Importing a long list of constants to a Python file

In Python, is there an analogue of the C preprocessor statement such as?:

#define MY_CONSTANT 50

Also, I have a large list of constants I'd like to import to several classes. Is there an analogue of declaring the constants as a long sequence of statements like the above in a .py file and importing it to another .py file?

Edit.

The file Constants.py reads:

#!/usr/bin/env python
# encoding: utf-8
"""
Constants.py
"""

MY_CONSTANT_ONE = 50
MY_CONSTANT_TWO = 51

And myExample.py reads:

#!/usr/bin/env python
# encoding: utf-8
"""
myExample.py
"""

import sys
import os

import Constants

class myExample:
    def __init__(self):
        self.someValueOne = Constants.MY_CONSTANT_ONE + 1
        self.someValueTwo = Constants.MY_CONSTANT_TWO + 1

if __name__ == '__main__':
    x = MyClass()

Edit.

From the compiler,

NameError: "global name 'MY_CONSTANT_ONE' is not defined"

function init in myExample at line 13 self.someValueOne = Constants.MY_CONSTANT_ONE + 1 copy output Program exited with code #1 after 0.06 seconds.

Python isn't preprocessed. You can just create a file myconstants.py:

MY_CONSTANT = 50

And importing them will just work:

import myconstants
print myconstants.MY_CONSTANT * 2

Python doesn't have a preprocessor, nor does it have constants in the sense that they can't be changed - you can always change (nearly, you can emulate constant object properties, but doing this for the sake of constant-ness is rarely done and not considered useful) everything. When defining a constant, we define a name that's upper-case-with-underscores and call it a day - "We're all consenting adults here", no sane man would change a constant. Unless of course he has very good reasons and knows exactly what he's doing, in which case you can't (and propably shouldn't) stop him either way.

But of course you can define a module-level name with a value and use it in another module. This isn't specific to constants or anything, read up on the module system.

# a.py
MY_CONSTANT = ...

# b.py
import a
print a.MY_CONSTANT

And ofcourse you can do:

# a.py
MY_CONSTANT = ...

# b.py
from a import *
print MY_CONSTANT

Sure, you can put your constants into a separate module. For example:

const.py:

A = 12
B = 'abc'
C = 1.2

main.py:

import const

print const.A, const.B, const.C

Note that as declared above, A, B and C are variables, i.e. can be changed at run time.

As an alternative to using the import approach described in several answers, have a look a the configparser module.

The ConfigParser class implements a basic configuration file parser language which provides a structure similar to what you would find on Microsoft Windows INI files. You can use this to write Python programs which can be customized by end users easily.

Importing a long list of constants to a Python file

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