I'm writing Python as if it were strongly typed, never recycling a
name to hold a type other than the original type.
Is this good software engineering practice, or am I missing something
Pythonic?
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I assembled a good conventions set for Java. View it at
http://www.martinrinehart.com/articles/code-conventions.html (is that
better, Steve?)
It followed a logical organization; it was built from four other
extensive (if not well-organized) convention sets and it scrupulously
avoided injecting my
Daniel Fetchinson wrote:
I'm sorry to disappoint you but this project has already been completed:
http://www.python.org/dev/peps/pep-0008/
Daniel, PEP 8 is anything but complete. How much of the following
simple question can you answer from there:
Given that you can name things with
Thanks, all.
Good to know no one's been beheaded.
Yes to separating test and non-test code, but no if that will just
turn one modest module into two modules, smaller still.
Amen to 'practicality beats purity.'
Do wish we had a good, thorough convention set. I wrote one for Java.
It took a lot
By convention, I've read, your module begins with its import
statements. Is this always sensible?
I put imports that are needed for testing in the test code at the end
of the module. If only a bit of the module has a visual interface, why
pollute the global namespace with 'from Tkinter import *'?
Writing Tkinter menu code used to be rather tedious, uninspiring work.
I figured that I could delegate the job to a program:
http://www.martinrinehart.com/articles/menus.py
Run it. Then look at the source (bottom of file). There's a bit more
doc in the doc comment at the top.
Peer review is
Is there a way of translating from the Text widget's width/height (in
characters) to pixels so you can open an appropriately sized window?
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Guilherme Polo wrote:
there is a
gui designer tool for tkinter called GUI Designer (what a bad name),
which used to be called SpecTcl, where you can design the menus and it
then converts to python code.
I tried it. after about 10 minutes I was as far as help not found.
Is anyone out there
[EMAIL PROTECTED] wrote:
menudef =
File
New,callNew,Ctrl-N
New Window, callNewWindow, Ctrl-Shift-N
__
Open, lambda e=0:para(1), Ctrl-O
Nice design. I looked at it for a few seconds and didn't even
think about pressing F1.
Mine does less.
Tkinter defaults to, for example, Alt+f = File (if File is your first
menu name starting with f).
I'd like to assign my own letters and have them underscored, per the
universal standard. Can this be done?
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Guilherme Polo wrote:
Set the underline option to the index of the desired letter
Elegant simplicity in the dropdowns. Thanks!
Now, how about main menu underscores?
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Eric Brunel wrote:
BTW, this standard is not universal at all: e.g, there is no such
convention on Macs.
Thanks for the info. It's standard on Windows and Linux/KDE. GNOME,
anyone?
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What are the considerations in choosing between:
return [a, b, c]
and
return (a, b, c) # or return a, b, c
Why is the immutable form the default?
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(Accompanied by Marvin Gaye)
def f(list=[0]):
...list[0]+=1
...return list[0]
...
f()
1
f()
2
f() # 'list' is a name bound to a list (mutable) so this makes sense
3
f([5])
6
f() # What's Going On?
4
Off topic: Motown chief Berry Gordy tells Gaye he won't release the
uncommercial
Jeroen Ruigrok van der Werven wrote:
http://www.martinrinehart.com/articles/python-grammar.html:
Unknown host www.martinrinehart.com
Works for me.
Very interesting. The link I posted works for me, while the links
quoted are 404 errors, though they look identical. This really is a
superior
I previously posted a link to an improved, HTML-based, hyperlinked
grammar.txt. Discard that one. This one is much better.
http://www.martinrinehart.com/articles/python-grammar.html
If you find it useful, thank Gabriel Genellina for encouraging me to
get it really right.
It includes three
Why is the preferred delimiter for multi-line strings?
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D'Arcy J.M. Cain wrote:
Where did you see that? The only place I saw it was the style guide
and it was only talking about docstrings.
PEP 8 and 257, and you're right, they are both about docstrings.
Also, I'd never seen an example of the triple apostrophe form until I
dove
into the formal
[EMAIL PROTECTED] wrote:
It includes three corrections to grammar.txt (imagnumber, xor_expr and
and_expr) that I've reported.
Make that four corrections. Add augop.
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Gabriel Genellina wrote:
About the generated page: I think it would be more useful if each symbol
links to its definition, instead of showing an alert(). This way it's
easier to navigate the tree, specially with complex declarations.
That was my first shot. It didn't work. (Every line is its
Gabriel and Steve,
Poor globals! They take such a beating and they really don't deserve
it.
The use of globals was deprecated, if memory serves, during the
structured design craze. Using globals is now considered bad practice,
but it's considered bad practice for reasons that don't stand close
Steve Holden wrote:
I wish you'd stop trying to defend this code and simply admit that it's
just a throwaway program to which no real significance should be
attached. *Then* I'll leave you alone ;-)
You're hurting my program's feelings!
Actually, I intend to keep this program as the nice
Paul McGuire wrote:
plus sundry other parts of the kitchen
sink) that was passed BY PROJECT CODING STANDARDS to EVERY FUNCTION IN
EVERY MODULE! Supposedly, this was done to cure access problems to a
global data structure.
Beautiful example of how totally stupid actions can be taken in the
Thanks so much Gabriel.
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Implemented all your suggestions, with two exceptions.
Changed file read to readlines(), but not open(...).readlines(). I
love to say file.close(). Gives me a feeling of security. (We could
discuss RAM waste v. I/O speed but this input file is just 10KB, so
neither matters.)
Removed one of the
I spent too long Googling for Python's BNF. Eventually found it at
Python.org, but only by accident.
I've put Python's BNF here:
http://www.martinrinehart.com/articles/python-parse-bnf.html
Extensively cross-referenced.
Addenda:
No, Google, I didn't want the Botswana daily news with its
My parser has found an expression of the form CONSTANT_INTEGER
OPERATOR CONSTANT_INTEGER. I want to fold this into a single
CONSTANT_INTEGER.
The OPERATOR token has an intValue attribute, '+' == 0, '-'== 1, etc.
In C I'd put functions Add, Subtract, ... into an array and call
ArithmeticFunctions[
Simon Forman wrote:
yes! check out http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/464635
HTH,
~Simon
Thanks, Simon. Looks like that will do it.
Actually, it looks like that will overdo it. I'll be setting File/Save
to enabled after every keystroke. Ideally, I'd like to set my
re encryption
I ran a small software company in the '80s. We did the unthinkable:
shipped our software with a money-back guarantee. Anyone could buy the
software, copy it and then request a full refund.
Return rate: 0.5%. Of the returns we guessed that about half of them
were for perfectly legit
I have a simple editor built into my visual parser. It has a File menu
with
typical New, Open, Save, Save As ... options. I now know how to set
the options [en/dis]abled and how to check the Text widget's modified
flag.
Now I want to [en/dis]able those options. Can I ask the text to notify
me
A fascinating, well-informed discussion. Thanks to all.
Holden's suggestion re coupling and cohesion was most informative. I
conclude that whether you use an object or a global (within a module,
not across modules) is an implementation detail that has no impact on
either cohesion or coupling.
Rob Wolfe wrote:
But I think that you should read this:
http://effbot.org/zone/vroom.htm
Rob, may the gods shower you with gold coins!
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re being serious
I am serious. I am seriously trying to develop a nice language for
beginners. I was at Dartmouth in 1965 when BASIC was new. It let me
use the computer without learning Fortran. It was very successful. I
think it's past time for another one. I think we could have a lot more
I had a global variable holding a count. One source Google found
suggested that I wouldn't need the global if I used an object. So I
created a Singleton class that now holds the former global as an
instance attribute. Bye, bye, global.
But later I thought about it. I cannot see a single advantage
Jeff Schwab wrote:
What's the Intel architecture? Do you mean the x86_64 architecture
that was actually developed by AMD, or x86 for x some number, or do
you actually mean IA64?
I mean chips of the family that goes back to the 8086 and 8088 chips,
chips that support the REPZ prefix to the
Paul Rubin wrote:
repz movsw is a pretty lame way to copy data on current x86's.
Use XMM instead.
Thank you, Paul. I'm pretty sure you meant MMX, Multi-Media
eXtensions.
Paul's just told me to upgrade my 32-bit thinking to use newer 64-bit
registers, even on a 32-bit cpu. Please divide my
Steve Holden wrote:
You have a strange idea of nearly free ...
Extending an integer array from 100 to 150 items is a pretty puny
operation when you compare it with the amount of data that might need to
be moved during a compactifying garbage collection of a 20MB Python
program image.
20
Gabriel Genellina wrote:
I don't like Tk because the widgets are ugly, old-fashioned, and don't
have the right look and feel.
Take another look. A year or so back Tkinter went to platform native
widgets.
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[EMAIL PROTECTED] wrote:
IOW: all this is assumed to be
common *n*x knowledge.
Both GNOME and KDE put Windows to shame. An old Windows guy, like me,
can just start using either one without needing 'common *n*x
knowledge.' Too bad the *n*x community isn't more welcoming to
outsiders.
Paul Boddie wrote:
Here's one page which probably tells you stuff you already know:
http://wiki.python.org/moin/BeginnersGuide/Download
Thank you! It says I need Python (which I've got) and the Python-devel
package, which sounds like it might include Tkinter and IDLE. Now if
only I knew
Many thanks to all.
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Paul Rubin wrote:
The problem here is with a high allocation rate, you have to GC a lot
more often, which typically involves copying live data.
This is last century's issue. Copying data, RAM to RAM, is nearly free
using the Intel architecture.
This short article,
Paul Boddie wrote:
The whole CNR stuff and the
proprietary software slant of Linspire obscures the solution, in my
opinion.
Thanks for all your help, Paul.
CNR, which is now free, is absolutely marvelous when it's got what you
need. If Python2.5 were in the warehouse, I'd have clicked, gone
I went to Python.org, DL'd Python 2.5 source code per the usual
inadequate instructions and ran the make files successfully (sort of).
Python 2.5 works fine. But from Tkinter import * gets a What's
Tkinter? message. IDLE's no where to be found.
What's not in the instructions is what directory
Everything I've read about Tkinter says you create your window and
then call its mainloop() method. But that's not really true. This is
enough to launch a default window from the console:
from Tkinter import *
foo = Tk()
Google's great, but it has no truth meter. Do I inherit from Frame? Or
is
Tkinter gets no respect. But IDLE's a Tkinter-based app and every
example I've Googled up shows Tkinter as needing about half as much
code as wx to do the same job. I'm beginning to Tkinter up my language
application. Am I making a big mistake?
--
I researched this for some Java I wrote. Try to avoid shuffling
physical memory - you'll write a lot less code and it will be faster,
too.
Use an allocated list and an available list. Keep them in address
order. Inserting (moving list elements from insertion point to end)
and deleting
Diez B. Roggisch wrote:
No, there is no way. You would change general interpreter behavior if
you could set arbitrary operators for predefined types.
Start grumping...
Thank you, Diez.
If I ever design a language, please remind me that complete, easy,
well-documented access to the working
If it were my choice, the plus sign would do this:
def itemadd( i1, i2 ):
if ( type(i1) == str ) or ( type(i2) == str ):
return str(i1) + str(i2)
else:
return i1 + i2
I'd like to redefine it so it works my way but operator overloading
seems strictly confined to classes I
Hexamorph wrote:
You mean you want the ability to change for example the + operator
for ints to something like calculating the cosine instead of doing
addition?
Sure. Cosines are a monadic operation and the monadic '+' is a NOP, so
why shouldn't I define +45 to return cosine of 45,
I'm ready to start coding the parser for my Decaf (beginners)
language. I think that a visual parser (one that shows what it's
doing as it does it) would be nice. (And I think that it would help
the parser author by saving the requirement for a bazillion print
statements while debugging the tool.)
Matthew Woodcraft wrote:
I think [the olpc guidlines are] mostly PEP 8, with some notes added.
Took a good look. You are absolutely correct.
PEP 8 is basically word processing text stuck between pre and /pre
tags. OLPC is Wiki HTML. Good example of how the latter is a lot
bigger than the
Thanks to all for many helpful suggestions.
Python, by the way, is verbose when compared to APL. (See
http://catpad.net/michael/apl/ if you don't believe this.) You need to
stick in an adverb (maybe gracefully concise) as standalone
concise is owned by APL.
Basilisk96 wrote:
Did programmers
That's a great list, grflanagan! Thanks.
I looked at each and copied to my disk either as a .txt (cut/paste
from the browser) for a page or less or as .html (view source, chop
off head and non-guideline stuff, save). This is the list plus PEP 8
minus the software. (No disrespect for the software,
I'm a Java guy who's been doing Python for a month now and I'm
convinced that
1) a multi-paradigm language is inherently better than a mono-paradigm
language
2) Python writes like a talented figure skater skates.
Would you Python old-timers try to agree on a word or two that
completes:
The
There's a lot of dumb stuff out there. Algorithms should be coded
efficiently ... Thanks, I'll keep that in mind.
van Rossum's guidelines tend toward pick something and stick to it
which is OK if you have enough experience to pick something Pythonic.
I'm a relative newbie, not qualified to pick.
From the manual:
code objects are immutable and contain no references (directly or
indirectly) to mutable objects (3.2)
I thought my code worked with both mutable and immutable objects.
Whassup?
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Thank you both.
Stupid me, went to Python.org and found Style Guidelines and thought
that was the last word. Oh well.
PEP 8 reminds me a lot of Sun's Java conventions, in ways I wish it
didn't. The overall structure seems like a random list of topics and
it omits a lot. For Java I went from Sun
Guilherme Polo wrote:
foo = [
'too long',
'too long too',
...
]
OK, I'll put it there too, and it will be easy for us to read each
other's code (at least in this particular).
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Jeroen Ruigrok van der Werven wrote:
I got someone who asked me to make changes in an old Fortran program she is
using for some calculations.
Why convert? Modern Fortran is an object oriented, structured language
with the singular advantage that it can run old Fortran programs.
--
Working on parser for my language, I see that all classes (Token,
Production, Statement, ...) have one thing in common. They all
maintain start and stop positions in the source text. So it seems
logical to have them all inherit from a base class that defines those,
but this doesn't work:
import
Jeroen Ruigrok van der Werven wrote:
Shouldn't this be:
self.startLoc = start
self.stopLoc = stop
Thanks! Of course it should. Old Java habits die slowly.
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Dennis Lee Bieber wrote:
Great if one is using a teletype as editor
The original Dartmouth computer room was a basement that featured 8
teletypes.
The original BASIC, Dennis, was implemented on a time-shared
mainframe with a gigantic 8k words (20-bit words, if I remember) of
core memory.
Bruno Desthuilliers wrote:
[EMAIL PROTECTED] a �crit :
Bruno Desthuilliers wrote:
... that's definitively not
something I'd store in global.
So where would you put it?
You don't have to put functions arguments anywhere - they're already
local vars.
Bruno, right now I've got
Hendrik van Rooyen wrote:
I wonder if you have some COBOL data divisions under your belt?
Hendrik, I go way back but somehow I missed COBOL.
Martin
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Bruno Desthuilliers wrote:
... that's definitively not
something I'd store in global.
So where would you put it?
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Chris Mellon wrote:
You don't seem to be implementing the
lexer in Python
I am absolutely implementing my language in Python, a language I have
now been writing for two entire weeks. This list has been more than
helpful, tolerating numerous newbie questions.
--
Steven D'Aprano wrote:
Context is all gone, so I'm not sure that I remember what it is. I
think it is the text that you're parsing.
Yes. I'm tokenizing today. Parsing comes after Christmas.
TEXT = placeholder
def parse():
while True:
token = get_next_token() # looks at
Tokenizer accepts 0x as zero. Spec says its an error not to have at
least one hex digit after 0x.
This is a more serious bug than I had originally thought. Consider
this:
Joe types security_code = 0x and then goes off to the Guardian-of-
the-Codes to get the appropriate hex string. Returning to
Sion Arrowsmith wrote:
Michael Sparks [EMAIL PROTECTED] wrote:
def bar():
global x
x[0] += another
print id(x[0])
... and for bonus marks, explain why the global x in this function
is not required.
Because x does not appear as an LHS in bar(), just about the first
thing I
If I get to add multi-line strings today, I'll have a complete
tokenizer. Interior looks a lot like C minus semi-colons. (Though I
did figure out that there wasn't any need for tokens that didn't come
from a real to have a doubleValue field. In C++ or Java all the Tokens
had a doubleValue, because
Tokenizer bug reported.
[EMAIL PROTECTED] wrote:
int('0x', 16)
0
I'm working on a tokenizer and I'm thinking about returning a
MALFORMED_NUMBER token (1.2E, .5E+)
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Duncan Booth wrote:
Why would you return a token rather than throwing an exception?
Tokenizers have lots of uses. Colorizing text in an editor, for
example. We've got a MALFORMED_NUMBER when you type '0x'. We've got an
INTEGER when we get your next keystroke (probably).
--
John Machin wrote:
Use a proper lexer written by somebody who knows what they are doing,
as has already been recommended to you.
My lexer returns a MALFORMED_NUMBER token on '0x' or '0x '. Try that
in Python.
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Gabriel Genellina wrote:
Do you have to validate input based on that grammar?
I've built a standalone tokenizer. It returns an array of Token
objects. These include tokens such as UNCLOSED_QUOTE and
MALFORMED_NUMBER ('1E' not followed by sign or digit, for instance).
You could use this in a
Chris Mellon wrote:
Is there some reason that you think Python is incapable of
implementing lexers that do this, just because Python lexer accepts
it?
Absolutely not. My opinion is that it's a bug. A very, very minor bug,
but still six-legged.
Note that if you're using your lexer to mark
Thinking about unclosed multi-line quotes.
When you open a multi-line quote (type '') what does your editor
do? Does it color the remainder of your text as a quote, or does it
color the line with the open quote as a quote and leave the rest of
your code alone?
What do you want it to do?
This is
Hi, Bruno. Merry Christmas!
By constant I meant that it did not change during the lifetime of
the Toker.
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Is the following correct?
x = some string
x is a reference to some string
foo(x)
Reference is passed to function.
In foo:
x += change
Strings are immutable, so x in foo() now points to a different string
than x outside foo().
Right?
Back outside foo.
x = [some string]
x is a
... the first element of the list to which x refers is a reference to
the new string and back outside foo, the first element of the list to
which x refers will be a reference to the new string.
Right?
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int('0x', 16)
0
I'm working on a tokenizer and I'm thinking about returning a
MALFORMED_NUMBER token (1.2E, .5E+)
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My 2 cents.
Eurozone? That would be 3 cents US.
I meant colon, not semi-colon. I did the tutorial. I did objects 3
times.
In Java, the agreed convention is to use lowerAndUpper naming for
member variables. (See
http://www.MartinRinehart.com/articles/code-conventions.html#5_1
.)
10 days is
This morning block comments disappeared from the Decaf design. Maybe
later today they'll be instantiated in the tokenizer.
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I've got a pointer to a position in a line of code that contains
either a digit or a period (decimal point). I've got this comment:
Numbers are one of these:
integers:
digit+
0xhex_digit+
decimals:
Fortran (1957) had line comments. C (1972) replaced these with non-
nested block comments. C++ (1983) added here-to-EOL comments. Python
(1991) keeps here-to-EOL comments but replaces block comments with
multi-line quotes. Block comments and multi-line quotes both serve the
same purpose as doc
Sion Arrowsmith wrote:
Given a one-or-the-other choice, any editor worth using can do
comment/uncomment region, and if only to-EOL comments are
available, it will do that for you instead of using block
comments. So block comments are not really a useful language
feature.
I'd expect the
Warning! Complaints coming.
The good news is that 10-days of part-time Python coding has convinced
me that I picked the right language. Now, observations.
First, it is absolutely horrible being a newbie. I'd forgot how bad it
was. In addition to making a fool of yourself in public, you have to
My 2 cents...
Thanks for the feedback, Bruno. Seriously thinking about ditching the
block comments and adding multi-line strings. (Block comments are the
last item on my tokenizer's todo list. Multi-line strings would be
easier.)
Beginners will be programming fun things in a GUI environment.
I've designed a language, Decaf, for beginners. I've got block
comments but not multi-line strings.
If you can only have one or the other, which is more helpful?
Should I have both? (Make a strong argument here: my design principal
is, Designed by a backpacker: when in doubt, leave it out.)
--
Jonathan Garnder said:
Well, if using something like PLY ( http://www.dabeaz.com/ply/ ) is
considered more Pythonic than writing your own parser and lexer...
Lex is very crude. I've found that it takes about half a day to
organize your token definitions and another half day to write a
Most unclear. My apologies.
I'm trying to structure a tokenizer. The stupid concatenations are
just placeholders for the actual tokenizing work. By rebuilding the
input they demonstrate that the framework correctly processes all the
input.
I'm currently using a C-style design (my own pointers
Bruno Desthuilliers wrote:
Then the first move is to carefully eval existing solutions:
http://wiki.python.org/moin/LanguageParsing
Always good advice, Bruno. How did you come by that list address?
Google or is there something special known to Python experts?
--
Thanks to a lot of help, I've got the outer framework for my tokenizer
down to this:
for line_number, line in enumerate(text):
output = ''
for char_number, char in enumerate(line):
output += char
print 'At ' + str(line_number) + ', '+ str(char_number) +
I don't understand what I don't understand in the following:
--
# reader.py - testing char-by-char marching methods
f = open('sample_decaf.d', 'r')
text = f.readlines()
f.close()
# this is C-style, 15 lines, in Python:
end_line = len(text)
line_ptr = 0
Thanks to all!
I will put my class defs first (tho not without expressing my
disappointment that this is required in a late 20th century language);
learn about enumerate as it looks like exactly what I need and discard
my C++/Java based object model because this is a totally other thing.
If
confused.
Martin
Peter Otten wrote:
MartinRinehart wrote:
However, here's the little tester I wrote:
# t.py - testing
global g
g = 'global var, here'
def f():
print g
f()
It prints 'global var, here,' not an error message. Wassup?
Try it again
Tomorrow is block comment day. I want them to nest. I think the reason
that they don't routinely nest is that it's a lot of trouble to code.
Two questions:
1) Given a start and end location (line position and char index) in an
array of lines of text, how do you Pythonly extract the whole block
re top posting
Thanks for explaining. google groups hides the quoted text, so I
didn't see it.
Bruno Desthuilliers wrote:
[EMAIL PROTECTED] a �crit :
OT
Martin, would you _please_ learn to quote properly ? top-posting and
keeping the whole text of the previous posts are two really annoying
Bruno Desthuilliers wrote:
Is the array of lines the appropriate data structure here ?
I've done tokenizers both as an array of lines and as a long string.
The former has seemed easier when the language treats EOL as a
statement separator.
re not letting literal strings in code terminate
Bruno,
Please explain why the NOP import is a GoodThing. Use small words
please. I'm not as young as I used to be.
I didn't know about reload(), but now that I'm informed on that point
I'm still using
os.remove('foo.pyc')
reload(foo)
A single command to do that would be nice.
Martin
Bruno
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