How do I detect the Python version at runtime?
PythonPython Problem Overview
I have a Python file which might have to support Python versions < 3.x and >= 3.x. Is there a way to introspect the Python runtime to know the version which it is running (for example, 2.6 or 3.2.x
)?
Python Solutions
Solution 1 - Python
Sure, take a look at sys.version
and sys.version_info
.
For example, to check that you are running Python 3.x, use
import sys
if sys.version_info[0] < 3:
raise Exception("Must be using Python 3")
Here, sys.version_info[0]
is the major version number. sys.version_info[1]
would give you the minor version number.
In Python 2.7 and later, the components of sys.version_info
can also be accessed by name, so the major version number is sys.version_info.major
.
Solution 2 - Python
Try this code, this should work:
import platform
print(platform.python_version())
Solution 3 - Python
Per sys.hexversion and API and ABI Versioning:
import sys
if sys.hexversion >= 0x3000000:
print('Python 3.x hexversion %s is in use.' % hex(sys.hexversion))
Solution 4 - Python
Just in case you want to see all of the gory details in human readable form, you can use:
import platform;
print(platform.sys.version);
Output for my system:
3.6.5 |Anaconda, Inc.| (default, Apr 29 2018, 16:14:56)
[GCC 7.2.0]
Something very detailed but machine parsable would be to get the version_info
object from platform.sys
, instead, and then use its properties to take a predetermined course of action. For example:
import platform;
print(platform.sys.version_info)
Output on my system:
sys.version_info(major=3, minor=6, micro=5, releaselevel='final', serial=0)
Solution 5 - Python
The best solution depends on how much code is incompatible. If there are a lot of places you need to support Python 2 and 3, six
is the compatibility module. six.PY2
and six.PY3
are two booleans if you want to check the version.
However, a better solution than using a lot of if
statements is to use six
compatibility functions if possible. Hypothetically, if Python 3000 has a new syntax for next
, someone could update six
so your old code would still work.
import six
# OK
if six.PY2:
x = it.next() # Python 2 syntax
else:
x = next(it) # Python 3 syntax
# Better
x = six.next(it)
Solution 6 - Python
Here's some code I use with sys.version_info
to check the Python installation:
def check_installation(rv):
current_version = sys.version_info
if current_version[0] == rv[0] and current_version[1] >= rv[1]:
pass
else:
sys.stderr.write( "[%s] - Error: Your Python interpreter must be %d.%d or greater (within major version %d)\n" % (sys.argv[0], rv[0], rv[1], rv[0]) )
sys.exit(-1)
return 0
...
# Calling the 'check_installation' function checks if Python is >= 2.7 and < 3
required_version = (2,7)
check_installation(required_version)
Solution 7 - Python
To make the scripts compatible with Python2 and 3 i use :
from sys import version_info
if version_info[0] < 3:
from __future__ import print_function
Solution 8 - Python
Version check example below.
Note that I do not stop the execution, this snippet just:
-
do nothing if exact version matches
-
write INFO if revision (last number) is different
-
write WARN if any of major+minor are different
import sys import warnings
def checkVersion(): # Checking Python version: expect_major = 2 expect_minor = 7 expect_rev = 14 if sys.version_info[:3] != (expect_major, expect_minor, expect_rev): print("INFO: Script developed and tested with Python " + str(expect_major) + "." + str(expect_minor) + "." + str(expect_rev)) current_version = str(sys.version_info[0])+"."+str(sys.version_info[1])+"."+str(sys.version_info[2]) if sys.version_info[:2] != (expect_major, expect_minor): warnings.warn("Current Python version was unexpected: Python " + current_version) else: print(" Current version is different: Python " + current_version)
Solution 9 - Python
Since all you are interested in is whether you have Python 2 or 3, a bit hackish but definitely the simplest and 100% working way of doing that would be as follows:
python_version_major = 3/2*2
The only drawback of this is that when there is Python 4, it will probably still give you 3.