by running the interpreter in a console/terminal window by typing python at the command prompt. If you get the Python prompt: >>> Then Python is installed OK. After that it's back into auto-editor and resolve and this is not the best place to get answers for those. Resolve at least has an active support forum, so I'd start there(assuming python works!) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Fwd: AUTO EDITOR DIDN'T WORK
Forwarding to list Okay thanks. Meanwhile, I am not tech savvy so I may not say much here. I followed all the commands as given on the website to install auto editor standing it on python but after rendering the XML file, I couldn't open it with my Davinci Resolve 18. I uninstalled and reinstalled about twice and still no success hence I uninstalled it. On Mon, 12 Jun 2023, 23:33 Alan Gauld via Python-list, mailto:python-list@python.org>> wrote: On 12/06/2023 10:26, Real Live FootBall Tv via Python-list wrote: > I did it because I was going to use it with another application, A VIDEO > EDITING APP, Auto EDITOR but it didn't work for some reasons unknown to me. You need to define "didn't work" Did it work as a python interpreter? ie. Did you get a >>> prompt in a terminal? and without involvement from your video editor? If so, what did you do to link it to the video editor? And what was the result? Or did Python not even start? How did you try to use it? What OS are you on? Did the installer run OK? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ <http://www.alan-g.me.uk/> http://www.amazon.com/author/alan_gauld <http://www.amazon.com/author/alan_gauld> Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos <http://www.flickr.com/photos/alangauldphotos> -- https://mail.python.org/mailman/listinfo/python-list <https://mail.python.org/mailman/listinfo/python-list> -- https://mail.python.org/mailman/listinfo/python-list
Fwd: Re: AUTO EDITOR DIDN'T WORK
On 12/06/2023 10:26, Real Live FootBall Tv via Python-list wrote: > I did it because I was going to use it with another application, A VIDEO > EDITING APP, Auto EDITOR but it didn't work for some reasons unknown to me. You need to define "didn't work" Did it work as a python interpreter? ie. Did you get a >>> prompt in a terminal? and without involvement from your video editor? If so, what did you do to link it to the video editor? And what was the result? Or did Python not even start? How did you try to use it? What OS are you on? Did the installer run OK? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Question again
On 16/09/2021 06:50, af kh wrote:
> Hello,
> I was doing some coding on a website called replit
I have no idea what that is but...
> after answering 'no' or 'yes' after the last sentence I wrote,
> the Python window shut off,
That's what you told it to do in the code.
Regardless of which answer the user gives the program
reaches the end and stops.
> in replit I added one more sentence, but it isn't shown on Python,
I dn;t know what this means.
> #Gives greetings to the user
> import random
...
> #Ask to pick between numbers 1~10 to see if you will get lucky today: Third
> question
> number = input("Please pick between numbers 1~10 to see your luck for today:
> ")
>
> #From number 1~3 and an answer
> if number == "1" or number == "2" or number == "3" :
> print("You're in grat luck today!")
>
> #From number 4~7 and an answer
> elif number == "4" or number == "5" or number == "6" :
> print("damn, bad luck is coming your way")
The cde and comment are not consistent.
> #From number 8~10 and an answer
> elif number == "7" or number == "8" or number == "9" or number == "10" :
> print("I cannot sense any luck today, try again next time")
Same here.
> #Add a statement and question: Fourth question
> print("That will be all for today's chitchat, woohooo! would you like to exit
> the chat?")
> #User says 'yes'
> reply = input()
>
> #If user says 'yes' reply 'wait hold on! are you really leaving??': Fifth
> question
> if reply == "yes" :
> print("Wait hold on! are you really leaving??")
>
> #User answers
> answer = input()
> #If user says 'yes' again, reply 'fine! bye then!'
> if answer == "yes" :
> print("Fine! bye then!")
Shouldn't those lines be indented as part of the if statement above?
> #Other than that if user says 'no', reply 'just kidding we're done here haha'
> elif answer == "no" :
> print("just kidding we're done here haha")
But the code always gets to the end, there is nothing
to stop it exiting.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
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Re: Friday Finking: Contorted loops
On 12/09/2021 09:11, jak wrote:
> if the only way to terminate a 'while True' loop is by using the 'break'
> statement, why is it allowed to add the 'else' statement which will only
> contain dead code?
>
> while True:
> break
> else:
> print('dead code')
>
Because to the interpreter the condition is not part of the
language. It is syntactically correct.
An optimiser OTOH might welkl determine that the condition
will never fail and therefore the else clause never be reached,
in which case it would remove the dead code (possibly emitting
a warning in the process?).
A linter likewise might identify the redundant code.
I don't use any python linters, does anyone know if they do
detect such dead spots?
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
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Re: Friday Finking: Contorted loops
On 11/09/2021 15:41, Peter J. Holzer wrote:
> How is C's do/while loop more horrible than Pascal's repeat/until?
Because it is very hard to spot or distinguish from a normal
while loop.
while condition ;
Is a valid (and fairly common) loop in C
so code that has
do{
code
}
while condition;
Looks, for non-trivial cases, like a lot of code followed
by an empty while loop.
The do is easy to miss and the while loop disguised as
a repeat termination is confusing.
repeat
code
until condition
Is far clearer to comprehend since there is no ambiguity.
> In an old collection of small C programs of mine I find:
>
> 35 regular for loops
> 28 while loops
> 2 infinite for loops
> 1 "infinite" for loop (i.e. it exits somewhere in the middle)
> 0 do/while loops.
That wouldn't surprise me, I've only used do/while in C
a handful of times. But in Pascal I use it regularly.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
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Re: Friday Finking: Contorted loops
On 10/09/2021 19:49, Stefan Ram wrote: > Alan Gauld writes: >> OK, That's a useful perspective that is at least consistent. >> Unfortunately it's not how beginners perceive it > ... > > Beginners perceive it the way it is explained to them by > their teacher. I'm not sure that's true. Most beginners, in my experience, learn the syntax from their teachers and then go off and play. What they observe happening is what sticks. And python loop 'else' constructs appear inconsistent to them. As teachers we like to think we are passing on our wisdom to our students but in reality everyone learns from their own experience. The teachers advice is just the starting point. Hopefully, that starting point sends them in the right direction but that's the best we can hope for. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Friday Finking: Contorted loops
On 10/09/2021 16:36, MRAB wrote: >> while...else... >> >> executes the else if the body of the loop does NOT get executed. >> >> for...else... >> >> executes the else iff ALL iterations of the for loop DO complete. >> > [snip] > > In both cases, it executes the 'else' part if it didn't break out of the > loop. That's it. OK, That's a useful perspective that is at least consistent. Unfortunately it's not how beginners perceive it and it causes regular confusion about how/when they should use else with a loop. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Friday Finking: Contorted loops
On 10/09/2021 00:47, Terry Reedy wrote: > even one loop is guaranteed.) "do-while" or "repeat-until is even rarer > since fractional-loop include this as a special case. Is there any empirical evidence to support this? Or is it just a case of using the tools that are available? In my experience of using Pascal (and much later with Delphi) that I used repeat loops at least as often as while loops, possibly more. But using Python and to a lesser extent C (which has a rather horrible do/while) construct I use while loops (often with an if-break) simply because that's what the language offers. So is it the case that the "need" for repeat loops is rare, simply a result of there being no native repeat loop available? After all we could have done without a for loop too and just used a while loop for everything (as was done in Oberon(?) ) Would we then state that the use of for loops was rare? But I would hope that any empirical research would look at the wider function of the loop and its purpose rather than merely analyzing the syntax and keywords. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Friday Finking: Contorted loops
On 09/09/2021 22:36, dn via Python-list wrote: > Even in fairly modest Python constructs, we quickly repeal the one-in, > one-out philosophy because try...except operates by providing another > exit-path. Exceptions are exceptional by their nature (or should be!) As such they can arguably be excused from the SP strictures. But python complicates this tenet still further by adding an else clause to its loops. And complicating this still more is that these else clauses have almost exactly opposite effects. while...else... executes the else if the body of the loop does NOT get executed. for...else... executes the else iff ALL iterations of the for loop DO complete. This confuses beginners immensely - and quite a few non beginners too; which is probably why they are not often seen "in the wild". This adds to the question of where exactly does a Python loop end? Is it after the code-suite following the loop construct? Or is it after the else code-suite, where such exists? Returning to the specific case of a repeat structure. In the case of a while loop the else offers another option: while condition loop-body else loop-body Now loop-body always gets executed at least once. But at the cost of duplicating the loop-body code, thus violating DRY. Just another thought... -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: on writing a while loop for rolling two dice
On 07/09/2021 15:53, Grant Edwards wrote:
> I remember engineering manager I worked with about 35 years ago who
> used a set of C macros to try to make his code look as much like BASIC
> as possible:
>
> #define IF if (
> #define THEN ) {
> #define ELSE } else {
> #define ENDIF }
> ...
>
> IIRC he copied them out of a magazine article.
That was quite common in C before it became popular(early/mid 80s).
I've seen Pascal, Algol and Coral macro sets in use.
You could even download pre-written ones from various
bulletin boards (remember them?!) for a while.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
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http://www.flickr.com/photos/alangauldphotos
--
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Re: The sqlite3 timestamp conversion between unixepoch and localtime can't be done according to the timezone setting on the machine automatically.
On 03/09/2021 18:37, Chris Angelico wrote: Without DST the schools opened in the dark so all the kids had to travel to school in the dark and the number of traffic accidents while crossing roads jumped. > > Are you saying that you had DST in winter, or that, when summer *and* > DST came into effect, there was more light at dawn? Because a *lot* of > people confuse summer and DST, and credit DST with the natural effects > of the season change. OK, I see the confusion. What I should point out was that the experiment involved us staying on DST and not reverting to UTC in the winter - that unified us with most of the EU apparently... So although I'm saying DST it was really the non-reversion from DST to UTC that caused problems. Arguably, if we just stayed on UTC and didn't have DST at all there would be no issue - except we'd be an hour out of sync with the EU. (Post Brexit that may not be seen as a problem!! :-) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: The sqlite3 timestamp conversion between unixepoch and localtime can't be done according to the timezone setting on the machine automatically.
On 02/09/2021 19:30, Chris Angelico wrote: >> Without DST the schools opened in the dark so all the kids >> had to travel to school in the dark and the number of >> traffic accidents while crossing roads jumped. > > How do they manage in winter? That was the winter. Sunrise wasn't till 10:00 or so and the schools open at 9. With DST sunrise became 9:00 and with pre-dawn light it is enough to see by. Its a recurring theme. Every now and then some smart young politician from the south of the UK suggests doing away with DST and a large crowd of northerners jump up and say no way! > Can that be solved with better street> lighting? They had street lighting but it casts dark shadows etc. In fact modern LED based street lighting is worse in that respect that the old yellow sodium lights were. But where it doesn't exist the cost of installing street lighting in small villages is too high compared to just changing the clocks. And of course street lighting has a real running cost that would be reflected in the local council taxes, and nobody wants to pay more of them! After all street lighting has been available for over 150 years, if they haven't installed it by now (I mean, nearly everywhere has some lighting, at least on the main roads, it's just the smaller back streets that tend to be dark.) > That was fifty years ago now, and the negative consequences > of DST are far stronger now. But not apparent to most people. Most still see it as a benefit because they get longer working daylight. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: The sqlite3 timestamp conversion between unixepoch and localtime can't be done according to the timezone setting on the machine automatically.
On 02/09/2021 20:11, MRAB wrote: >> In one of them (I can't recall which is which) they change on the 4th >> weekend of October/March in the other they change on the last weekend. >> >> > In the EU (and UK) it's the last Sunday in March/October. > > In the US it's second Sunday in March and the first Sunday in November. > > I know which one I find easier to remember! Interesting. I remember it as closer than that. The bugs we found were due to differences in the DST settings of the BIOS in the PCs. (They were deliberately all sourced from DELL but the EU PCs had a slightly different BIOS). The differences you cite should have thrown up issues every year. I must see if I can find my old log books... -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: The sqlite3 timestamp conversion between unixepoch and localtime can't be done according to the timezone setting on the machine automatically.
On 02/09/2021 19:28, Chris Angelico wrote: >> Except for the places that don't follow the IANA scheme and/or >> dynamically change their time settings on a whim. To be complete >> you need the ability to manually override too. >> > > What places are those? Mainly small non-tech oriented places such as small pacific islands or principalities with local governance - such as by a group of tribal elders. I mentioned earlier the example of Andorra announcing on the Friday night before a DST change that they were deferring it for a week to preserve the skiing conditions. But we came across several similar situations in dealing with multi-national service centres. > IANA maintains the database by noticing changes > and announcements, and updating the database. But don;t those have to be electronic in nature? How, for example would it pick up the radio news announcement mentioned above? > governments need to "opt in" or anything. Stuff happens because people > do stuff, and people do stuff because they want to be able to depend > on timezone conversions. Umm, they do DST because it makes their lives easier - more daylight, extra work time. etc. The needs of, or impact on, computers in these kinds of small localities and communities are way down the pecking order. > There ARE times when a government makes a change too quickly to get > updates out to everyone, especially those who depend on an OS-provided > copy of tzdata, so I agree with the "on a whim" part. Though, > fortunately, that's rare. I agree it is very rare and if you only operate in mainstream localities you probably never see it as an issue, it's only when you need to support "off grid" locations that manual control becomes important. Also the problems we had were about 15 years ago, things may be better ordered nowadays. (I've been retired for 7 years so can't speak of more recent events) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: The sqlite3 timestamp conversion between unixepoch and localtime can't be done according to the timezone setting on the machine automatically.
On 31/08/2021 23:31, Chris Angelico wrote:
> Ah, good to know. I think that actually makes a lot of sense; in the
> US, they try to let everyone pretend that the rest of the world
> doesn't exist ("we always change at 2AM"), but in Europe, they try to
> synchronize for the convenience of commerce ("everyone changes at 1AM
> UTC").
There's another gotcha with DST changes. The EU and USA have different
dates on which they change to DST.
In one of them (I can't recall which is which) they change on the 4th
weekend of October/March in the other they change on the last weekend.
That means on some years (when there are 5 weekends) there is a
week when one has changed and the other hasn't. That caused us
a lot of head scratching the first time we encountered it because
our service centres in the US and EU were getting inconsistent
time reporting and some updates showing as having happened in
the future!
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
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Re: The sqlite3 timestamp conversion between unixepoch and localtime can't be done according to the timezone setting on the machine automatically.
On 31/08/2021 22:32, Chris Angelico wrote: > If we could abolish DST world-wide, life would be far easier. All the > rest of it would be easy enough to handle. We tried that in the UK for 2 years back in the '70s and very quickly reverted to DST when they realized that the number of fatalities among young children going to school doubled during those two years. Without DST the schools opened in the dark so all the kids had to travel to school in the dark and the number of traffic accidents while crossing roads jumped. In fact during WW2 they increased DST to 2 hours (that was for the farmers!) because it meant that farm labourers would start work at first light, effectively extending the working day. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: The sqlite3 timestamp conversion between unixepoch and localtime can't be done according to the timezone setting on the machine automatically.
On 31/08/2021 22:13, Chris Angelico wrote: > But ultimately, it all just means that timezones are too hard for > humans to handle, and we MUST handle them using IANA's database. It is > the only way. Except for the places that don't follow the IANA scheme and/or dynamically change their time settings on a whim. To be complete you need the ability to manually override too. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: The sqlite3 timestamp conversion between unixepoch and localtime can't be done according to the timezone setting on the machine automatically.
On 31/08/2021 13:45, Chris Angelico wrote: > (I find the Ireland situation particularly amusing. Time zones and daylight saving arrangements in particular are a nightmare at the micro level. I once worked on a large customer support application which required all dates/times to be viewable in UTC plus any of: - The local support centre's time (eg. Tokyo, Japan) - The customer organization's local time(eg. Seoul, Korea) - The local site time (some remote island in the pacific...) The big problem was the last one since some small countries have local arrangements for timezones that don't conform to the official ones. One pacific island had dual "patrons" and to avoid offending either they adopted a non-standard "timezone" half-way between the two patron's zones! In another case we had the principality of Andorra deciding to put off switching to DST for an extra week because it would make the snow melt faster and spoil the skiing! This was decided by the council on the Friday before it was due to happen and announced on the local radio... I got more grey hairs on that project than any other. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Python UI (was Re: urgent)
On 29/08/2021 11:28, Hari wrote: > i was download ur python software but it is like boring user interface I agree it is a boring user interface. Just 3 chevrons: >>> You can change it a little if you want but ultimately its just an invitation to type commands. What kind of interface did you have in mind? If you want a GUI to develop code there are literally dozens of those. But ultimately programming is about typing text into an editor. > me like young student to learn ,can u have any updates? There are many tools to help you work with python. If you tell us what kind of things you want we can tell you where to find them (if they exist!) But the basic Python interpreter is primarily there to run your programs, it's hard to see how you can make that less boring without also making it very inefficient. And professional users would hate that! -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: on writing a while loop for rolling two dice
On 28/08/2021 21:50, Hope Rouselle wrote: >>> roll_count = 0 >>> while True: >>> outcome = roll_two_dice() >>> roll_count += 1 >>> if outcome[ 0 ]== outcome[ 1 ]: break >>> return roll_count, outcome[ 0 ] >> > > Wait, I'm surprised ``outcome'' is still a valid name at the > return-statement. Wasn't it defined inside the while? If that really bugs you just replace the break with the return. >>> if outcome[ 0 ]== outcome[ 1 ]: >>>return roll_count, outcome[ 0 ] Now its all inside the loop. But remember readable code is better than cute code every time. And personally I'd just declare the x,y up front. Easier to understand and debug IMHO. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: tkinter
On 21/08/2021 19:37, Tony Genter wrote: >Tkinter stopped working overnight from 8/20/2021 to 8/21/2021. Last night >I was working on tutorials to work on a GUI and this morning every file >that uses tkinter is broken stating that no module `tkinter' exists. Are you sure you were running Python v3 and not python v2? In v2 tkinter is spelled Tkinter. If that is the issue then reinstalling python v3.x and ensuring that it is the executable used should resolve the issue. Another option might be that you are using virtual environments which could result in all manner of chaos and confusion if you inadvertently start the wrong one... -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Tkinter widgets for desktop database application
On 13/07/2021 21:24, Rich Shepard wrote: > What have other developers used for the UI on a stand-alone database > application not using a web browser? Mostly I just use a scrolledlistbox and a set of functions for formatting the data into columns for display. The big snag is you can't do spreadsheet-like things such as select a single field value or sort by a single column without writing a fair bit of code. But for simple display, and selection of a single record it works ok. But a good grid control would be nice. I did try to use the Tix.grid widget but failed. And now Tix is deprecated. I'm sure there must be a third-party one somewhere but I've never taken the time to hunt one down. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: tkinter: tksheet
On 17/06/2021 00:15, Rich Shepard wrote: > When I view my contacts table it needs to includes attributes from the > company, people, and contacts tables so I can view all prior contacts with > that person. Sounds like a job for a database view. Can you modify the database schema? Could you create a view - even a temporary one just while your app is running? Alternatively, and I've done this trick myself, create an in-memory SqlLite database with a table that holds all the columns you want then fetch the data from the master and manipulate/view it from Sqlite - this makes sorting by different columns fast and simple. The downside is you have to refresh it periodically or you will miss all changes in the master. > Many years ago I used wxPython. For several reasons I decided to learn and > use tkinter from now one. One reason is that the application for my clients > will run mostly on windows hosts and I want to limit the software they need > to install and maintain in order to run it. Sure, that's the main reason I use tkinter too. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: tkinter: tksheet
On 16/06/2021 21:45, Rich Shepard wrote: > The two applications I'm building are both database applications. If > tksheet() is not the most appropriate widget to display database tables what > alternative would be better? I've not used tksheet but it sounds like it might be worth investigating. There is a grid in Tix but its quite hard to use and Tix is now deprecated. It was also a bit unreliable when used from Python (that's euphemistic for "I couldn't get it to work!" :-) But there is nothing I know of for Tkinter that provides views of database tables in the way that Delphi or VB or C# do, for example. You have to extract the data using SQL and populate the table and manage all changes (of both view and data) yourself. A good grid component would be a huge boon for tkinter, its one of the most commonly used widgets in VB/Delphi etc A DB-API linked grid would be the height of luxury... If you do a lot of that kind of desktop apps then you could look at Dabo which is built on wxPython but has links to databases. Unfortunately it looks like work ground to a halt about 5 years ago. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Terminology: EU language skills, and Master to Main (or ...)
On 13/06/2021 04:21, dn via Python-list wrote: > What do you think a professionally-recognisable series of skill-levels > for programmers? This has been done or attempted many times, with perhaps the most complete scheme being the British Computer Society's "Industry Standard Model" which breaks jobs/skills in the industry into many categories(30 or so?) and within each category there are up to 6 levels of achievement. (Some skills don't have the lowest levels(e.g. architect) while some only have lower levels. The theory being a level 6 practitioner in and skill is equally "good" as a level 6 in any other skill. One of the skills is programming, and significantly, it is language independent. I don't know if the ISM is still in use, it is many years since I worked with the BCS as the training officer for our office. But there used to be a comprehensive set of web pages describing the requirements for each level for each skill. A quick search for BCS ISM didn't throw up a link, sorry. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Tkinter8.6: date picker
On 11/06/2021 22:20, Rich Shepard wrote: > I need a date picker +1 -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: fabric: fab command
On 02/06/2021 14:35, jayshankar nair via Python-list wrote: > import tools.fab.dev_utils as dev_utilsImportError: No module named > tools.fab.dev_utils > Please let me know which package i have to install. Work backwards. Can you import tools.fab? Can you import tools? Once you know what you do have you can figure out what you don't and why. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Neither pdb or print() displays the bug
On 01/06/2021 21:18, Rich Shepard wrote:
> On Sun, 30 May 2021, Cameron Simpson wrote:
>
>> I've only just started with pdb. As of Python 3.7 there's a builtin
>> function named breakpoint() which drops you into the debugger.
> I'm stuck with neither approach (pdb, print()) working.
> The activitytypes.py module:
>
> class ATMainWindow(qtw.QMainWindow):
>
> def __init__(self):
> super().__init__()
>
> # Model/View here.
> self.model = qts.QSqlTableModel(db=db) # for single table
> self.model.setTable('activitytypes')
> self.model.select()
>
> self.table = qtw.QTableView()
> self.table.setModel(self.model)
>
> self.setFixedSize(qtc.QSize(800, 600))
Assuming this is the line you want to examine set a beakpoint just above
it using the function that Cameron mentioned
(Or just set a breakpoint on the init() from pdb...
Trying to use step/next to debug an event driven application
is next to impossible. set breakpoints on the methods that
get triggered by events then generate the event to reach
the breakpoint.
Or, as in this case, on the init if you want to examine
objects as they are created.
As a general rule if you have to hit next/step more
than half a dozen times in a row you are probably making
extra work for yourself!
>> $/development/business_tracker/activitytypes.py(29)()
> -> window = ATMainWindow()
> (Pdb) n
> False
>> $/development/business_tracker/activitytypes.py(30)()
> -> window.show()
> (Pdb) n
>> $/development/business_tracker/activitytypes.py(32)()
> -> app.exec_()
> (Pdb) n
> n
>> $/development/business_tracker/activitytypes.py(32)()->None
> -> app.exec_()
> (Pdb) n
I'm not sure why you got that twice.
I'd expect you to only see it once.
>
> and there it sits. No (Pdb) prompt, nothing. And no printed statements.
It's waiting while the app runs and for you to terminate it.
> I'd appreciate recommendations on the process to find where the bug lives
> since I can't seem to find it with print() or line-by-line in pdb.
Use breakpoints, don't try to step through the code from the
beginning - there lies madness!
And for event handlers that get called a lot use conditional
breakpoints so that you only stop when you want to.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
https://mail.python.org/mailman/listinfo/python-list
Re: Definition of "property"
On 31/05/2021 15:59, Dennis Lee Bieber wrote: > On Sun, 30 May 2021 21:20:24 +0100, Alan Gauld via Python-list > declaimed the following: > >> On 30/05/2021 17:57, Irv Kalb wrote: >>> I am doing some writing (for an upcoming book on OOP), and I'm a little >>> stuck. >> >> Oh dear, that's one of myt hot buttons I'm afraid! >> I hope it really is about OOP and not about classes. Classes >> are such a minor part of OOP that it is depressing how many > To me, OOP tends to be language specific... OOP is supposed to be a programming paradigm in the same way that Functional or Logic programming are paradigms. Its all about how you organise your code. It should be based on message passing between autonomous agents(objects). Classes etc are language constructs aimed at making OOP easier, but they are not OOP. It's very easy to build a class/object based program that is not in any way OOP (in fact I'd go as far as to say the majority of such programs today come into that category). It's also possible (but difficult!) to build an OOP program without classes. Incidentally, I'm not arguing that classes should not be used in imperative programming, they can be very powerful there too. Just that using classes is not necessarily OOP. > Finding books on OOAD -- which should be language agnostic -- is > more difficult, and tend to turn into books about how to use > UML rather than how to analyze/design using OO. That's a fairly modern phenomenon. Most of the early books about OOAD were language agnostic - even when they used a language for demonstration purposes. Books like Grady Booch's classic OOAD, or Peter Coad's series with Ed Yourdon. The so-called method wars. They all had their own methodology, but mostly that was just diagrammatic variances. The underlying techniques and resultant structures were the same. (And hence the move to UML, which is just a notation - an extremely useful one, although often abused through over zealous application.) Even Rumbaugh's OMT book was meant to be general OOD, although IMHO it was the least OO of all of them being heavily based on data modelling. Sadly, there are very few books today that even attempt to describe the difference between OOP and the more common procedural programming paradigm. Discussions of OOP have degenerated into discussions about OOPL features rather than how to build worlds of objects passing messages to each other. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: How to debug python + curses? [was: RE: Applying winpdb_reborn]
On 31/05/2021 16:16, Grant Edwards wrote: > On 2021-05-30, Alan Gauld via Python-list wrote: >> You are not alone. debugging curses is one of the biggest obstacles to >> its use. > > Can't you just run the debugger in a different window and attach to > the process you want to debug? That's how one uses a debugger with > curses apps written in C/C++. That's how we did it when I used curses on VMS/Unix using C. But I confess I didn't think you could attach any python debugger to another python session? > Or I add debugging printf calls which > write to stderr and redirect stderr to a file. I do use logging sometimes but its not as immediate as seeing the messages in the application as you run it. >> My approach is to define a status line at the bottom of my program and >> write print statements into that window. Something like: > > Why not just use the standard python logging facility and log to a > file or another terminal window? I find the immediacy of an in-window message much easier. Its like using print() statements in a regular CLI application. Its there in front of you, no other terminals to look at. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Definition of "property"
On 31/05/2021 01:24, Greg Ewing wrote: > On 31/05/21 8:20 am, Alan Gauld wrote: >> >> That's a very Pythonic description. > > If it's a book about Python, it needs to be. The word "property" > has a very specialised meaning in Python. > > In some other languages it's used the way we use "attribute" in > Python. So a Python-specific definition is necessarily going > to be very different from a generic one. That was the point, the OP said it was a book about OOP. Not a book about "OOP in Python". The two are not synonymous. If we go back to the very beginnings of OOP, properties were defined as the publicly available state variables of the object. (Some others favoured using "properties" to describe the entire set of messages to which an object could respond). In classification theory they are defined as "the essential characteristics of an object that identify it with a class" Some theorists also insist that such properties be immutable after instantiation of the object. The first could be considered quite close to what Python does(or allows you to do) but the second is quite different! Although properties can be used to create a form of immutablity. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Definition of "property"
On 30/05/2021 23:57, Mike Dewhirst wrote: > > A property is an object method masquerading as a cachable object attribute Or a group of methods perhaps? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: How to debug python + curses? [was: RE: Applying winpdb_reborn]
On 30/05/2021 18:26, pjfarl...@earthlink.net wrote: > I tried winpdb-reborn some time last year on my Win10 system (python 3.8.3 > at that time), but could not figure out how to use it to debug a python > script that uses the curses module. You are not alone. debugging curses is one of the biggest obstacles to its use. My approach is to define a status line at the bottom of my program and write print statements into that window. Something like: def main(stdwin): appwin = curses.newwin(...) # LINES-1 high status = curses.newwin(...) # 1 line high positioned on bottom # more code here status.addstr(0,0, "Value of foo = %s" % foo) curses.wrapper(main) After debugging the status window can either be retained as an application status bar or removed and the main window enlarged by one line... If anyone else has found a better way to debug curses code I'm also keen to hear! HTH -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Definition of "property"
On 30/05/2021 17:57, Irv Kalb wrote: > I am doing some writing (for an upcoming book on OOP), and I'm a little > stuck. Oh dear, that's one of myt hot buttons I'm afraid! I hope it really is about OOP and not about classes. Classes are such a minor part of OOP that it is depressing how many books and articles focus on them to the exclusion of all else that make up the OOP paradigm! Anyway, rant over... > I understand what a "property" is, how it is used and the benefits, Do you? What is that based on? Is it how properties are used in OOP? Or how they are used in Python? Is your book truly about OOP or how Python does OOP (very different things!) How do python properties compare to properties in other languages like Object Pascal(aka Delphi) and Eiffel for example? Which of these 3 options most closely models the pure OOP concept of a property? > definition of property. In OOP or in Python? Or both? > A property object has getter, setter, and deleter methods > usable as decorators that create a copy of the property > with the corresponding accessor function set to the decorated function. That's a very Pythonic description. > (I would like to avoid going through the whole derivation > with the property function, as that would distract from > the points that I am trying to make.) Which are? Hopefully, about abstraction of data and function/methods therby encouraging polymorphic representations of program structures, which is the essence of OOP. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Python doesn't work
On 30/05/2021 12:23, Mr.Incognito wrote: >Hello > >I downloaded the latest versioon of Python and tried to open several .py >files, but it doesn't open. It opens for a sec, then closes itself. I >tried uninstalling and reinstalling, but it doesn't work. Most likely it is working but faster than you can see. Python is a program interpreter so if you simply execute a .py file, the interpreter will execute it and terminate. Any output will be displayed in a terminal window which will close when the interpreter finishes. The way round that is to launch the programs from inside an existing command shell. assuming you are on Windows hit Windows-R and type cmd to get a Windows> prompt. Then type C:\WINDOWS> py \path\to\python\file.py And you should see the program output. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Applying winpdb_reborn
On 30/05/2021 00:03, Cameron Simpson wrote: > I'd imagine debugging is much like it is in C. Wait for the breakpoint > to trip, then inspect the programme variables. That's a pretty crude form of debugging (although much better than just single stepping from the beginning!). Adding conditional breakpoints that stop only when variables are at certain values, tracepoints that print out a set of values every time a line is executed and watchpoints that keep a running display of a set of variables all allow much faster location of errors. I don't recall how many of those pdb supports but I'm pretty sure watch points and conditional breaks are there. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Applying winpdb_reborn
On 29/05/2021 19:10, Dennis Lee Bieber wrote: > On Sat, 29 May 2021 09:51:04 -0700 (PDT), Rich Shepard > declaimed the following: >> What I find interesting is that every web page I find on 'using pdb' does no >> more than explain the available commands; they don't explain the debugging >> process. That's like showing someone what the word processor menus do; it >> doesn't teach the user how to be a writer. I would point out that my book on learning to program included a chapter on using debugging, half of which was on pdb and how to use it. But that book is now over 20 years old and based on Python 1.5.3! but interestingly nearly all the reviewers specifically praised my inclusion of a chapter on debugging. >> I knew the debugging process with Fortran and C, but haven't learned how to >> effectively use pdb to find bugs that don't issue a traceback or obvious >> wrong answer such as my module displaying an empty window with no widgets. Like most debuggers, set breakpoints, watchpoints and variable traces. > The only debugger I used to be familiar with was that of (Open)VMS. My first job after graduating was writing white-box test scripts for a PABX control system. It was done by writing VMS Debug scripts and then running those scripts with various input files to provide the different initialization settings. I wrote around 100K lines of debug scripts to test around 60K lines of C. It was an amazingly powerful debugger. > I don't even want to think of GDB... I used gdb a few years after VMS DBG and thought it a dreadfully primitive beast by comparison. The scripting and automation features in particular were arcane by comparison. But they are all more similar to pdb than to winpdb. Maybe the OP could consider IDLE, it would at least be closer to an IDE debugger than pdb! And in its latest incarnations Idle is becoming a fairly useful tool once more. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: string storage [was: Re: imaplib: is this really so unwieldy?]
On 26/05/2021 22:15, Tim Chase wrote: > If you don't decode it upon reading it in, it should still be 100MB > because it's a stream of encoded bytes. I usually convert them to utf8. > You don't specify what you then do with this humongous string, Mainly I search for regex patterns which can span multiple lines. I could chunk it up if memory was an issue but a single read is just more convenient. Up until now it hasn't been an issue and to be honest I don't often hit multi-byte characters so mostly it will be single byte character strings. They are mostly research papers and such from my university days written on a Commodore PET and various early DOS computers with weird long-lost word processors. Over the years they've been exported/converted/reimported and then re-xported several times. A very few have embedded text or "graphics"/equations which might have some unicode characters but its not a big issue for me in practice. I was more just thinking of the kinds of scenario where big strings might become a problem if suddenly consuming 4x the storage you expect. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: string storage [was: Re: imaplib: is this really so unwieldy?]
On 26/05/2021 14:09, Tim Chase wrote: >> If so, doesn't that introduce a pretty big storage overhead for >> large strings? > > Yes. Though such large strings tend to be more rare, largely because > they become unweildy for other reasons. I do have some scripts that work on large strings - mainly produced by reading an entire text file into a string using file.read(). Some of these are several MB long so potentially now 4x bigger than I thought. But you are right, even a 100MB string should still be OK on a modern PC with 8GB+ RAM!... -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
string storage [was: Re: imaplib: is this really so unwieldy?]
On 25/05/2021 23:23, Terry Reedy wrote:
> In CPython's Flexible String Representation all characters in a string
> are stored with the same number of bytes, depending on the largest
> codepoint.
I'm learning lots of new things in this thread!
Does that mean that if I give Python a UTF8 string that is mostly single
byte characters but contains one 4-byte character that Python will store
the string as all 4-byte characters?
If so, doesn't that introduce a pretty big storage overhead for
large strings?
>
> >>> sys.getsizeof('\U0001')
> 80
> >>> sys.getsizeof('\U0001'*2)
> 84
> >>> sys.getsizeof('a\U0001')
> 84
Which is what this seems to be saying.
I confess I had just assumed the unicode strings were stored
in native unicode UTF8 format.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
https://mail.python.org/mailman/listinfo/python-list
Re: learning python ...
On 25/05/2021 00:41, Jon Ribbens via Python-list wrote: > What would you call the argument to a function that > returns, say, an upper-cased version of its input? Probably 'candidate' or 'original' or 'initial' or somesuch. Or even just 's'. Single character names are OK when there is no significant meaning to convey! But never a type name since the type could change or be extended (like bytes or even a user defined string subclass.) The exception being where it's a teaching exercise where the type is important, but even there I'd precede it with an article: aString, the_string or similar. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: learning python ...
On 24/05/2021 19:48, Grant Edwards wrote: >> Traceback ( File "", line 1 >> if = 1.234 >>^ >> SyntaxError: invalid syntax > > I must admit it might be nice if the compiler told you _why_ the > syntax is invalid (e.g. "expected conditional expression while parsing > 'if' statement"). Although wouldn't it be "expected boolean expression" rather than conditional expression? Python doesn't care how the argument to 'if' is arrived at so long as it's a boolean. And with assignment expressions, conditional expressions and literals all possible unambiguous error messages get harder and harder to figure out. But I do accept the general point that slightly more information about syntax errors would be nice. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: learning python ...
On 24/05/2021 16:54, Michael F. Stemper wrote: > In my early days of writing python, I created lists named "list", > dictionaries named "dict", and strings named "str". I mostly know better > now, but sometimes still need to restrain my fingers. I think most newbie programmers make that mistake. I certainly did when learning Pascal back in the 80's. But I was lucky, the tutorials were run by a guy who penalized bad variable names severely and took a half-mark off for every bad name. We very quickly learned to choose names that were descriptive of the purpose rather than the type. Its a lesson that I've never forgotten! -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: learning python ...
On 24/05/2021 07:21, hw wrote: >> Inside the function f() the name 'x" shadows the global "x"; references >> to "x" are to the function's local vairable. Which is very desireable. > > If it works that way, I would consider it an entirely different > variable. Remember that in Python variables are just names. They are literally keys to a dictionary and the value that is associated with the name can change. It may be a literal value, a function or a class or a type. Names can be anything that is not a reserved word. (Provided they keep within the naming grammar rules) Also, unlike some other languages, type names are not reserved words. by naming a variable like a variable type, I would think it is a bad idea for python to allow this without warning. It does warn you, that's what the message it printed said: print(isinstance(int, float)) TypeError: isinstance() arg 2 must be a type or tuple of types There is only on possible cause for that error. float is not a type or a tuple of types. Therefore you must have changed it somewhere. Since this is the first place in the program that python can identify an error, this is where the message gets printed. You are working in a dynamic language that allows you to do whatever you want to do. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: STARTUP FAILURE
On 13/05/2021 14:49, Sumukh chakkirala wrote: > Hello, I have been facing this " startup failure" for a while now, I can > open the IDLE from the programs that I have saved but I'm not able to open > the IDLE directly. Hope you can help me with this issue as soon as possible. > Usual questions: Which OS? Which python version? How exactly are you trying to open IDLE? And what happens? Any errors? How are you opening it "from the programs that I have saved" What exactly does that meaN? Right click in a File explorer program maybe? Have you tried other ways, such as from the command line? -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Start Python programming
On 27/04/2021 18:32, Gazoo wrote: > I'd like to start learning Python programming. What sites/tutorials > could you recommend for beginner, please. There is a getting started page on the python web site with links to guide you to many listed suggestions - books, web tutorials, video courses etc. https://www.python.org/about/gettingstarted/ Which one suits you best depends on many factors both objective and subjective. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: "py.ini" question
On 24/04/2021 15:23, Gisle Vanem wrote: > I have a question about the Python launcher; >c:\Windows\py.exe and the py.ini file. > > I have both Python 3.6 (32-bit) and Python 3.8 (64-bit) > installed. And I have a 'c:\Users\Gisle\AppData\Local\py.ini' > with this only: >[defaults] >python=3.6 I don't really use python on Windows so don't use this file. However, based on some of the other responses, what happens if you don't specify a version? ie. just type py -c "... And also what happens if you add an explicit python3 line as in Barry's example: [defaults] python=3.6 python3=3.6 As I say, pure speculation on my part. But if it helps... -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Ad-hoc SQL query builder for Python3?
On 24/04/2021 15:24, Rich Shepard wrote: > My web searches are not finding what I need to include in an application I'm > building: an ad-hoc sql query builder. > > End users will want to query their data for reports not included in the > built-in queries. I assume you understand the huge risks involved in such a tool. Letting users loose on their own data (and possibly other peoples) allows for huge potential damage/data loss etc. You can reduce the risk by finding ways to limit the access to read-only and tightly controlling which tables etc can be accessed. But many SQL builder tools don't do that and simply provide a way to create queries, including drop table, delete from etc. (Quite reasonably since they are usually aimed at DBAs rather than ordinary users) As a minimum ensure you have auto-backup processes in place every time the tool is opened. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: do ya still use python?
On 20/04/2021 04:47, Dan Stromberg wrote: > Actually, this list is less busy than it was a decade or two ago, but > that's probably because of things like stackoverflow, python-dev, pypy-dev, > cython-devel, python-ideas, distutils-sig, issue trackers, code-quality, > and probably others. > > There was a time when most python-related discussion happened here on > python-list/comp.lang.python. > It's also a reflection of Python's maturity in the market. It is no longer a cute language that folks stumble across and need lots of support to get up and running. There are all sorts of formal and informal training routes available. People are far more likely to have a buddy at work using Python that they can ask stuff. We see the same trend on the tutor list, traffic has dropped off by a factor of 3-5 times what it was at its peak. And the questions are changing too, fewer basic things about loops and writing functions, more about specific library modules and such. (That's why I now have time to regularly read this list instead of dipping in once or twice a month! :-) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Ann: New Python curses book
On 14/04/2021 19:55, Rich Shepard wrote: > On Wed, 14 Apr 2021, Alan Gauld via Python-list wrote: > >> The paper version should be fine (apart from one error on p44 which has >> now been fixed!). > > Alan, > > What's the error and correction so I can change it in my dead tree version? > > Rich In the main() function the block of code starting with the 'with' statement should be indented to be part of main(). It has been left at the outermost indentation level. The source code file is correct so check against that. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: port to PDOS (especially mainframe)
On 14/04/2021 11:35, Paul Edwards wrote: > I have succeeded in producing a Python 3.3 executable ... > However, the executable doesn't work yet. Late to this party but how big is the assembler? It might be easier to translate the Python to C! I've done that in the past and with the aid of a few functions to mimic common Python constructs (dicts, foreach() etc) it was verbose but not too painful. If its <5K? lines of Python it might be easier. Just a thought. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Ann: New Python curses book
On 30/03/2021 12:12, Alan Gauld via Python-list wrote: > I've just published, in Kindle and paperback formats, I've just noticed that the kindle version has several indentation problems in the code listings. I can't do anything to fix it because it is all perfectly aligned in the Word file I submit, it's caused somewhere in the Amazon conversion process. (In fact it's possibly its OK on some Kindle devices/apps, just not the web reader I was using!) Hopefully the expected readership will be smart enough to: a) figure it out from the context and b) download the sample code which is correctly formatted. The paper version should be fine (apart from one error on p44 which has now been fixed!). Apologies to anyone who got stung by this. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: UI design: combobox or radiobuttons?
On 13/04/2021 22:53, Rich Shepard wrote: > While a set of radiobuttons occupies more room on the parent widget than > does a combobox are there any technical or user issues that would suggest > using one over the other? readability? If the combo box puts the units immediately beside the value then it will be more readable than if it is a row of radio buttons above/below or beside the value. But if the radio buttons represent a unit choice that applies to all values on the screen then that is more noticeable and thus more readable than a single small combobox choice lurking in a corner somewhere. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Ann: New Python curses book
On 12/04/2021 00:53, Daniel Nelson wrote: >> (It should be available in most other Amazon stores too) > > This looks handy, I'd love to buy a copy but I don't do business with > Amazon if I can avoid it. Any chance this will be available from other > locations? I tried to publish it on several open-source web sites but none of them responded to me so I went with Amazon as the commercial site most people turn to first and with the widest reach. Also the Amazon publishing tools are very easy to use. However, one of their conditions for low cost books is exclusivity, so no it won't appear anywhere else unless I increase the price significantly which I don't want to do. What I might do is host the original translation of the C document as a PDF on my own web site. But that's not likely to show up in many searches! If I get round to that I'll announce it here. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: How to access a variable from one tab in another tab of a notebook?
On 08/04/2021 06:01, Mohsen Owzar wrote:
>> But this is why GUIs are often(usually?) built as a class
>> because you can store all the state variables within
>> the instance and access them from all the methods.
>>
>> You can do it with functions but you usually wind up
>> with way too many globals to be comfortable.
> Because I'm a newbie in Python and write programs since
> a couple of months, and I'm not so familiar with classes,
OK, In that case you should probably read up on classes
and play around with them to get used to the ideas of
classes, objects and methods.
You can carry on using functions but you will need to
keep track of quite a lot of global variables which
can get messy in bigger programs. Classes just keep
things a bit more tidy.
> would be very nice to give me a code, how I have to
> change my code into a class form.
> I tried without a class and I ran into problems that
> the defined frame and entry are not defined.
One of the problems in your code is that you are not
storing references to the widgets you create. You are
relying on the containment tree to store the references
and keep them alive. But that makes it difficult to
access. As a general rule of thumb if you are creating
any widget that responds to events you should keep
a reference to it - ie. create a variable.
For example in your code you have a section like this:
def gen_t2(frame):
def getValue(event):...
lbl = Label(frame, text='Val').pack()
ent = Entry(frame)
ent.pack()
ent.insert(0, '2')
ent.bind('', getValue)
And you call it like this:
if firstTime2 == 1:if firstTime2 == 1:
gen_t2(tab2)
firstTime2 = 0
gen_t2(tab2)
firstTime2 = 0
Inside the function you store a reference to the Entry as ent.
but ent disappears as soon as the function ends, you cannot
use ent to access your entry outside the function.
You need to return the widget like so:
def gen_t2(frame):
def getValue(event):...
...
ent.bind('', getValue)
return ent
And then call it like:
if firstTime2:
entry_field = gen_t2(tab2)
firstTime2 = False
Now you can access your Entry field via the global
variable entry_field.
I suspect you should forget about the classes for now, focus
on getting the functions to work, especially returning values
and storing those in global variables that you can access from
elsewhere. These principles are just as important when you
get round to studying classes later.
And remember that global variables in one module can be
accessed from another module by importing the first module
into the second and using the module name as prefix.
import tab2
txt = tab2.entry_field.get()
HTH
You might also find the functions, namespaces and GUI sections
of my tutorial useful (see below).
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
https://mail.python.org/mailman/listinfo/python-list
Re: How to access a variable from one tab in another tab of a notebook?
On 07/04/2021 09:35, Mohsen Owzar wrote:
> The problem is that I can't use the variable "val" from Tab2 in Tab 1,
> # Filename: Tab1.py
> from tkinter import *
>
> def gen_t1(frame):
> f = LabelFrame(frame, text='f', bg='lightgreen')
> f.pack(expand=True, fill='both')
>
> b1 = Button(f, text='B1').pack()
>
> ## if val > 5:
> # Filename: Tab2.py
> from tkinter import *
>
> def gen_t2(frame):
> def getValue(event):
> val = ent.get()
> print(val)
Note that val is a local variable within a nested function.
It only exists while the nested function is executing.
As soon as the function ends val is thrown away.
If you want the value of the entry you need to store it
in a variable that is visible after the function exits
(by returning it perhaps? or setting a global - ugly)
But you still have the problem of making that visible
to Tab1. You could import tab2 into tab1 and use Tab2.varName
But this is why GUIs are often(usually?) built as a class
because you can store all the state variables within
the instance and access them from all the methods.
You can do it with functions but you usually wind up
with way too many globals to be comfortable.
> from Tab1 import gen_t1
> from Tab2 import gen_t2
...
> def on_tab_change(event):
> global firstTime1, firstTime2
>
> tab = event.widget.tab('current','text')
> if tab == 'Tab 1':
> print('Tab 1')
> if firstTime1 == 1:
> gen_t1(tab1)
> firstTime1 = 0
Probably nicer to use boolean values for
firstTime1 and firstTime2, ie True and False
rather than their numeric equivalents.
HTH
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
https://mail.python.org/mailman/listinfo/python-list
Re: Horrible abuse of __init_subclass__, or elegant hack?
On 02/04/2021 21:33, dn via Python-list wrote: > Bournville was the only Cadbury chocolate I would > consider. Today, even that seems to lack Cadbury has always been a budget chocolate brand(*) here; its a mass market option loaded with sugar and little else. Certainly doesn't compare to Suchards, Lindt, Nestle or Green & Black, or even Lidl's own brand: Fin Carre (especially their "Rich Dark" milk choco! ). (*)I'm guessing Hershey is the equivalent stateside? > conversation) it is worth noting that the Cadbury brothers had some > ideas about caring for workers/contributors in similar manner to PSF's > interests in egalitarianism and diversity - certainly a quality-of-life > beyond those of the often quoted 'advances' credited to Henry Ford. Indeed, social engineering that to some extent still exists today. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Friday Finking: initialising values and implied tuples
On 02/04/2021 23:10, dn via Python-list wrote: > When there are several items to be defined and initialised, how do you > prefer to format the code, and why? > (a) basic linear presentation: > > resource = "Oil" > time = 1 > crude = 2 > residue = 3 > my_list = "long" In production code I'd almost always go with this one. It's the only option that both keeps the variable and value together and allows me to add an explanatory comment if necessary. > (e) implicit tuples: > > resource, time, crude, residue, my_list = "Oil", 1, 2, 3, "long" Occasionally, and in personal code, I'll use this. Although this would be about as many items I'd ever have in one list. But in production code, if items are related, I'd use it. eg. x,y = 42,50 # starting coordinates hour,min,sec = 0,0,0 # default start time But in both those cases I'd more likely define a variable to be a tuple: eg. start = (42,50) # starting coordinates -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Horrible abuse of __init_subclass__, or elegant hack?
On 02/04/2021 00:42, dn via Python-list wrote: > Contrarily "tuck" in (old) English slang represented "sweets" (or Not that old. We still use it occasionally today. And we certainly had a "tuck shop" at school. It was where you bought lunch if not eating in the refectory. ie. sandwiches, crisps, pop etc. But its main sales were sweets including chocolate bars (bringing us back to Cadbury :-) Unusually, our tuck shop was run by the student body. The school prefects were the operating committee and responsible for finding volunteers to staff it and order supplies and bank the proceeds 9with the school secretary) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Horrible abuse of __init_subclass__, or elegant hack?
On 01/04/2021 00:14, Chris Angelico wrote: > On a scale of 1 to "submit this to The Daily WTF immediately", how bad > is this code? :) The only worthwhile test of code quality is whether a new member of the team, competent in the language but not an expert can understand the code in two readings or less. If they can it's good enough. Maintenance is always the highest cost in any significant project so good code must be maintainable. In this case I'd venture they'd encounter init_sublass() for the first time, do some research and on the second reading make sense of it. So, it's good to go. Whether it's an optimal design or not is a different matter. There's always more than one way to do it. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Source code link was: Re: Ann: New Python curses book
On 31/03/2021 00:09, Alan Gauld via Python-list wrote: > Watch this space. Hopefully tomorrow. The source code is now available in a zip file at: http://www.alan-g.me.uk/hills/PythonCursesCode.zip Or via a link on the programming section of my home page http://www.alan-g.me.uk/ It is licensed using a Creative Commons license. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: New Python curses book
On 30/03/2021 20:05, Brian Oney via Python-list wrote: > Congratulations! > > Indeed, I was wondering for a moment if this was a guide to al dente > spaghetti code. With each curse being a funny way to mess with the colleagues > performing the code review ;) You may jest but I originally titled it "Programming Python with curses" And changed it precisely because I thought it might be misunderstood :-) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Ann: New Python curses book
On 30/03/2021 19:52, Grant Edwards wrote: > It is. I just bought the kindle version on the US site, and it renders > fine in the cloud reader. It would be cool if you could cut/paste code > examples from the book into IDLE or a text editor, but I've never been > able to get the cloud reader to allow that sort of thing. Blast! You just reminded me I meant to add a link to where the source code zip lives! (Or will live once I put it there) I'll do an update of the kindle book but I don't know if you can get the update for free... I'll also post the zip file url here once I've put it up. Thanks for that reminder. As for cut n paste, the requirement to write in MS Word and convert to PDF/Kindle means that quotes etc get all messed up. And as for Python indentation I shudder to think. That's why I intended to put the source code up. Watch this space. Hopefully tomorrow. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: memory consumption
On 30/03/2021 16:50, Chris Angelico wrote: >> A 1GB process on modern computers is hardly a big problem? >> Most machines have 4G and many have 16G or even 32G >> nowadays. >> > > Desktop systems maybe, but if you rent yourself a worker box, it might > not have anything like that much. Especially if you need to have > multiple of them. Rental servers on the cloud. Now that's after my time. The last server I used had 128GB and anything less than 32GB wasn't worthy of the name. I forget you can rent virtual servers for pennies these days! :-) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: Ann: New Python curses book
On 30/03/2021 17:14, Grant Edwards wrote: > Is the kindle format readable via a web browser pointed at > read.amazon.com (AKA "Kindle Cloud Reader)? It seems to be, I downloaded the free sample and could read the first 2 chapters on the web reader. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Ann: New Python curses book
I've just published, in Kindle and paperback formats, my book on "Programming curses with Python". https://www.amazon.co.uk/dp/B091B85B77/ (It should be available in most other Amazon stores too) It is a complete rewrite of the Linux Documentation Project's HowTo for the C ncurses library. It has the same structure but all-new text and several new chapters. All specific to the Python curses package. I've kept the prices as low as Amazon permits (and allowing for fluctuations in their costs). As such, I will therefore make a few cents profit per book from sales (full disclosure). However, I felt this was the easiest and most effective way to get it "out there" where it could be found. I hope it's useful to somebody. Special thanks to all who provided me with feedback on its various iterations, especially Alex Kleider and Bob Stepp who stuck with it right to the end. Thanks guys. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: memory consumption
On 29/03/2021 11:12, Alexey wrote: > Hello everyone! > I'm experiencing problems with memory consumption. > The first thing you really need to tell us is which OS you are using? Memory management varies wildly depending on OS. Even different flavours of *nix do it differently. However, most do it effectively, so you as a programmer shouldn't have to worry too much provided you aren't leaking, which you don't think you are. > and after second run it weighs 1Gb. If I will continue > to run this class, memory wont increase, so I think > it's not a memory leak, but rather Python wont release > allocated memory back to OS. Maybe I'm wrong. A 1GB process on modern computers is hardly a big problem? Most machines have 4G and many have 16G or even 32G nowadays. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: convert script awk in python
On 24/03/2021 16:00, Avi Gross via Python-list wrote: > But I wonder how much languages like AWK are still used to make new programs > as compared to a time they were really useful. True. I first discovered awk from a Byte article around 1988/9 and it became my goto tool for text munching right up until I found Python in 1998. I still use it as part of a unix command pipeline but I rarely write awk scripts in a file anymore - if it's that complex I reach for Python. But at one time I had a dozen or more awk scripts in my ~/bin folder. I also used awk on a real-world project to process csv files from an Excel spreadsheet and create site-specific config files for some shiny new WindowsNT(v3.1) boxes we were using. They had twin network connections and hard coded IP settings(for resilience) and the network designers delivered the site settings by Excel. We turned them into .BAT files using awk. Eventually, we figured out how to write Excel macros and converted it all to VBA. Happy days. :-) -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: convert script awk in python
On 23/03/2021 14:40, Avi Gross via Python-list wrote:
> $1 == 113 {
> if (x || y || z)
> print "More than one type $8 atom.";
> else {
> x = $2; y = $3; z = $4;
> istep++;
> }
> }
>
> I am a tod concerned as to where any of the variables x, y or z have been
> defined at this point.
They haven't been, they are using awk's auto-initialization feature.
The variables are defined in this bit of code. The first time we see $1
== 113 we define the variables. On subsequent appearances we print the
warning.
> far as I know has not been called. Weird. Maybe awk is allowing an
> uninitialized variable to be tested for in your code but if so, you need to
> be cautious how you do this in python.
It's standard behaviour in any POSIX compliant awk, variables are
initialised to empty strings/arrays or zero as appropriate to first use.
The original AWK book has already been mentioned, which covers nawk.
I'll add the O'Reilly book "sed & awk" which covers the POSIX version
and includes several extensions not covered in the original book. (It
also covers sed but that's irrelevant here)
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
--
https://mail.python.org/mailman/listinfo/python-list
Re: .title() - annoying mistake
On 19/03/2021 19:58, Dan Stromberg wrote: > In high school, I was taught that English has multiple capitalization > rulesets to choose among for titles. > And, of course, there are multiple forms of English. English English is very different from US English. And even in the UK there are (a few, minor) differences between usage in Scotland compared to England, for example. Trying to write programming languages to follow natural language semantics and grammar is an exercise in frustration. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: How do I read .csv files
On 16/03/2021 16:15, The Cool Life wrote: > Try importing the CSV module. That might help! And for the removal of doubt it is spelled csv 9lower case) And it looks like you want to read about the DictReader class within it. The csv module docs include several examples. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: REPL peculiarity
On 11/03/2021 11:01, Rob Cliffe via Python-list wrote: > This is a valid Python program: > > def f(): pass > print(f) > > But at the REPL: > > >>> def f(): pass > ... print(f) > File "", line 2 > print(f) > ^ > SyntaxError: invalid syntax > > It doesn't seem to matter what the second line is. In the REPL you have > to leave a blank line after the "def" line. Why? I guess just because that's how the interpreter is written. It looks for a blank line to terminate the function definition. It does the same with multi-line definitions too. I agree it would be possible in the case of single line definitions to forego the blank line but it doesn't. It does remind you that you need another line since it shows the secondary prompt ... instead of the primary >>> -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
Re: python curses constant names for mouse wheel movements?
On 09/03/2021 01:05, pjfarl...@earthlink.net wrote: > I am replying to my own message due to the digest not appearing in my inbox > yet today. I will add Alan Gould's responses and my reply to him manually. > Yes, when I talk about wheel up/down I do mean wheel rotation events, not > wheel-button-down or up click events. The latter are correctly reported by > the PDCurses implementation used by windows-curses V2.2.0 as BUTTON2 events. > > Christoph Gohlke gave me this link to the current-version PDCurses > implementation definitions for the mouse state constants, which I found very > helpful: > > https://github.com/wmcbrine/PDCurses/blob/master/curses.h#L199 > > The PDCurses names defined there are exactly what I needed to see, even if > the current cpython and windows-curses implementations do not support them > quite yet. I can safely define them myself and adjust my code as later > releases of cpython and windows-curses are updated to support them natively. Thanks, I've done some tests and I see the events as WHEEL FORWARD - 0x1 or curses.BUTTON4_PRESSED WHEEL BACK- 0x20 but not defined in the curses module That's using ncurses on Linux. Do you get the same mask value under PDcurses on Windows? I suspect in the real world I'd probably create my own definitions as WHEEL_FORWARD and WHEEL_BACKWARD just for readability. > This link to an ncurses man page concerning mouse events is also > instructive: > > https://invisible-island.net/ncurses/man/curs_mouse.3x.html Thanks for that, I hadn't spotted that there was a mouse man page before... -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos -- https://mail.python.org/mailman/listinfo/python-list
