How do I check what version of Python is running m

Question

How can I check what version of the Python Interpreter is interpreting my script?

Answer 1

Here's a short commandline version which exits straight away (handy for scripts and automated execution):

python -c "print(__import__('sys').version)"

Or just the major, minor and micro:

python -c "print(__import__('sys').version_info[:1])" # (2,)
python -c "print(__import__('sys').version_info[:2])" # (2, 7)
python -c "print(__import__('sys').version_info[:3])" # (2, 7, 6)

Answer 2

Several answers already suggest how to query the current python version. To check programmatically the version requirements, I'd make use of one of the following two methods:

# Method 1: (see krawyoti's answer)
import sys
assert(sys.version_info >= (2,6))

# Method 2: 
import platform
from distutils.version import StrictVersion 
assert(StrictVersion(platform.python_version()) >= "2.6")

Answer 3

sys.version_info doesn't seem to return a tuple as of 3.7. Rather, it returns a special class, so all of the examples using tuples don't work, for me at least. Here's the output from a python console:

>>> import sys
>>> type(sys.version_info)
<class 'sys.version_info'>

I've found that using a combination of sys.version_info.major and sys.version_info.minor seems to suffice. For example,...

import sys
if sys.version_info.major > 3:
    print('Upgrade to Python 3')
    exit(1)

checks if you're running Python 3. You can even check for more specific versions with...

import sys
ver = sys.version_info
if ver.major > 2:
    if ver.major == 3 and ver.minor <= 4:
        print('Upgrade to Python 3.5')
        exit(1)

can check to see if you're running at least Python 3.5.

Answer 4

Your best bet is probably something like so:

>>> import sys
>>> sys.version_info
(2, 6, 4, 'final', 0)
>>> if not sys.version_info[:2] == (2, 6):
...    print "Error, I need python 2.6"
... else:
...    from my_module import twoPointSixCode
>>> 

Additionally, you can always wrap your imports in a simple try, which should catch syntax errors. And, to @Heikki's point, this code will be compatible with much older versions of python:

>>> try:
...     from my_module import twoPointSixCode
... except Exception: 
...     print "can't import, probably because your python is too old!"
>>>

Answer 5

Like Seth said, the main script could check sys.version_info (but note that that didn't appear until 2.0, so if you want to support older versions you would need to check another version property of the sys module).

But you still need to take care of not using any Python language features in the file that are not available in older Python versions. For example, this is allowed in Python 2.5 and later:

try:
    pass
except:
    pass
finally:
    pass

but won't work in older Python versions, because you could only have except OR finally match the try. So for compatibility with older Python versions you need to write:

try:
    try:
        pass
    except:
        pass
finally:
    pass

Answer 6

From the command line (note the capital 'V'):

python -V

This is documented in 'man python'.