[Tutor] replacement for constants from other languages in Python?

Thu, 06 Jan 2005 00:16:33 -0800 

Hey all,

I've done the usual googling, checked the Learning Python book and did some list searches, to no avail as of yet.

I'm _very_ used to using C style constants (preprocessor #define directives) or C++ const keyword style, for a variety of reasons.

I've yet to see anything covering 'how to work around the lack of constants in Python'...can anyone point me in the right direction here?

A few examples/reasons for use:

The 'need' to define a global constant in an imported module, for example- (I know about sys.version_info, but it doesn't exist in 1.5.2...don't ask ;-) I also know this could be handled via a class, but what is the equivalent of the following snippets? Not so interested in style comments (I am, but not on these/this thread ;-) as much as other ways to do this..

1.
ourversion.py:

import sys

MINVERSION = 1.5

def checkVersion():
        """ used as an evil hack because 1.5.2 doesn't have                     
 
        sys.version_info
        """

        # Not sure why, but declaring MINVERSION as repr(foo) in the
        # first place doesn't work, something about python type handling
        # I'm sure..
        return repr(MINVERSION) >= repr(getVersion())

def getVersion():
        return sys.version[0:3]

if repr(getVersion() < 2.0)
        # boo, we have no builtin bool
        global True
        global False
        True = 1
        False = 0

funkyScopeAndConstants.py:
import ourversion.py
import sys
import os
import <someOtherModule>

...
...
if someOtherModule.property = True
        # do something

You get the point.

The other oddity is without being able to define a 'real' constant, as in #DEFINE MINVERSION 1.5,

the scope of MINVERSION (and True/False) even using the global keyword still uses the ocal file's namespace. I don't want to debate the merits of using globals...most people that claim they never use any in other languages _still_ use constants in header files, which is the purpose I'd like to be able to do generally....not to mention the fact that I really am _not_ thrilled with the use of string literals typed in each time in code (yes, quick and dirty code but still) I see seems to be 'OK' in python for the use of comparisons...opposed to something like

if(strncmp(strVal,
        CONSTANT_STRING_VAL_LIKE_HTTP_ACCEPT_ENCODING_HEADER,
        strlen(strVal)
        {
                do_something();
        }

or
if(floatVal > PI)
{
        do_something()
}

ok, hopefully that's explaining some of why I'd like a 'constant equivalent' as well as a question on global scoping/python namespaces.

A last question would also be if the equivalent of __FILE__ and __LINE__ macros exist?

Thanks,

Scott

        
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