[Tutor] Iterating a dict with an iteration counter? How would *you* do it?
List,
Simple question: Is there a common pattern for iterating a dict, but also
providing access to an iteration counter? Here's what I usually do (below). I'm
just wondering if there are other, more clever ways::
data = {'a': apple, 'b': banana, 'c': cherry}
i = 0
for k,v in data.items():
print(i: %s, k: %s, v: %s % (i,k,v))
i += 1
Another variant, same idea::
data = {'a': apple, 'b': banana, 'c': cherry}
for i,k,v in zip(range(len(data)), data.keys(), data.values()):
print(i: %s, k: %s, v: %s % (i,k,v))
How would you do it?
-Modulok-
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Re: [Tutor] Iterating a dict with an iteration counter? How would *you* do it?
Hmm.. no kidding. Well, at least I knew I was over-complicating it.
Cheers!
-Modulok-
On 2/4/13, Dave Angel da...@davea.name wrote:
On 02/04/2013 12:13 PM, Modulok wrote:
List,
Simple question: Is there a common pattern for iterating a dict, but also
providing access to an iteration counter? Here's what I usually do
(below). I'm
just wondering if there are other, more clever ways::
data = {'a': apple, 'b': banana, 'c': cherry}
i = 0
for k,v in data.items():
print(i: %s, k: %s, v: %s % (i,k,v))
i += 1
Another variant, same idea::
data = {'a': apple, 'b': banana, 'c': cherry}
for i,k,v in zip(range(len(data)), data.keys(), data.values()):
print(i: %s, k: %s, v: %s % (i,k,v))
How would you do it?
-Modulok-
enumerate()
for i, (k, v) in enumerate(data.items()):
--
DaveA
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Re: [Tutor] optparse.OptionParser options in alphabetical order in help display
Does anybody know if there is a way to make --help option to display options in alphabetical order? I know this sounds like spam and doesn't answer your question, (sorry!) but you should check out the third part module 'docopt'. It is *extremely* simple and a lot more flexible. It made me actually want to write command line interfaces again. http://www.youtube.com/watch?v=pXhcPJK5cMc http://docopt.org/ Again, sorry for the spam but everyone I've shown has switched and were glad they did. It's also on PyPi and github. In fact, the github page is probably the best place to check it out. -Modulok- On 12/18/12, rail shafigulin rail.shafigu...@gmail.com wrote: Does anybody know if there is a way to make --help option to display options in alphabetical order? Right now it displays options in the order I added them. I'm using Python 3.1 Any help is appreciated. Thanks. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] code to generate my own text captchas
On 10/24/12, Tsila Hassine tsila.hass...@gmail.com wrote: Hello all, I am looking for simple python code that will take a given string and distort it, captcha like. it is for artistic purposes, so no verification required. I just need the image q text distortion code. Thanks!!! tsila You might look into writing a shell script or even python script wrapped around ImageMagick. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Passing arguments to running a python script on a remote machine from a python script on local machine .
I forgot you need to escape special characters in the arguments. You can add quoting and escape special characters at the same time with the undocumented function pipes.quote: import pipes args = tuple(pipes.quote(arg) for arg in (arg1, arg2, arg3)) cmd = 'python test.py %s %s %s' % args Notice there are no longer quotes around each %s in cmd. Python 3.3 will have shlex.quote: http://docs.python.org/dev/library/shlex.html#shlex.quote Why is ``pipes.quote`` undocumented? It's useful. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] [Semi-OT] Yes or no on using a Graphical IDE?
Hey all, not trying to contribute to the flames of one graphical IDE over another. I'm just trying to figure out if they are worth the learning curve? I have been doing most of my work in vi and the graphical IDE I'm supposed to use for a class keeps adding crap that I have to erase, and I have to move my hands to use the GUI parts instead of just typing. Is there a point in which a GUI IDE becomes more of a help than a hindrance? Thanks! Leam Leam, It's really a personal taste. I can't speak for others, but this is my basic setup: I use a highly customised graphical text editor (jEdit) with several plugins specific to what I'm doing. I guess it kind of equates to a lightweight IDE. I combine this with an ssh connection to a FreeBSD box for all the wonderful *nix command line tools, scripts, debuggers, etc that are out there. I like the idea of an IDE, but haven't met one I really care for. I much prefer a GUI editor over a purely console based one. That is, I like the ability to use a mouse to aid in quickly moving text around. I also like the sub-pixel anti-aliased fonts that you don't always get on a console. (Of course, this depends on the console.) You can do most things with command line editors, (some even support using a mouse) but I never found it to be as fast. Again, it's personal and I'm probably getting off the subject. This is more of a console vs. GUI debate. I short, I'd say use whatever you're comfortable with. After that, use what your friends/co-workers use. The popup auto-complete for class names or variable names in IDE's is nice and can often save you from having to look something up, but it isn't critical. Console tools like ipython can make up for some of that, but even so that's not something I generally write code in. Perhaps others have more insight. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Does anyone use UML?
List, Does anyone use UML (Unified Modeling Language) with python? If so, what tools do you use? Is it worth the added effort? -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Genetic module recommendations?
List, I'm looking for a good genetic module. (Stable, well documented, pythonic, etc.) I'm writing a breeding simulator where users select parent organisms to breed based on traits they favor, e.g: eye color, height, etc. The human player is the fitness function. I guess this is artificial selection? After breeding the user gets an offspring which carries traits from its parents. It's only a game and a crude approximation of nature at best. However, the algorithm has to be stable enough this can go on for several hundred generations without entropy reducing to the point of haulting evolution. On the other hand, I don't want so much entropy that it's reduce to a random search. Before I write my own, I thought I'd ask to see if there was a third party, de-facto standard Python genetic module. Or at least one that is highly recommended. Any suggestions? Thanks! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] specifying my default python installation
On 8/17/12, debbym de...@glance.net wrote: I am new to both freebsd and python. I have python 2.6 and 3.2 both installed on freebsd. python runs python 2.6 and I need to use python3.2 to run python 3.2 Do I need to do something to make python 3.2 the default? FreeBSD doesn't have an 'alternatives' system like debian flavors. However, there's nothing wrong with your install. I run FreeBSD on several boxes. On this box I have python 2.6, 2.7, and 3.2 installed. My default 'python' executable is a symlink that points to /usr/local/bin/python, which itself is version 2.6. (The box I'm on is FreeBSD 8.1) If I want a program to run in python3.2, I put something like this (or similar) as the shebang line at the top of the file: #!/usr/bin/evn python3.2 Or to get the interpretter just type 'python3.2'. Don't worry about the shebang lines being cross platform either; Once you package up your scripts into python packages, using distutils or similar, all shebang lines will be stripped. Upon re-installation on the target platform they'll be replaced appropriately. (In fact, some platforms even put 'env' in /bin instead of FreeBSD's /usr/bin.) I would also recommend against changing the default 'python' symlink, as some tools may depend on it being at a specific version. One I can think of off the top of my head is the third party `xps` tool for searching ports. This is most notable when talking about python2.x vs. the 3.x branch, as python 3 broke backward compatibility with things like print statements becoming print functions. If you find it irritating to have to type 'python3.2' instead of just 'python', you could create an alias for your shell, so that 'python' is aliased to 'python3.2'. I use tcsh, so I in my case my $HOME/.cshrc file might look something like this: alias python /usr/local/bin/python3.2 Then I would type 'source .cshrc' or logout and back in for changes to take affect. As an alternative, you could create a symlink from your own bin directory instead. For example: cd mkdir bin ln -s /usr/local/bin/python3.2 ./bin/python This should work once you type 'rehash' (in tcsh) or logout and log back in. Most default installs will list the 'bin' directory, found in a given user's home directory, on the default $PATH. You can verify this by typing 'echo $PATH' and making sure '/home/you/bin' is listed. This isn't as good of an option as simply using the alternate shebangs, as it affectively replaces your version of python with the version you choose, but it will work. Finally, if you want to get carried away, you can install a virtual python as mentioned. For even more options, you might subscribe to questi...@freebsd.org ;) -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confusion with Python, Bash and Command Prompt
... My Question: Is it true that doing that is as same as doing #!/usr/bin/env python on Unix? Because I think that the matter of shebang is limited to Bash and Windows don't have a bash, it has a Command Prompt. And I don't think such thing happens in Windows. It has nothing directly do with bash. It has to do with the operating system's 'program loader'. It's the low level code responsible for setting up an execution environment for a new process. It looks for environment variables, etc. For example on FreeBSD most shebang parsing defined in envopts.c. Basically, whenever you request a file to be executed, the program loader (not your shell) looks at the first line of the file for a shebang. If found, it executes the file the shebang line references and passes the path to the current script file as the first argument. That said, different operating systems' program loaders', regardless of the shell you're using (be it bash, tcsh, sh, etc), will process shebang lines differently. Some ignore them entirely. The syntax can even vary slightly from one OS to another (and not just the file paths). So does it apply to Windows? No. Windows has no concept of shebang lines. File types are determined exclusively their extensions, as is the executability of a file. (There's a registry looking that occurs to determine what program to pass the file to.) If you rename a python script from foo.py to foo.jpg, windows will attempt to open it in an image viewer, regardless of any shebang lines present. (Contrast this with most unix-like flavors where extensions are meaningless. Executability is determined by a file-system level permission bit and the interpreter is determined by the program loader reading shebang lines. The file would be passed to the python interpretter, assuming a correct shebang.) You are right in your assumption; It does not apply to Windows. The tutorial is incorrect. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] While learning Py: To IDE or not to IDE?
Since you are using Solaris, I expect your options for IDEs are limited. You're probably best off using Unix as your IDE: http://blog.sanctum.geek.nz/series/unix-as-ide/ which is my preferred solution. There's very little I can't do between my editor and a terminal window with a few tabs open. Apparently I'm not alone. I've not found an IDE I liked much either. They all feel kind of bloated with 37+ useless features I don't need. Instead, I use jEdit, a few choice plugins and an ssh connection to a command shell on a FreeBSD file server. (The fact that jEdit was written in java is irritating form a licensing perspective on some OS's but the editor itself is top notch.) A decent editor combined with a good command shell is all I've ever needed. If I'm on the console alone, for minor editing I just use nano. Personally, and this is just me, I've felt that big IDE's add a lot of interface and fluff but not a lot of substance. One of the benefits of learning a few basic editors and how to really use a command shell, is that it doesn't matter what brand of linux/BSD/unix you're on, you're still pretty much at home. That said, IDE's still have their place, especially when writing a lot of GUI stuff. Learning to use a command line at first feels really clunky and primitive, but eventually it eclipses most GUI's and IDE's in terms of speed and the tools available. You can also ooze right into system administration without much effort. But again, that's just me :p -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] TypeError: 'int' object is not callable
On 5/16/12, Greg Christian glchrist...@comcast.net wrote: Can anyone tell me what I am doing wrong here. When trying to call the factors function from main with x = factors(Tn), getting the error message: “TypeError: 'int' object is not callable”? Any help would be appreciated. Thanks. def factors(n): L = [] for i in range(1, int(n ** 0.5) + 1): if (n % i == 0): L.append(i) return L def main(): factors = 0 counter = 0 L = [] while len(L) 50: counter += 1 L.append(counter) Tn = sum(L) x = factors(Tn) #print x print(sum(L)) if __name__ == '__main__': main() You declared 'factors' as a variable on line 1 in main:: factors = 0 This masks the call to the function 'factors'. You get the error because you assigned factors an integer and you cannot 'call' an integer. The easiest solution is to use another name for the variable 'factors' instead. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Is there space a between #! and /usr/bin/env python ?
On 5/1/12, Santosh Kumar sntshkm...@gmail.com wrote: Its getting complicated now. Will it effect or not? No. It won't. Spaces between '#!' and '/foo/bar/whatever' are ignored. Long Answer: Don't worry about it. For example, on one of my Ubuntu linux boxes there's 69 rc files shipped with the OS that use the variant: '#! /bin/sh' (with space). And there's 26 that use the variant '#!/bin/sh' without a space; It really doesn't matter. (For the curious, you can find out like this):: grep --ignore-case --regex '^#!/. *' --recursive /etc/rc* | wc And this respectively:: grep --ignore-case --regex '^#!/.*' --recursive /etc/rc* | wc On my FreeBSD server all files shipped with the OS don't uses spaces. They're just '#!/bin/sh'. However, some of my own scripts do, and they work regardless. i.e. It doesn't really matter. On Windows they're ignored entirely. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to have the name of a function inside the code of this function?
On 4/6/12, Karim kliat...@gmail.com wrote: Hello all, I have : def foo(): print( getattr(foo, 'func_name')) Where I get the name of the function but I add to give the name of this function. Indeed it is not very helpful... I checked the globals() but how I can do to get globals()['toto'].func_name. This is not more helpful ;o) If you have any idea to get the caller name inside the caller. The following works, but only on implementations which provide stack frame support. As the docs kindly point out: ...this isn't guaranteed to exist in all implementations of Python. Example code: import inspect def foo(): '''Print my own name.''' frame_info = inspect.getframeinfo(inspect.currentframe()) print(frame_info.function) foo() That said, there's probably a better way to solve whatever bigger problem you're trying solve. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] breeds of Python .....
After following the reading suggestions, I soon found myself looking at quite a few code examples that would only run under a particular version of python. Finally, I converted the example that I was working on to run under Python3. I just wondered if you guys would advise a newbie like me to concentrate on Python3 or stay with Python2 and get into bad habits when it comes to change eventually? Apart from the print and input functions, I haven't so far got a lot to re-learn. Kind regards,Barry. Barry, If you're just starting out, go with 3.x. If you have a need for some third party modules that aren't yet available for 3.x, you'll have to stick with 2.x. Most beginner tutorials will work without changes, except for the print statement is now a function, e.g: print foo Is now: print(foo) There isn't a whole lot of difference in syntax to learn. Some modules have been renamed, some module functions re-worked, etc. Probably the biggest change is the move to all unicode strings. One thing you can do if you're running 2.x but want to get into the 3.x swing of things is turn on 3.x warnings. It will tell you if you did something the 2to3 tool can't automatically fix: python2.6 -3 If you want, you can actually use the 3.x style print function and true division when using 2.x by putting this at the top of your code:: from __future__ import print_function from __future__ import division Now in 2.x, just like 3.x this will raise an exception: print foo #-- Now fails in 2.x print(foo)#-- Works. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Syntax error help
On 3/30/12, chris knarvik x23ch...@gmail.com wrote:
Alright i have been trying to right a (relatively) simple to calculate area
and volume below is my current working code
def areamenu():
print 'Square (1)'
print 'triangle (2)'
print 'rectangle (3)'
print 'trapazoid (4)'
print 'circle (5)'
def squareacalc():
sidelength = input('enter side length: ')
print ' the side length is' sidelength ** 2
def displaymenu():
print 'please make a selection';
print 'Area (1)';
choice = input(raw_input('enter selection number'):
if (choice == 1):
Areamenu():
else:
print 'choice' , choice, ' is wrong try again'
def selctiona():
Areamenu();
choicea = input(raw_input'enter selection');
if (choicea == 1):
squareacalc()
print 'good bye'
I keep getting this error
Traceback (most recent call last):
File pyshell#3, line 1, in module
import Area
File C:\Python27\Area.py, line 10
areamenu()
^
SyntaxError: invalid syntax
can anyone tell me what im doing wrong i cant see the problem
help would be appreciated
Chris,
Your code has numerous problems. First, the only lines that should end in a
colon ':' are lines that define something, i.e. class and function signatures,
etc. Your code has them sprinkled in places where they really don't belong. For
instance:
choice = input(raw_input('enter selection number'): #-- No.
Additionally, python statements are almost never terminated with a semicolon
';'. Your code has those in random places as well. Python statements *can* be
semicolon terminated, but this should *only* be used if there is more than one
statement per line. (Generally a discouraged practice, unless in the case of a
list comprehensions):
choicea = input(raw_input'enter selection'); #-- Not needed.
The other problem I see is a lot of mis-matched parentheses. For instance your
code has places where there are two opening parentheses, but only one closing
parenthesis:
choice = input(raw_input('enter selection number'):
Should be:
choice = input(raw_input('enter selection number'))
However, the above line is pretty nasty. It's making an unnecessary function
call. Above, its waiting for user input to the 'input' function, and using the
return value of the 'raw_input' function for that input, which itself is
waiting for user input. i.e. an input waiting for an input. It should instead
be something like this:
choicea = input('enter selection: ')
*If* you decide to use the 'raw_input()' function instead, remember to
type-cast the value that gets entered. By default with 'raw_input()' it is
interpreted as a string and not an integer. Thus, the comparison 'if (choicea
== 1)' wouldn't work with 'raw_input()' expected.
This is a problem as well:
print ' the side length is' sidelength ** 2
The print statement only takes a single argument, or multiple arguments *if*
they are comma separated, e.g:
print ' the side length is', sidelength ** 2
However, this whole thing would be better written using string substitution::
print ' the side length is %s' % (sidelength ** 2)
This is also incorrect:
Areamenu()
Your code defines a function named 'areamenu', not one named 'Areamenu'.
Remember, python is case sEnsItiVe. e.g: Foo() and foo() are different.
Good luck!
-Modulok-
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Re: [Tutor] tabbed output
On 2/12/12, Michael Lewis mjole...@gmail.com wrote:
I am having a weird issue. I have a print statement that will give me
multiple outputs separated by a tab; however, sometimes there is a tab
between the output and sometimes there is not. It seems sort of sporadic.
My code is below and two sample outputs are below that (one that works how
I expect, and the other showing the issue (tab separation not occurring
between all pieces of the output) What is going on?
def CheckNames():
names = []
for loop in range(1,4):
while True:
name = raw_input('''Name #%s: ''' %(loop))
if name not in names:
names.append(name)
break
print '%s is already in the data. Try again.' %(name)
sorted_names = sorted(names)
for element in list(sorted_names):
print 'Hurray for %s!\t' %(element),
Sample Output1:
Name #1: mike
Name #2: bret
Name #3: adam
Hurray for adam!Hurray for bret! Hurray for mike!
Sample Output2(there is a tab between output 2 3, but not 1 2):
Name #1: abe
Name #2: alan
Name #3: adam
Hurray for abe! Hurray for adam! Hurray for alan!
You should use spaces, not tabs. Tabs only align with tab stops, which will
depend on the length of the words (names). To make it easy to use spaces
instead, use the 'format()' method available on string objects. A one-line
modification of your could would look like this::
def CheckNames():
names = []
for loop in range(1,4):
while True:
name = raw_input('''Name #%s: ''' %(loop))
if name not in names:
names.append(name)
break
print '%s is already in the data. Try again.' %(name)
sorted_names = sorted(names)
for element in list(sorted_names):
print {value:30}.format(value=Hurray for %s! % element),
# The line above is all that was changed.
The result, is that 'value' will be output as left-aligned '', and a minimum
of 30 characters wide '30'. The 'value' is specified as a keyword argument to
the format() method. In the example above, 'value' is also making use of
python's older string formatting method. Using a monospaced font, your output
will always be lined up, as long as the 'value' string never exceeds 30
characters wide.
You can optionally *not* specify the 'value' variable and instead use a
positional argument to the format method like this, but it makes it less clear
what you're doing::
print {0:30}.format(Hurray for %s! % element),
As a final note, if 'CheckNames' is a function and not a method, it should be
all lowercase, or use_underscores rather than camelCase. This is not enforced
by python, but is kind of the de-facto standard.
Read more about the format method here:
http://docs.python.org/library/string.html#formatspec
http://docs.python.org/library/string.html#formatstrings
-Modulok-
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Re: [Tutor] Python Database Scripting
The closest thing you'll find will probably be the third party module 'sqlalchemy'. You can install it via easy_install or pip. If that doesn't meet your needs I'm not sure what else would. (But would love to hear about it.) -Modulok- On 2/8/12, Brad Hudson brad.hud...@gmail.com wrote: Can someone provide information on the best modules/python tools to use for general database scripting? I'm interested in something that works across the board for Oracle, MySQL, MS SQL Server, and DB2. I was hoping a good generic ODBC module would be out there, but I'm having difficulty locating one that works for all. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] decimal precision in python
For money, you should probably use the builtin module 'decimal' instead: http://docs.python.org/library/decimal.html There's also the third party module 'mpmath' which provides arbitrary precision floating point arithmetic. http://mpmath.googlecode.com/svn/trunk/doc/build/index.html -Modulok- On 2/6/12, Kapil Shukla shukla.ka...@gmail.com wrote: i tried writing a small code to calculate option price using the binomial tree model. I compared my results with results of the same program in excel. There seems to be a minor difference due to decimal precision as excel is using 15 decimal precision and python (both 2.7 and 3.1) using 11. (at least that's what shown on shell) can some one guide me whats the equivalent of using a double datatype on python and i can't use long() in 3.1 any more. Please also suggest a free editor for python which can at least repeat previous command with a key stroke regards kapil ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Error Checking/Defensive Programming
It's easier to ask for forgiveness than permission. Ask yourself Is this an
action that could fail in a specific way? If yes, you need try/except. If no,
you probably need if/else. When dealing with data such as user input or opening
files and so forth, use try/except. When those actions fail, they fail in
highly specific ways. (No read/write access, no space, invalid user data, etc.)
while True:
try:
number = float(raw_input(Enter a number between 1-10: ))
except ValueError:
print(Error: You need to enter a number.)
else:
# If they got this far, we have a number of some kind.
# Check that it is in the valid range:
if number = 10 and number = 1:
# It's valid, stop the loop!
break;
else:
print(Error: Number must be in the range of 1-10.)
print(Yay, the number %.2f! % number)
On the other hand, if I was looking for an internal condition, I would use
if/else:
win_number = 3
if number == 3:
print(You won!)
else:
print(You loose!)
The rule doesn't always hold true, but it's a general guideline.
Hope that helps.
-Modulok-
On 1/25/12, Michael Lewis mjole...@gmail.com wrote:
Hi everyone,
I am new to python and have a noob question.
Is it generally better to use try/except/else statements or if/elif/else?
Or, is there a time and place for each?
For a simple example, assume I want a user to enter a number
1) try:
number = float(input('enter a number: ')
except ValueError:
print('enter a number.')
else:
print('you entered a number')
*OR*
*
*
2) number = float(input('enter a number: ')
if number =0 or 0:
print('you entered a number')
else:
print('enter a number.')
Thanks for the help.
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Re: [Tutor] Simple Question (I Hope)
On 1/14/12, Chris Kavanagh cka...@msn.com wrote:
I was looking at this code from the Python Docs
(http://docs.python.org/library/email-examples.html), trying to learn
how to send email from a Pyhton script. Anyways, part of this code
confused me. Here's the script:
1 # Import smtplib for the actual sending function
2 import smtplib
3
4 # Import the email modules we'll need
5 from email.mime.text import MIMEText
6
7 # Open a plain text file for reading. For this example, assume that
8 # the text file contains only ASCII characters.
9 fp = open(textfile, 'rb')
10 # Create a text/plain message
11 msg = MIMEText(fp.read())
12 fp.close()
13
14 # me == the sender's email address
15 # you == the recipient's email address
16 msg['Subject'] = 'The contents of %s' % textfile
17 msg['From'] = me
18 msg['To'] = you
19
20 # Send the message via our own SMTP server, but don't include the
21 # envelope header.
22 s = smtplib.SMTP('localhost')
23 s.sendmail(me, [you], msg.as_string())
24 s.quit()
What I don't understand is lines 16-18, more specifically the
msg['Subject'] format. I thought this was only done with dics??
Obviously the variable msg isn't a dic, so how can this be done??
I actually put lines 11, 16,17,18, in the interpreter, then printed out
msg, so I get what it's doing, but my question still stands. How can one
do this, when I thought it could only be done with dictionaries???
Chris,
I haven't looked at the module, but you should be aware that you can have
user-defined classes which behave like builtin types, with their own customised
features. You can also subclass a dict and customise it to do whatever. That
said, as long as an object provides dictionary access methods, it can be
treated like a dict in every respect. As far as python is concerned, if it
looks like a duck and quacks like a duck - it's a duck. (Or in this case a
dict.) It doesn't matter what the 'type' is, what is important is how you can
access it.
Here's an example::
# example.py
# The following exapmle could be done more cleanly by subclassing the builtin
# dict type, but for illustrative purposes this was not done. Instead, we show
# several dict methods being defined on our dict-like class 'Foo':
class Foo(object):
'''This object behaves like a builtin dict that refuses the value red.'''
def __init__(self, x, y):
self.x = x #-- We can have our own properties too.
self.y = y
self.data = {}
def __getitem__(self, key):
'''Return 'key' when accessed like self[key]'''
return self.data[key]
def __setitem__(self, key, value):
'''Sets self[key] = value'''
if value == red:
raise ValueError(Red is not acceptable!)
else:
self.data[key] = value
def items(self):
'''These could do whatever you want.'''
return self.data.items()
def keys(self):
'''These could do whatever you want.'''
return self.data.keys()
def values(self):
'''These could do whatever you want.'''
return self.data.values()
#===
# Now let's use it!
#===
a = Foo(x=3, y=5)
# Is 'a' a dict?
# False
print type(a)
# Is it an instance of a dict?
# False
print isinstance(a, dict)
# Can we *use* a like a dict?
a['sky'] = orange
a['ocean'] = blue
for k,v in a.items():
print k,v
for v in a.values():
print v
## Yes! Yet, it has it's own set of unique features:
print a.x #-- Prints 3
print a.y #-- Prints 5
a['blood'] = red #-- Raises exception.
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Re: [Tutor] Your thoughts on designing python code for unit testing?
In general, write the unit test *before* you write the code. This way your code is designed to be unit tested by default. It also provides a better way to verify that your implementation of a desired feature actually works as intended. For example, when I'm writing a new module I document it first. That is, I write up a bunch of code samples on how to use the module. This gives me a feel for what features I want and how I want the module to work. This is my sketch. I use the Sphinx documentation generator for this, but it could be as simple as a text document. After that I write a bunch of unit tests, which fail because there is no module written yet. Then, I write the module code to make each unit test pass, one by one. If I want a new feature I document it, write the unit test, then implement it until the unit test passes. If a feature is difficult to unit test, you probably need to re-think how you're implementing it, or re-think the interface itself. That said, this isn't always the case. With code that has to interact with many external programs, unit testing certain features can be difficult, if not impossible. Just try to get the best coverage you can. Everyone has a little different process, but that's how I do it. -Modulok- On 1/4/12, brian arb brianjames...@gmail.com wrote: What are some of the strategies for designing code to be unit tested? ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] sqlite3: turning on foreign key support thru python
How do I tell if it succeeded (short of trying an operation that should be
blocked by foreign keys)? How do I use that cursor object returned by the
pragma query to tell if its a '1' (on) or a '0' (off) and verify the state?
The cursor object contains the result set. It's a python generator object. (Or
at least a generator interface.) You have to iterate over it in order to see
the resulting rows which are stored as a tuple. Not all operations return a
result row. (For example, conn.execute('pragma foreign_keys=ON' will return a
cursor object, but it won't generate any result rows, as there were
none returned by the database.)
To see the result of your second command, do something like this::
rows = conn.execute('pragma foreign_keys')
for r in rows:
print r
You'll then see something like this when foreign keys are turned on::
(1,)
Or this when they're turned off::
(0,)
Hope that helps.
-Modulok-
On 12/16/11, Monte Milanuk memila...@gmail.com wrote:
I'm setting up an sqlite3 database to use as a base for some programming
stuff I
want to work on. Currently using python 2.7, which appears to have a new
enough
version of sqlite (just barely) to support foreign keys.
As I understand things, sqlite by default has foreign keys turned off,
unless
specifically compiled otherwise or until you turn on foreign keys using
'pragma
foreign_keys=ON'. And it needs to be turned on for each connection too.
So... just putzing around using the python interactive shell...
import sqlite3
sqlite3.sqlite_version
'3.6.21'
conn = sqlite3.connect('contacts.db')
conn.execute('pragma foreign_keys=ON')
sqlite3.Cursor object at 0x00B61860
conn.execute('pragma foreign_keys')
sqlite3.Cursor object at 0x00B6F020
It appears I am able to successfully import sqlite3, its of a recent enough
version to support foreign keys ( 3.6.19), I connected it to an existing
database 'contacts.db', and when I execute the pragma statement to turn on
foreign key support it returns a cursor object. Similarly, when I send a
pragma
statement to query the status of foreign key support, it returns a cursor
object.
Now for the stupid question(s):
How do I tell if it succeeded (short of trying an operation that should be
blocked by foreign keys)? How do I use that cursor object returned by the
pragma query to tell if its a '1' (on) or a '0' (off) and verify the state?
TIA,
Monte
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Re: [Tutor] where python is used in real world
2. If one wants to make a commercial software using python, how can he hide the code? While it's a valid question, it's fun to imagine it in the physical world: We need to permanently weld the engine compartment closed so that no one can steal our engine ideas. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] File vs. Database (possible off topic)
On 11/21/11, Ken G. beachkid...@gmail.com wrote: It occurred to me last week while reviewing the files I made in using Python, it could be somewhat similar to a database. What would be a different between a Python files and Python databases? Granted, the access in creating them are different, I really don't see any different in the format of a file and a database. Again, this may be off topic, but where can I review the basic concepts of creating a database/file. For example, when is a back up file created, after inputting a new value? Is sorting a consider a separate program after inputting a new value? It has been some 30 years since I took a course in basic data processing and I am hazy in trying to remember the basic concepts. If this is off topic, I apologized for posting here. Ken, Kentucky, USA Generally speaking, If you ever even think the word 'database', your best choice 98% of the time is sqlite. (The module is called 'sqlite3' in python.) Reading up on SQL on wikipedia and sqlite3 in the python docs is a good place to start! Eventually, if you start storing a massive number of records and need things like concurrent access and load balancing across multiple physical machines and so forth, sqlite isn't going to cut the mustard. In such cases people use a dedicated database server like postgresql, mysql, etc; A totally separate program that does nothing but database black magic. Your python programs will talk to the database server through a module written for that server. The database server will fetch, sort, update and store the actual data. Python has bindings to these heavy weight database backends through third party modules that abstract the details for you. The most popular module is probably sqlalchemy. It talks to postgresql, mysql and a few others. It's a good idea to get used to sqlite and general SQL concepts before you jump into sqlalchemy! Good luck! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] methods vs. functions
On 8/22/11, Prasad, Ramit ramit.pra...@jpmorgan.com wrote: Steven D'Aprano wrote: (Methods are very similar to functions. At the most basic level, we can pretend that a method is just a function that comes stuck to something else. Don't worry about methods for now.) Can someone please explain the difference between methods and functions? Thanks, Ramit At the most basic level, they're the same. If you have a named, stand-alone section of code that (optionally) operates on some argument passed to it, it's called a function. If you have the same exact code, but you group it together into a named unit along with the data it (optionally) operates on, it's called a method. Technically in Python, they're both objects, both callables and can be called in similar ways. The distinction is quite minimal. Here's a few examples: # A function that expects the first argument to be some object it operates on. # This is just like a method, except it hasn't been declared within any class. # Therefore, it's called a function: def setx(foo): foo.x = 1 # The same exact thing again, but declared in a 'Bar' class. Now it's # called a method. Normally the first parameter to every instance method is # named 'self', (A convention you should adhere to.) To make this example # clearer, however, I use the name 'foo' instead just like the last example: class Bar(object): def setx(foo): foo.x = 1 The call itself is a little different: # As a function you must pass the arguments: a = Bar() setx(a) #-- Explicitly pass the object as an argument. # As a method the first argument is implied: a = Bar() a.setx()#-- First argument is passed automatically for you. That said, you could also call a method as if it were a function living in the Bar namespace: a = Bar() Bar.setx(a) You can even declare a function within a class that *doesn't* operate on any instance of the class. Just like an ordinary function, you must pass all arguments. This is called a static method and is declared with the '@staticmethod' decorator: class Baz(object): @staticmethod def bonzo(x, y): return x+y You can then call it like this: Baz.bonzo(3, 5) This looks remarably similar to calling a function that exists in some namespace. For example: import random random.randrange(3, 5) So the ultimate difference? Pretty much just where you declare it. If it's in a class it's called a method, outside of a class its called a function. Especially in python - the distinction is small. -Kurt- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] floats
Can someone till me how to get a two decimal precision every time?
print %.2f % (500/1000.0)
# or...
result = 500 / 1000.0
print %.2f % result
Using 'new' style string formatting works too:
print {0:.2f}.format(500/1000.0)
-Modulok-
On 6/6/11, Michael bridges micha_el2...@yahoo.com wrote:
i saw it somewhere, but where?
i want to 10 / 1000 and get 0.01 not 0
if 1000 is made 1000.00 then 0.01 is printed
but that gives 500 / 1000.00 is 0.5 not 0.50
i might be thinking C# not python.
can someone till me how to get a two decimal precision every time?
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Re: [Tutor] Clunky Password maker
On 5/25/11, Wolf Halton wolf.hal...@gmail.com wrote:
Is there a less clunky way to do this?
[code]
def new_pass():
series = ['`', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '-',
'=', \
'~', '!', '@', '#', '$', '%', '^', '', '*', '(', ')', '_',
'+', \
'q', 'w', 'e', 'r', 't', 'y', 'u', 'i', 'o', 'p', '[', ']',
'\\', \
'Q', 'W', 'E', 'R', 'T', 'Y', 'U', 'I', 'O', 'P', '{', '}',
'|', \
'a', 's', 'd', 'f', 'g', 'h', 'j', 'k', 'l', ';', ', \
'A', 'S', 'D', 'F', 'G', 'H', 'J', 'K', 'L', ':', '', \
'z', 'x', 'c', 'v', 'b', 'n', 'm', ',', '.', '/', \
'Z', 'X', 'C', 'V', 'B', 'N', 'M', '', '', '?']
passwd = []
p = input(Enter the length you want your password to be: )
# length of password
for i in range(p):
r = random.randint(0, 94)
passwd.append(series[r]) # Append a random char from series[] to
passwd
#print passwd
#print passwd[0], passwd[1], passwd[2], passwd[3]
print
print .join(map(str, passwd)), is your new password. \n
[/code]
[output]
Enter 1 to run a MD5hash on your password
Enter 2 to run a SHA1 hash on your password
Enter 3 to run a SHA224 hash on your password
Enter 9 to get a new randomy password
Enter 10 to run away... he he he
Enter your choice here 9
Enter the length you want your password to be: 4
!bnR is your new password.
[/output]
Depending on what your passwords are going to be protecting, be aware that the
default generator in the random module is:
...completely unsuitable for cryptographic purposes.
Instead, create an instance of the 'SystemRandom' class. You also don't need to
create a list of all of your values. A simple string will do. You should also
look into the 'string' module, as it defines 'letters', 'digits' and
'punctuation' characters for you. Thus, your code be something like:
import random
import string
passlen = 10 # How long should it be?
r = random.SystemRandom()
chars = string.letters + string.digits + string.punctuation
passwd =
for i in range(passlen):
passwd += r.choice(chars)
print passwd
-Modulok-
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Re: [Tutor] Titles from a web page
You might look into the third party module, 'BeautifulSoup'. It's designed to help you interrogate markup (even poor markup), extracting nuggets of data based on various criteria. -Modulok- On 5/4/11, louis leichtnam l.leicht...@gmail.com wrote: Hello Everyone, I'm trying to write a program that looks in a webpage in find the titles of a subsection of the page: For example you have the list of the title of stories in a newspaper under the section World and you you click on it you have the entire story. I want a program that print the title only of this special section of the page. Can you help me out? I tried using regular expression but I keep hitting walls and I don't know what to do... Thank you ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to solve this problem in python?
Ratna,
This list doesn't usually do your homework. However, we will help you with key
issues. What have you tried already? Where are you stuck? Is there a certain
aspect you don't understand? (Questions like these get lots of help around
here. Informally saying do my homework generally doesn't.)
-Modulok-
On 4/24/11, Ratna Banjara mast.ra...@gmail.com wrote:
Write a function named countRepresentations that returns the number
of ways that an amount of money in rupees can be represented as rupee
notes. For this problem we only use rupee notes in denominations of
1, 2, 5, 10 and 20 rupee notes.
The signature of the function is:
def countRepresentations(int numRupees)
For example, countRepresentations(12) should return 15 because 12
rupees can be represented in the following 15 ways.
1. 12 one rupee notes
2. 1 two rupee note plus 10 one rupee notes
3. 2 two rupee notes plus 8 one rupee notes
4. 3 two rupee notes plus 6 one rupee notes
5. 4 two rupee notes plus 4 one rupee notes
6. 5 two rupee notes plus 2 one rupee notes
7. 6 two rupee notes
8. 1 five rupee note plus 7 one rupee notes
9. 1 five rupee note, 1 two rupee note and 5 one rupee notes
10. 1 five rupee note, 2 two rupee notes and 3 one rupee notes
11. 1 five rupee note, 3 two notes and 1 one rupee note
12. 2 five rupee notes and 2 one rupee notes
13. 2 five rupee notes and 1 two rupee note
14. 1 ten rupee note and 2 one rupee notes
15. 1 ten rupee note and 1 two rupee note
Hint: Use a nested loop that looks like this. Please fill in the
blanks intelligently, i.e. minimize the number of times that the if
statement is executed.
for (int rupee20=0; rupee20=__; rupee20++)
for (int rupee10=0; rupee10=__; rupee10++)
for (int rupee5=0; rupee5=__; rupee5++)
for (int rupee2=0; rupee2=__; rupee2++)
for (int rupee1=0; rupee1=__; rupee1++)
{
if (___)
count++
}
--
Regards,
Ratna P Banjara
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Re: [Tutor] Metaclass confusion...
Peter, ... the class, i. e. the instance of the metaclass with all its attributes has already been created by the type.__new__() method. If you move the manipulation of the members dict into a custom __new__() method you get the desired behaviour... Thank you! You've solved my problem and broadened my understanding :) Excellent examples as well. Love the class name too. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Metaclass confusion...
List, I've been messing with metaclasses. I thought I understood them until I ran into this. (See code below.) I was expecting the generated class, 'Foo' to have an 'x' class-level attribute, as forced upon it by the metaclass 'DracoMeta' at creation. Unfortunately, it doesn't and I don't know why. I'm obviously missing something big. I thought a metaclass created the class object, so this should work. (But obviously doesn't.) !-- Begin Code -- class DracoMeta(type): '''Metaclass that creates a serial number as a class property.''' def __init__(self, name, bases, members): # Force a class attribute on the class-to-be: members['serial'] = 3 # Now make the class: type.__init__(self, name, bases, members) class Foo(object): __metaclass__ = DracoMeta print hasattr(Foo, 'serial')#-- I was really expecting this to be True. !-- End Code -- I could add the attribute in the definition or a decorator, but the point was learning to use (albeit abuse) metaclasses. Anyway, if anyone could take a look I'd be grateful. Thanks! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] String formatting question.
For simple strings I use the %s % foo version, for more complex stuff I use
the .format() method. I find it easier to control spacing and alignments with
the .format() method, but that's just me.
-Modulok-
On 3/29/11, Blockheads Oi Oi breamore...@yahoo.co.uk wrote:
On 29/03/2011 20:41, Prasad, Ramit wrote:
Is there a difference (or preference) between using the following?
%s %d % (var,num)
VERSUS
{0} {1}.format(var,num)
Ramit
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From Python 2.7.1 docs at
http://docs.python.org/tutorial/inputoutput.html Since str.format() is
quite new, a lot of Python code still uses the % operator. However,
because this old style of formatting will eventually be removed from the
language, str.format() should generally be used..
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Re: [Tutor] time taken to execute certain task
On 3/16/11, tee chwee liong tc...@hotmail.com wrote: hi, i would like to know the time taken to execute a certain task in python. i used time.time and time.clock and i see the time taken is different? what is the right method to use? import time def testtime(num): start=time.time() #print start for n in range(num): #print n print time.time()-start testtime(101) start = time.clock() for x in range(101): y = x # do something end = time.clock() print Time clock elapsed = , end - start, seconds thanks tcl Also look into the builtin module 'timeit' if you're trying to benchmark things. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Shared web host and setting the python environment...
List, Background: I'm on a linux based shared web host. They cater to PHP, not python. (There's no third party python modules even installed!) So I installed a virtual python in my home directory, plus easy_install and a bunch of modules. Great! The Problem: Unfortunately, the web server uses the system python, not my virtual python, or my modules. (It does execute my scripts as my uid though.) I need modify the environment of every one of my python scripts, perhaps appending to sys.path, so that my third party modules in my home directory can be found. I have zero control over the web server process or its environment. Possible Solutions I thought of: One way to do this would be to edit 'sys.path' at the top of every python script. (Sounds ugly.) Another would be to import the 'user' module and go that route. (Fine, but it's depricated. What replaces it?) A third idea would be to re-direct all requests via mod_rewrite to a single python file or shell script, which sets the environment and calls my python scripts as a sub-process. (Slow, which is fine, but some security concerns here.) Given my situation, what's the best way to accomplish this? (Aside from a new hosting company or a virtual private server.) Any suggestions appreciated. Thanks! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Help - want to display a number with two decimal places
On 3/4/11, lea-par...@bigpond.com lea-par...@bigpond.com wrote:
Hello
I have created the following code but would like the program to include two
decimal places in the amounts displayed to the user. How can I add this?
My code:
# Ask user to enter purchase price
purchasePrice = input ('Enter purchase amount and then press the enter key
$')
# Tax rates
stateTaxRate = 0.04
countrySalesTaxRate = 0.02
# Process taxes for purchase price
stateSalesTax = purchasePrice * stateTaxRate
countrySalesTax = purchasePrice * countrySalesTaxRate
# Process total of taxes
totalSalesTax = stateSalesTax + countrySalesTax
# Process total sale price
totalSalePrice = totalSalesTax + purchasePrice
# Display the data
print '%-18s %9d' % ('Purchase Price',purchasePrice)
print '%-18s %9d' % ('State Sales Tax',astateSalesTax)
print '%-18s %9d' % ('Country Sales Tax',countrySalesTax)
print '%-18s %9d' % ('Total Sales tax',totalSalesTax)
print '%-18s %9d' % ('Total Sale Price',totalSalePrice)
Lea,
Notice that 'd' in your string substitution means integers, not
floats. Any decimal places will be truncated when using 'd'. For
floats use 'f' instead. You an also specify a precision, such as
'%.2f' shows two decimal places.
However, to make all of your numbers line up nicely, regardless of how
long they are, you need to look into advanced string formatting via
the builtin string method 'format()'. It takes a little practice to
understand and use, but the results are exactly what you want.
(See: http://docs.python.org/library/stdtypes.html#str.format)
Here's an example you could put at the bottom of your code to see it in action:
print {0:18} {1:18.2f}.format(Country Sales Tax, countrySalesTax)
print {0:18} {1:18.2f}.format(Purchase Price, purchasePrice)
# First prints the first argument (the 0th index) to 'format(),
# left aligned '', and 18 characters wide, whitespace padded.
# Then prints the second argument, (the 1st index) right aligned,
# also 18 characters wide, but the second argument is specified to
# be a float 'f', that has a precision of 2 decimal places, '.2'.
-Modulok-
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Re: [Tutor] File transfer HTTP - SFTP
This isn't a python solution, but if you have an ssh connection to both servers, (I assume so) you can forward them directly. It would look like this in an operating system shell like tcsh or bash: me@baz scp -r m...@foo.com:/home/me/pictures m...@bar.com:/somewhere/ You could wrap the above command with python via the subprocess module if needed. -Modulok- On 3/1/11, Emanuel Lauria emanuel.lau...@gmail.com wrote: Sorry if im annoying, but I think this is a better question than my previous one of today. I have some Images in an HTTP Server that I need to transfer to an SFTP server using a Python script. So far I can download them to my hard drive, and upload them to the sftp server; quite easy. I would like to do the transfer without touching my hard drive. How could I do that? Im using paramiko, but STPClient.put() reads from the filesystem. Thanks put(self, localpath, remotepath, callback=None) Copy a local file (localpath) to the SFTP server as remotepath. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Generator expressions...
List,
I was messing around with generator expressions. I tried to make a
script that would read a few bytes from '/dev/urandom' for eternity.
It then did something pointless like computing checksums and printing
them out. Unfortunately, the script only runs a few seconds and then
terminates. I'm not sure why. I tried running it on /dev/zero as well
with the same result; The process terminates, albeit normally. (Exit
status 0. It's not being killed by the kernel or anything.) I was
expecting it to run forever. Below is my code:
## Begin code
#!/usr/bin/env python
# This script will only work on UNIX flavors with a /dev/urandom
#
# It reads from /dev/urandom for eternity, or until you press 'ctrl+c' to
# interrupt it. It computes the hashes forever.
# The point being illustrated is that its memory usage is about constant,
# despite an infinitely large file being read.
import hashlib
fd = open('/dev/urandom', 'rb')
gen = (hashlib.sha256(i).hexdigest() for i in fd.read(4096))
try:
for i in gen:
print i #-- This loop should never end... but does. Why?
except KeyboardInterrupt:
gen.close()
fd.close()
print \nBye!
## End code
I've got to be missing something obvious.
-Modulok-
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Re: [Tutor] Generator expressions...
import hashlib
fd = open('/dev/urandom', 'rb')
gen = (hashlib.sha256(i).hexdigest() for i in fd.read(4096))
try:
for i in gen:
print i #-- This loop should never end... but does. Why?
except KeyboardInterrupt:
gen.close()
fd.close()
print \nBye!
Check out the generator expression. What are you iterating over? How
long is the string returned by the read?
I knew it was subtle. I was trying to use 'read(4096)' like open()'s
buffersize parameter. (Which it's obviously isn't.)
Thanks!
-Modulok-
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Re: [Tutor] accessing another system's environment
I'm coming into this thread late so I might be off the mark here, but it seems like you're going about it backwards: Instead of trying to reach in and modify a user's environment, which is highly variable and process dependent, why not just wrap the software they're running? Have a python script wrap all of the programs you're trying to configure on the client's machine. (No matter how you do it, you'd have to install a client program of some kind anyway.) When they launch the 'program' in question, they're really launching a python script. The script checks in with a remote server that holds the config files or environment data. (Or whatever else you need.) The client script says some thing like I'm john, running program version x.x. Give me my env variables.) The server then replies with any variables that the client needs to set and their values. You could do this with a python script running on a server sending ajax responses. (There's an ajax module in the standard library.) The wrapper, running on the client gets the response and set any environment variables for the process it's about to launch. It then starts the real program, passing the properly configured environment on to it. You have to write two programs. 1. A client wrapper that asks the server for its data and 2. A simple server that passes any data back to the client. In effect, you'll be able to change the clients configuration, environment variables or *anything else* that needs done before your script launches the the real client program. You don't have to deal with screwing around with the client's environment or the complexities that brings up either. On 2/26/11, Dave Angel da...@ieee.org wrote: On 01/-10/-28163 02:59 PM, Steve Willoughby wrote: On 26-Feb-11 01:19, ALAN GAULD wrote: Bill, That's the same thing we are talking about. The problem is those environment variables are highly variable so you can't talk about a machine's environment. Two users on the same machine (at the same time) may have very different environments. And a batch file or program can I'm a Unix hacker, so forgive me if my understanding of Windows is a bit naive. I think, though, that Windows has a set of environment variables which are system-wide, added automatically to the user set of variables when a new process is launched. Yes, they can be changed or deleted but there is a standard set applied to all users. If that's a correct assumption on my part, there must be somewhere that can be read from, probably (I would guess) in the registry. So a script which could read/write those registry keys may do what is required here. The issue of exposing that to remote machines remains a dangling issue, though. Of course, it's not entirely clear we're solving a Python question, although this discussion may well go more solidly into that space. Indeed. in Windows, there are two sets of registry keys for environment variables, one is system wide, and one is per user. When Explorer launches a console or an application for a particular user, it combines those two sets of keys to come up with an initial set of environment variables. I tried to launch a VirtualBox XP machine, but it failed for some reason. Probably I have too much else running. So I can't tell you the key names. I'd suggest asking about remotely accessing the registry on the python-win32 forum. I'm sure the win32 extension have a way, I just don't know if it'll work from a Linux client. DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] accessing another system's environment
On 2/26/11, Modulok modu...@gmail.com wrote: ... The server then replies with any variables that the client needs to set and their values. You could do this with a python script running on a server sending ajax responses. (There's an ajax module in the standard library.) ... Sorry, I meant a 'json' module, not 'ajax'. I've been doing too much web programming recently :p. You could probably even get away with not having to write a server, just set up a web server to handle it, sending a well-formed response. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Try except really better than if?
On 1/9/11, Karim karim.liat...@free.fr wrote: Hello all, I am using more and more try except statement. But I discussed with a very experienced C++ programmer. And he told me that at least in C++ using too many try -catch statements are making the code slower. And it should does the same for python (C implementation). My simple question: Is this true? And why using try-except is indeed encouraged to code as a pythonista? Regards Karim Exceptions are almost always slower to catch. You can confirm this via the 'timeit' module in the standard library. However, if the performance of exceptions themselves become significant, there are bigger, more fundamental problems with your code. Python isn't a language chosen for execution speed. Python is chosen for ease of use and readability. If you find you have to sacrifice that for your project, you might look into a faster language, but not before trying a few things (which solves the problem 99% of the time): 1. Test it. Don't guess. Actually benchmark your code. (See the timeit module.) Is it fast enough? If you have a cron job that runs once every minute that turns over a few log files, having it run in 0.026 seconds is no better than having one that runs in 0.015. 2. Find where the bottleneck is. Again use timeit, and start to look at our iterative algorithms. Better algorithms can speed up some code significantly. (But again, only if you must!) Ask for help on this list, see if there's a module written by someone that does what you want, or research various algorithms that fit your purpose yourself. 3. Still not fast enough? Implement those speed-critical pieces of your code in C and call them from Python. This should be rarely needed. 4. Still not fast enough? You either didn't do step 1 or screwed up between step 2 and 3, or you need more hardware. A try...except...finally block is a lot easier to read, and more flexible than an if...elif block, for catching specific exceptions. Even if your code was twice as slow with exceptions, but your code still runs 'fast enough' for whatever purpose you've written it for, then it's fast enough. Don't obfuscate it. That said, don't use exceptions so liberally that you no longer worry about checking for good inputs. If something usually succeeds just go for it and use an exception as accident insurance. If it will usually fail, check it with an if statement first. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Weighted Random Choice - Anyone have an efficient algorithm?
Does anyone know of an efficient way of doing a weighted random choice? (I don't even know what algorithms like this would be called.) Preferably, something that doesn't grow exponentially with the number of elements in the list, or the size of their respective values. For example: Assume I have a list of integer elements. I want to pick an index from that list, using the value of said elements to control the probability of selecting a given index: w = [5, 20, 75] wrand(w) Where wrand() will return '2', (the index of 75), about 75% of the time. It would return '1', (the index of 20) about 20% of the time, and 0, about 5% of the time. It could return the actual value, but returning the index seems more flexible. The implementation doesn't have to work exactly like this, even if the weight values don't add up to 100, or are arbitrary, that's fine. Hopefully you get the idea. Here's what I tried (it works, but is slow): ### Begin Code Example ### import random random.seed(2) #-- So we can reproduce the sequence for testing. def wrandom(weights): ''' Return a randomly selected index of the 'weights' list, using the values of that list to affect probability of said index being returned. ''' debug = False flattened = [] for i, w in enumerate(weights): if debug: print i, w: , i, w for k in range(w): flattened.append(i) if debug: print flattened: , flattened rnd = random.randint(0, (len(flattened) - 1)) return flattened[rnd] # Not test it: print wrandom([5, 20, 75]) print wrandom([5, 20, 75]) print wrandom([5, 20, 75]) ### End Code Example ### It works and is easy enough to understand, but when the number of list items gets large, or the weights get heavy, things get ugly. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] unit testing - Separate methods or group tests together?
List, When you create unit tests, do you group tests for a given function together into one unit test method, or do you prefer to have separate test methods for every assert statement? Thanks! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Writing to the terminal?
List, Thanks! I think I got it working now with the help of some suggestions :-) For more complex stuff, (think blue screens with little white boxes you press spacebar to activate. Kind of like an OS installer) I would look into the `curses` module in the standard library? Thanks! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Writing to the terminal?
List, Forgive me if I don't describe this well, I'm new to it: Assume I'm working in a command shell on a terminal. Something like tcsh on xterm, for example. I have a program which does *something*. Let's say it counts down from 10. How do I print a value, and then erase that value, replacing it with another value? Say I had something like '10' that appears, then wait a second, then the 10 is replaced by '9'... '8'.. and so forth. The point is, I don't want to print to a new line, nor do I want the new number to appear next to the previous number... I just want to change it in place. (If that makes any sense?) Think of console based progress counters in programs like fetch or wget, or lame. How do you do this in Python? -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Calling Program within Program
Patty, I didn't read through your code, but to call an external program see the 'subprocess' module in the standard library: http://docs.python.org/library/subprocess.html -Modulok- On 12/9/10, pa...@cruzio.com pa...@cruzio.com wrote: Hello: I would like to know how to call a program from within a program and what directory I should place one small program file in. I am running Python 2.6.6 and Windows 7. I have a directory called C:\Users\StarShip\PyProgs and it has the files BreakersCafe.txt and BreakersCafe.py. This is my primary program running fine. I have a subdirectory called C:\Users\StarShip\PyProg \PicturesForTesting and another subdirectory C:\Users\StarShip\PyProgs\CustomFunctions with various program files, functions defined in them, etc. which I import in my primary program. For example: def Newbanner(): print \n Alternate Selections\n Now I have the small program below which is fully self-contained and I want to execute it from within BreakersCafe.txt. I would like to use raw_input and if statement for simple yes/no asking if they would like to see this BeveragesMenu.txt and have it as the last 3-4 lines of the main(). The only directory of these three that has __init__ is C:\Users\StarShip\PyProgs\CustomFunctions and as you can see, the program below is not a function, it has no 'def' anything. I get 'NameError: global name 'BeveragesMenu' is not defined' when I run this in IDLE. I suppose I _could_ make this a function :} but it is likely doable to call a program as a program, right? I am also compiling to a .pyw file where applicable. Thanks for the help. Patty This is C:\Users\StarShip\PyProgs\BeveragesMenu.txt and BeveragesMenu.py. Program file for displaying an image using Tkinter built-in GUI functions. open root window, open file descriptor for image, open new window file descriptor to manipulate with Tkinter Label library function. Pic needs to be displayed as a banner. Uses the compound=top argument to do this. -- take out the pack()function didn't work, pack()is required Uses import Tkinter Program using new breaker's jpg picture; bar choices are not selectable import Tkinter import ImageTk rootwindow = Tkinter.Tk() fhdl= ImageTk.Image.open(C:\Users\StarShip\PyProgs\PicturesForTesting\houseimage.jpg) image_var = ImageTk.PhotoImage(fhdl) whdl = Tkinter.Label(rootwindow, compound=top, image=image_var, text=\n\n!!!WELCOME TO BREAKER'S BREAKFAST BAR!!!\n\n\nBeverage Choices: Sparkling Water; Milk; Orange Juice; Apple Juice *OR*\n\n **From Our Bar**Smoothie; Breakers Sun Tea; Chai; Cafe Mocha; Latte; Mimosa) whdl.pack() rootwindow.mainloop() ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] True Random Numbers
On 11/2/10, Crallion cralli...@gmail.com wrote: In an attempt to generate true random numbers, I found this python script- http://code.google.com/p/truerandom/ Getting to the point, I get this error when I run my program. File /dev/python/absolute/truerandom.py, line 9, in module from urllib import urlopen ImportError: cannot import name urlopen Is urllib and/or urlopen deprecated in 3.1.2 or is it something I forgot to do? Python is running on OSX 10.6, which I upgraded from the default install to 3.1.2. The only 'true' source of entropy is a hardware random number generator. For cryptographic work you don't need this. All you need is a seemingly endless unpredictable sequence of bits. For this purpose, a cryptographically secure pseudo random number generator will do nicely. Furthermore, if your intent was for encryption, you shouldn't be getting your entropy over the wire for obvious reasons. (Speed and security.) With your stress on 'true' random numbers, I can only assume your intent is encryption. That said, use the operating system's random number generator. This will vary from system to system in how it is implemented, but all systems have one which is suitable for cryptographic purposes. On *NIX flavors this will be /dev/random. You can either read from this file directly to get a random stream of bits, or use the python standard library to interface with it to do things like get random numbers (as others have pointed out.) Whether reads to this, or calls which use this, will block, waiting for a suitable amount of entropy, depends on the system your code runs on. For example on FreeBSD both '/dev/random' and '/dev/urandom' are always non-blocking. FreeBSD uses a crypto secure 256-bit pseudo random number generator based on yarrow. The same is true for Mac OS X and AIX. On linux '/dev/random' will block if the entropy pool is exhausted, while '/dev/urandom' will not, but is still considered cryptographically secure. (And far better than any home brewed solution.) Also remember, 'pseudo-random' doesn't mean 'almost random,' it means deterministic *if you know the initial state*. (This is only true of some generators though, as some perturb their state with external sources of entropy on a regular basis.) On python you can get random numbers through the operating system's '/dev/urandom' (or on Windows, CryptGenRandom ): # Python example of getting secure, random numbers using the standard library: # This works in python 2.4 and greater on most systems: import random foo = random.SystemRandom() # Uses /dev/urandom or Windows CryptGenRandom # Print 10 random numbers: for i in range(10): foo.random() What are you using the random numbers for? -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] unittest testing order...
List, When using the unittest module, tests are run in alphanumeric order. What's the suggested way of specifying a test order? Any code examples would be great! Thanks -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] unittest testing order...
On 9/27/10, Steven D'Aprano st...@pearwood.info wrote: On Tue, 28 Sep 2010 04:03:17 am Modulok wrote: List, When using the unittest module, tests are run in alphanumeric order. What's the suggested way of specifying a test order? There isn't one. It shouldn't matter what order the tests run, no test should *rely* on another test. (Although of course, if one test fails, any tests which assume the missing functionality will also fail.) In an ideal world, I agree. This is possible for pure functional programming where state is avoided. However, when dealing with object oriented, imperative programming, state changes cannot be avoided. Thus if a method requires an object be passed to it, I'd like to verify that object is being constructed correctly by the object factory, before verifying that the method which uses said object, is correct. Or is there some other way of doing this? I'm new to unittesting. Thanks! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] quick speed question
This is faster:
if dict['key'] == 'foo':
pass
...But just slightly. (About 9% faster on my machine. This may differ
depending on the implementation, but I doubt it. See the 'timeit'
module.) Whether it's a big deal depends on what you're doing.
Accessing the dict - a million times - with either method took less
than a second. Visually, this makes more sense to me:
if dict['key'] == 'foo':
pass
Regardless, you should be aware that while they look similar, they
differ in their semantics:
# Something to work with:
dic = {'a': Big, 'b': Bigger}
# This is true:
if dic['a'] == Big:
print True
# And this is true:
if Big in dic['a']:
print True
# But this is also true!
if Big in dic['b']:
print True
As far as speed is concerned: Don't worry about it unless has already
become a problem. Premature optimization wastes time you should be
spending solving the actual problem. For example, if you wrote an MP3
player that sorted playlists in 0.1 seconds instead of 0.2
seconds (100% faster!), but you wasted 3 days doing it - you haven't
accomplished much.
When you're done and you find you need a faster solution, optimize
your algorithms. If that still isn't enough, ask somebody smarter than
yourself to look at it. (This list is great for that!) If that too
fails, start think about writing a few critical bits in C, but only as
a last resort.
We should forget about small efficiencies, say about 97% of the time:
premature optimization is the root of all evil -Donald knuth-
-Modulok-
On 9/16/10, C.T. Matsumoto c.t.matsum...@gmail.com wrote:
Hello Tutors,
I was just wondering if you have a dictionary key is it faster to do:
if dict['key'] == 'foo':
...
or is this faster:
if 'foo' in dict['key']:
...
Or is there any difference and I'm chasing ghosts?
Thanks,
T
--
C.T. Matsumoto
Claes de Vrieselaan 60a III
3021 JR Rotterdam
The Netherlands
tel.: +31 (0)6 41 45 08 54
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Re: [Tutor] Advice on math
Hello, I've enjoying learning python for the first few years, and appreciate all the help I have received from this list. I had some interest in programming and am very glad to have made python my choice of programming language. Since I didn't go to college for computer studies, I feel my math is kind of rusty in some areas, and looks like improving/regaining math skills would help a lot in programming, logic, algorithms, etc. Right now I think I need a better understanding of logarithm, arrays (matrixes), and even probability. What links would you all recommend that would be useful for me to learn these things in a newbie-friendly way? If you want to code+learn, nothing beats ProjectEuler ( http://projecteuler.net/ ). However I assume you have basic understanding of maths. Not to hijack the thread, but that's awesome! Only when you solve the problems and then read the forum thread, do you realize how crude your own solutions are, compared to some very clever fellows. Far better than a crossword to keep things stimulated. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Data exchange formats...
List, What's the best format to send data across the wire between processes? I have some simple 'insensitive' data I need to send from a client, to a server via a TCP socket. Things like 'count = 10, name=foo' and so forth. Basic values. I would use something like the 'pickle' module to pack them up send as encoded strings, which would then be loaded on the server. It'd be nice, but the server has no authentication. Therefore: Warning The pickle module is not intended to be secure against erroneous or maliciously constructed data. Never unpickle data received from an untrusted or unauthenticated source. Currently I'm sending strings and using regular expressions on the server to pluck out the needed data, but thought there must be something cleaner, nicer and better. Ideas? ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] help
Solution: width times height. On 6/17/10, KB SU k24...@gmail.com wrote: help ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Trouble with sockets...
List,
I'm new to sockets and having trouble. I tried to write a simple
client/server program (see code below). The client would send a string
to the server. The server would echo that back to the client.
PROBLEM:
I can send data to the server, and get data back, but only for the
first call to the 'sendall()' method. If I try to call it in a loop on
the client, to print a count-down, only the first call gets echoed.
Clearly, I'm missing something.
EXAMPLE: (They're on the same physical machine.)
Shell on the server:
modu...@modunix ./socket_server.py
Listening for clients...
Got connection from 192.168.1.1
Shell on the client:
modu...@modunix ./latency_client.py 192.168.1.1 2554
0
What I wanted:
[-]modu...@modunix ./latency_client.py 192.168.1.1 2554
0
1
2
CODE:
# The client program:
import socket
import sys
def main():
'''Send data to a server and receive the data echoed back to us.'''
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect( ('192.168.1.1', 2554) )
for i in range(3):
s.sendall(str(i))
print s.recv(1024)
s.close()
# Execution starts here:
try:
main()
except KeyboardInterrupt:
sys.exit(Aborting.)
# The server program:
import socket
import sys
def main():
'''Listen for a client and echo data back to them.'''
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind( ('192.168.1.1', 2554) )
s.listen(5)
print Listening for clients...
while True:
channel, client = s.accept()
print Got connection from %s % client[0]
message = channel.recv(1024)
channel.send(message)
channel.close()
# Execution starts here:
try:
main()
except KeyboardInterrupt:
sys.exit(Aborting.)
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Re: [Tutor] Making pretty web pages from python code examples?
: Basically, I'm trying to read python code examples from files on : disk and generate pretty little web pages from them. I think you may want sphinx [0] which is available in PyPI [1]. It understands reStrucTured text and adds a few Sphinx-specific directives/features for pulling the docstrings from your python modules. Much easier than building your own. Thanks! Looks like just what I'm after. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Making pretty web pages from python code examples?
Is there an easy way to get a docstring from a python file, without first importing it? Basically, I'm trying to read python code examples from files on disk and generate pretty little web pages from them. I invision the docstring appearing as the main text on the page, with the rest of the code in HTML code or pre tags. That way I could just write up a bunch of python samples, without having to do anything more but upload them. Maybe something like this exists already? I don't know. I just figured it would be pretty easy to write, but getting the docstrings without trying to parse the files was a rut. Thanks. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Introduction to modelling with Python
Could you further define 'modeling' in context? Are you referring to using python in the context of 3D modeling, i.e. computer aided design? If that be the case, python serves as an embedded language for many 3D computer graphics programs. Everything from Maya to Houdini use it as a command interface to automate things. See the developer's documentation for whatever software you're using. What kind of modeling? -Modulok- On 3/27/10, AG computing.acco...@googlemail.com wrote: Hi List I apologise in advance for the vagueness of this query, but I am looking for a decent modern introduction to modelling using Python. Specifically, I want something that is a good introduction (i.e. doesn't expect one to already be a maths/ statistics or a programming guru) and that has an ecology/ environmental science orientation. The latter is desirable but not essential, as I suspect that once one understands the process of data abstraction and the other steps involved in modelling processes and scenarios, the thinking and skill sets are likely transferable. However, if my assumption about this is incorrect, please let me know. If anyone knows of any resource (book or on-line) with a Python bent, please let me know. I am preparing to begin applications to Ph.D. programs and most of what I am interested in doing requires some knowledge of modelling and Python also seems to be widely accepted as a programming language, so I am happy with that as I am in the process of teaching myself Python anyway. Thanks for any help, advice, etc. Cheers AG ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Bowing out
After six years of tutor posts my interest and energy have waned and I'm ready to move on to something new. I'm planning to stop reading and contributing to the list. I have handed over list moderation duties to Alan Gauld and Wesley Chun. Thanks to everyone who contributes questions and answers. I learned a lot from my participation here. Kent, I'm a relative newcomer, but even so, I benefited from you. Thanks for giving what you could! Best of luck with your new endeavors. Hope to see you check back in from time to time. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Encryption
I need a simple way to encrypt and decrypt some strings with a key. Did you have any other requirements? Any specific algorithms or key lengths? If you need real encryption, you might check out a 3rd party module named 'PyCrypto'. It offers an implementation of the AES algorithm. A less eloquent approach - you could also wrap the Unix command 'openssl' with a python process. Whether you can get these libraries will depend on where you live. Strong encryption is still strictly controlled in some regions. There are code examples in the 'README' file of pycrypto. There are probably other AES implementations out there as well. However, the only FIPS certified library I know of is openssl. -Modulok- On 2/22/10, Shashwat Anand anand.shash...@gmail.com wrote: how about using base64? base64.encodestring(s) will do. On Tue, Feb 23, 2010 at 2:30 AM, Wayne Werner waynejwer...@gmail.comwrote: On Mon, Feb 22, 2010 at 2:50 PM, Antonio Buzzelli anto.buzze...@gmail.com wrote: Hi everyone! I need a simple way to encrypt and decrypt some strings with a key someone can help me?? I'm sure someone can. -Wayne ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] adding more text to a file
If you're using this as an interactive command to help you populate a
database, as you appear to be, don't open the file more than once. As
previously suggested you should also put all your strings together and
then write them to the database in one go.
I don't know if you've thought about this yet, but you'll need a way
to stop when you're done inputing names and ages! Here are two
thoughts you can look into: 1) Check for a special character (or lack
thereof). For example, if the fields are blank you could exit the loop
using the 'break' statement. Or 2) Catching a 'KeyboardInterrupt'
exception using the 'try...except' statements. Without doing it for
you, (I assume this is homework) these are some suggested changes:
out_file = open('persons.txt', 'w')
while True:
name = raw_input(What is the name: )
age = raw_input(What is the age: )
out_file.write(name:%s\nage: %s\n\n (name, age))
# We'll never get this far unless we figure out a way to stop the loop!
out_file.close()
Keep at it and best of luck!
-Modulok-
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[Tutor] How to create memory backed file?
List,
How do I create a file which exists only in memory? (Think diskless.)
I need to create an in-memory file. I need to pass this file, as a
regular file object, to a subprocess. Unfortunately, the 'mmap'
module's file-like object doesn't appear to work quite like a regular
file would. (I simply assume that mmap would be the way to go. Other
suggestions welcome!) That, or I'm doing something terribly wrong. For
example:
import mmap
import sys
from subprocess import Popen, PIPE
fishes = one fish\ntwo fish\nred fish\nblue fish\n
###
# With a real file, this works:
###
fd = open('fish.txt', 'w')
fd.write(fishes)
fd = open('fish.txt', 'r')
proc1 = Popen(['cat'], stdin=fd, stdout=sys.stdout, stderr=sys.stderr)
###
# This doesn't (with mmap file):
###
vfd = mmap.mmap(-1, len(fishes), mmap.MAP_PRIVATE)
vfd.write(fishes)
vfd.seek(0)
proc2 = Popen(['cat'], stdin=vfd.fileno(), stdout=sys.stdout, stderr=sys.stderr)
I just get the following error:
Traceback (most recent call last):
File stdin, line 1, in module
AttributeError: fileno
I'm using Python 2.5, so I cannot use that slick
'SpooledTemporaryFile' method of the 'tempfile' module. The 'cat' is
just a simple Unix system command for the purpose of illustration.
Thanks!
-Modulok-
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Re: [Tutor] How to create memory backed file?
Kent, Thanks! I think that'll do it. I don't know what this list would do without you! -Modulok- On 12/27/09, Kent Johnson ken...@tds.net wrote: On Sun, Dec 27, 2009 at 3:36 AM, Modulok modu...@gmail.com wrote: List, How do I create a file which exists only in memory? (Think diskless.) I need to create an in-memory file. I need to pass this file, as a regular file object, to a subprocess. Unfortunately, the 'mmap' module's file-like object doesn't appear to work quite like a regular file would. (I simply assume that mmap would be the way to go. Other suggestions welcome!) That, or I'm doing something terribly wrong. How about using a pipe for stdin? This seems to work: import sys from subprocess import Popen, PIPE fishes = one fish\ntwo fish\nred fish\nblue fish\n proc1 = Popen(['cat'], stdin=PIPE, stdout=sys.stdout, stderr=sys.stderr) proc1.stdin.write(fishes) proc1.stdin.close() Kent ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] More on unit testing - tests for external data...
So, this, 'test environment', this is just like a directory where I place my code and associated files to test for the existence (and non-existence) of various stuff, right? Any real-world examples/case studies to point to? It seems like there are a lot of people on this list interested in getting more familiar with unit testing, but not a whole lot of non-trivial, python-specific examples being passed around. I can write a function in a programming 101 class that accepts two arguments and returns a value by computing the hypotenuse of a triangle (or whatever). I can then build a unit-test for that making sure it fails and passes as needed. Cake. But jump into the real-world where many things are not so trivial, and I'm at a loss for where this unit-testing business all fits in. Basically, I'm trying to become a better programmer. (Who isn't?) I'd like to transition from 'hacky but gets the job done' or 'oh my God it actually works' to 'eloquent and bulletproof'. Without some kind of a mentor or vast array of tutorials to lay down the law when I screw up, or pass on some kind of approval when I get something right - it's been frustrating as hell. Case studies/tutorials anyone? Thanks! -Modulok- On 12/10/09, spir denis.s...@free.fr wrote: Wayne Werner waynejwer...@gmail.com dixit: On Wed, Dec 9, 2009 at 6:15 PM, Alan Gauld alan.ga...@btinternet.comwrote: Remember, in testing you are not trying to prove it works but rather to demonstrate that it doesn't! So in that way it's a bit like the the scientific method (or exactly like)? You create a hypothesis and design tests to invalidate your hypothesis... and if they fail to invalidate you may have a valid hypothesis. Simply replace hypothesis with program and you get the testing procedure? -Wayne programming is modelizing -- like a scientist's job Denis la vita e estrany http://spir.wikidot.com/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] More on unit testing - tests for external data...
List, Unit testing functions and methods which rely on passed data is simple enough. However: How do I unit test something which relies on external data? For example, a function which creates a file only if it doesn't exist on disk, or a unit test for a function which makes an SQL query? If anyone could point to a few examples of such usage, that would be great! Thanks! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] python time
Doesn't time.time return a float? import time help(time.time) Help on built-in function time in module time: time(...) time() - floating point number Return the current time in seconds since the Epoch. Fractions of a second may be present if the system clock provides them. time.time() 1259288538.576565 Right? -Modulok- For sure, but this wasn't my question. I was precisely asking how python does that. Clearly I have a mighty need to consume more coffee. My apologies for misreading the original post. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] python time
Doesn't time.time return a float? import time help(time.time) Help on built-in function time in module time: time(...) time() - floating point number Return the current time in seconds since the Epoch. Fractions of a second may be present if the system clock provides them. time.time() 1259288538.576565 Right? -Modulok- On 11/26/09, Kent Johnson ken...@tds.net wrote: On Wed, Nov 25, 2009 at 11:11 AM, spir denis.s...@free.fr wrote: Hello, How does python get the time in microseconds? (In other words, how would I get it if python (like some other languages) would provide time in whole seconds only?) Use the source...in particular, see floattime() in timemodule.c: http://svn.python.org/view/python/branches/release31-maint/Modules/timemodule.c?view=markup Kent ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Fwd: Help on finding the 1000th prime
Also watch things like letter case on stuff like 'Print' and 'While', they should instead be 'print' and 'while', (all lowercase). -Modulok- On 11/16/09, bob gailer bgai...@gmail.com wrote: Here is the code that doesn't work. Thanks for posting the code. What doesn't work mean? error messages? unexpected results? or what? There are several problems in your code. - The candidates you are testing. Walk thru the program and list a few of them and see if you can determine that problem. - Counting primes as you discover them. Same advice as above. - indentation is screwed up. Please use only spaces - no tabs. primeCount = 0 primeCandidate = 2 While primeCount = 1000: isPrime = True primeCandidate = primeCandidate + 2 for x in range(2, primeCandidate): if primeCandidate % x == 0: print primeCandidate, equals, x, *, primeCandidate/x isPrime = False Print primeCandidate break If isPrime: primeCount = primeCount + 2 Print primeCandidate -- Bob Gailer Chapel Hill NC 919-636-4239 ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] OT: Writing code while tired, counterproductive?
List, This is kind off topic, but: Does anyone else find, writing code while tired to be counterproductive? It just seems like when I push myself to stay up late finishing a project, I sorely regret it the following day. Granted, Python is a fairly forgiving language and doesn't take the mental attention that some others require (like C++ ...or someone else's C++ or someone else's poorly written C++), but for me, writing code while tired usually ends up being a bad thing - In any language. But then there's the guilt of taking the day off and not meeting deadlines. *grumble* Just wondering if this is a common occurrence among the masses. Anyone? -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to call a method with a print statement?
List, __repr__() is exactly what I was looking for :) You guys rock! Thank you. -Modulok- On 11/12/09, Dave Angel da...@ieee.org wrote: Kent Johnson wrote: On Thu, Nov 12, 2009 at 6:35 AM, Luke Paireepinart rabidpoob...@gmail.com wrote: On Thu, Nov 12, 2009 at 5:29 AM, Jeff R. Allen j...@nella.org wrote: You are looking for the __str__ method. See http://docs.python.org/reference/datamodel.html#object.__str__ Can't you also implement __repr__? Yes, in fact if you are only going to implement one of __str__ and __repr__, arguably __repr__ is a better choice. __repr__() is called by the interactive interpreter when it displays an object. __str__ is called by print, and if you don't define __str__ it will call __repr__. So defining only __str__ will not give a custom representation unless you print: In [1]: class Foo(): ...: def __str__(self): ...: return I'm a Foo In [2]: f = Foo() In [3]: f Out[3]: __main__.Foo instance at 0x1433468 In [4]: print f I'm a Foo Defining __repr__ will give the custom representation when you just give the name of the object: In [5]: class Foo2(): ...: def __repr__(self): ...: return I'm a Foo2 ...: ...: In [6]: f2=Foo2() In [7]: f2 Out[7]: I'm a Foo2 In [8]: print f2 I'm a Foo2 Kent And one other important place that uses __repr__() is the printing of containers. So if you have a list of Foo2 objects, and you want to just say print mylist it's better to have __repr__(). ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] How to call a method with a print statement?
List, How do I get a print statement to call a class method? I'm using python 2.5. I did it long ago, but can't remember how, or even where I learned it from. Something like: class Foo(): def __init__(self): pass def ***part I can't remember goes here*** print hello world! # Now use it: bar = Foo() print bar hello world! #-- Magic! If any of this makes sense, any pointers would be great! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Evaluating a string expression
[snip] I would like to know how would I evaluate a string expression in python. For example, if i say: a = 3*2 I want to do something to evaluate the variable 'a' to give me 6. How can I do this? [/snip] The eval() function can do this: eval(3*2) WARNING: Long winded security rant below... Be *very* careful what strings you pass to eval(). It is executing code! If you're doing this in a controlled environment it's not a problem. If this is part of a bigger program which is going to be used by other people, perhaps even online, this is a potentially *huge* security risk. You will either have to very carefully parse the users input to control what they can and cannot do, or better, strictly control what the kernel permits the process to do. This includes what hardware resources (memory/processor time) the process is allowed. This way, even if (when) the process is hijacked, the damage will be very limited. Such a feat is accomplished by having the program execute as a user who has very limited permissions. This is something best (only?) done on UNIX/Linux/BSD flavored systems. This could be done via a setuid binary, or a *carefully written* root process which immediately demotes its privilege level upon execution/spawning of children. (Such a model is employed by programs like apache's httpd server, where one process is root owned and does nothing but spawn lesser privileged processes to handle untrusted data.) If this is something you're interested in, the os module features functions like, 'setuid()', 'setgid()', and notably 'chroot()'. For further security yet, you might look into isolating a process from the rest of the system, as is the case with FreeBSD's jails. These are really big topics and in the end, it really depends on what 'untrusted source' constitutes, and your operating environment. Writing bulletproof code in regards to security is challenging. It is a very specialized topic worthy of further study. But in most situations executing code from an untrusted source is a *really* bad idea, even with precautions as those outlined in the example URL provided by one of the other responses. (http://effbot.org/zone/librarybook-core-eval.htm) Sorry for all the lecture. I'll shut up now. :p -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] why is os.path.walk so slow?
[snip] I need to synchronize the files on my home and office machine and have been using someone else's code for this to date but have been frustrated by how slow it is in getting the information on files for the mounted drive from my office machine... [/snip] Not to cut your coding project short, and it may not even be applicable, but have you looked into rsync? They kind of wrote the book on efficiency in regards to synchronization of files. Just a thought. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Stolen thread: Bottom folk vs. toppers was trouble using 2to3.py
[snip] The war between bottom posters and top posters has been long, arduous, and most often incredibly silly. There have been written group rules mandating one over the other. Oft times these rules have doomed the group. Two words come to mind: Bikeshed color. I simply propose that the only requirement to communications here is that replies and questions be well formulated, courteous, and reasonably intelligent. Yup. -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Generating unique ID
I'm writing an application which will hold a database of people. Ofcourse, people can have the same name, so I want to stock them with an unique ID. I've searched and found some things: - uuid.uuid4() - id(name) - os.urandom(n) But they seem overkill to me. Well, maybe not id(). What should I use the best for this? Maybe examples of other programs that do something alike? Use the auto-increment feature of your database database management backend. (Assuming you're using a database backend like MySQL, postgresql, etc.) In MySQL your database description would look something like this (with any other fields you need): # MySQL table description: CREATE TABLE IF NOT EXISTS mytable ( `uid`BIGINT unsigned NOT NULL auto_increment unique, `uname` CHAR(32) NOT NULL default guest, PRIMARY KEY (`uid`)); You could use MySQLdb (third party python module) to talk to the MySQL process with Python. Other database managers have similar abilities. os.urandom(n) Random numbers are random, NOT unique. If you're using your own backend, like a text file or whatever, stop. Take the time to learn to use a database manager like postgresql or MySQL or whatever. They have already solved many of the problems you're now facing. It will be well worth the time and frustration. Otherwise, you'll have to parse your database and get the previously used value and then increment that. However, this solution will fail if there are multiple processes, or threads accessing the data concurrently. To solve that problem you'll have to introduce some manner of mutex to gurantee that only one process has access to the unique data at any given time. Things get complicated. All of these problems have already been solved with other database managers. Use them! In a pinch, with a low volume database for non-critical data, you could probably get away with using a Unix epoch style timestamp with sufficient granularity. But even this is in no way, guaranteed to be unique. It's just, probably unique. It would look like this: import time time.time() 1256796357.661967 If it absolutely must be unique, use a database manager that can make that guarantee. Best of luck! -Modulok- ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to load a dict into a dict subclass?
snip
...
Assume I have a dict, 'foo'. I also have my own class, 'Bar', which
subclasses (i.e. is a derived class) of a dict. How do I eloquently
get foo into an instace of Bar? Example:
### BEGIN CODE:
class Bar(dict):
pass # Act like a dict for now.
foo = {'a': 100, 'b': 200, 'c': 300} # This could be a function return
value.
myvar = Bar()
# The hacky feeling part:
for k,v in foo.items(): myvar[k] = v
### END CODE
You can use the built-in function for dictionaries called update. So
class Bar(dict):
pass
foo = {'a':100, 'b':200, 'c': 300}
myvar = Bar()
myvar.update(foo)
myvar
{'a': 100, 'c': 300, 'b': 200}
...
/snip
Thanks guys!
Christian, that's just what I was looking for. Thank you!
-Modulok-
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[Tutor] How to load a dict into a dict subclass?
List,
I'm new to the list, (somewhat new to python too). My code feels
hacky. I'd like to know if there is a more eloquent way (more below).
If not, a general thumbs up from more experienced programmers would be
great!
Assume I have a dict, 'foo'. I also have my own class, 'Bar', which
subclasses (i.e. is a derived class) of a dict. How do I eloquently
get foo into an instace of Bar? Example:
### BEGIN CODE:
class Bar(dict):
pass # Act like a dict for now.
foo = {'a': 100, 'b': 200, 'c': 300} # This could be a function return value.
myvar = Bar()
# The hacky feeling part:
for k,v in foo.items(): myvar[k] = v
### END CODE
Obviously I can put the dict into an instance variable, but then
methods like 'keys()' and such won't work. If that makes any sense...
Thanks guys!
-Modulok-
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