check python version(s) from within a python script and if/else based on that

Question

Basically I'd like to know if there is a way to know what version of python a script is using from within the script? Here's my current example of where I'd like to use it:

I would like to make a python script use unicode if it is using python 2, but otherwise not use unicode. I currently have python 2.7.5 and python 3.4.0 installed, and am running my current project under python 3.4.0. The following scirpt:

_base = os.path.supports_unicode_filenames and unicode or str

was returning the error:

    _base = os.path.supports_unicode_filenames and unicode or str
NameError: name 'unicode' is not defined

So I changed it to this in order to get it to work:

_base = os.path.supports_unicode_filenames and str

Is there a way to change it to something to this effect:

if python.version == 2:

    _base = os.path.supports_unicode_filenames and unicode or str

else:

    _base = os.path.supports_unicode_filenames and str

Vor · Accepted Answer · 2014-04-05 19:35:26Z

4

You are very close:

import sys
sys.version_info

Would return:

sys.version_info(major=2, minor=7, micro=4, releaselevel='final', serial=0)

and you can do something like this:

import sys
ver = sys.version_info[0]
if ver == 2:
    pass

answered Apr 5, 2014 at 19:35

Vor

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Comments

jfs · Accepted Answer · 2014-04-05 22:26:57Z

2

You could define unicode for Python 3:

try:
    unicode = unicode
except NameError: # Python 3 (or no unicode support)
    unicode = str # str type is a Unicode string in Python 3

To check version, you could use sys.version, sys.hexversion, sys.version_info:

import sys

if sys.version_info[0] < 3:
   print('before Python 3 (Python 2)')
else: # Python 3
   print('Python 3 or newer')

answered Apr 5, 2014 at 22:26

jfs

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1 Comment

Aaron Lelevier Over a year ago

I marked this as the accepted answer since it hit the nail on the head, for handling the "can't find 'unicode' error" and how to proceed.

anon582847382 · Accepted Answer · 2014-04-05 19:36:12Z

2

Use sys.version_info to check your Python version. For example:

import sys

if sys.version_info[0] == 2:
    ... stuff
else:
    ... stuff

answered Apr 5, 2014 at 19:36

anon582847382

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Comments

Daniel Roseman · Accepted Answer · 2014-04-05 19:43:29Z

2

You should probably look into the six library to better support the differences between Python 2 and 3.

answered Apr 5, 2014 at 19:43

Daniel Roseman

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1 Comment

Aaron Lelevier Over a year ago

Thanks Daniel Roseman. That library looks super useful. I'm gonna have to start using more, and then definitely it would work in this case.

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