Mimic C preprocessor with Python/Ruby?

I need to mimic the preprocessor feature of C with Python.

If I want to run the debug release, I use as follows with C

#ifdef DEBUG
printf(...)
#endif

I just use -DDEBUG or similar开发者_开发问答 to trigger it on or off.

What method can I use for Python/Ruby? I mean, what should I do to control the behavior of python/ruby scripts in such a way that I can change a variable that affects all the script files in a project?

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You usually use the python logging functionality in this use-case. That is configured in configuration files, and you can set the output levels. Very close in usage to java log4j, if you're familiar with that.

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You can almost use the actual C preprocessor. If you rename your file to end in .c, you can then do this: gcc -w -E input/file.py.c -o output/file.py.

The main issue seems to be with comments. The preprocessor will complains about python comment lines being invalid preprocessor directives. You can remedy this by using C++ comments (// comment).

Or, a better idea would be to just write your own simple preprocessor. If you only need #define functionality, you're just talking about a doing a search and replace on your file.

Another solution would be something like this:

def nothing(*args):
    pass

def print_debug(msg):
    print msg

if not DEBUG: 
    print_debug = nothing

That way your print statements don't do anything if you're not in debug mode.

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Use pypreprocessor

The latest release can also be accessed through the PYPI

Here's the basic usage:

from pypreprocessor import pypreprocessor

pypreprocessor.parse()

#define debug

#ifdef debug
print('The source is in debug mode')
#else
print('The source is not in debug mode')
#endif

There you go. C style preprocessor conditional compilation implemented in python.

SideNote: The module is compatible with both python2x and python3k.

Disclaimer: I'm the author of pypreprocessor.