How can I check for Python version in a program that uses new language features?

Question

You can test using eval:

try:
  eval("1 if True else 2")
except SyntaxError:
  # doesn't have ternary

Also, with is available in Python 2.5, just add from __future__ import with_statement.

EDIT: to get control early enough, you could split it into different .py files and check compatibility in the main file before importing (e.g. in __init__.py in a package):

# __init__.py

# Check compatibility
try:
  eval("1 if True else 2")
except SyntaxError:
  raise ImportError("requires ternary support")

# import from another module
from impl import *

Have a wrapper around your program that does the following.

import sys

req_version = (2,5)
cur_version = sys.version_info

if cur_version >= req_version:
   import myApp
   myApp.run()
else:
   print "Your Python interpreter is too old. Please consider upgrading."

You can also consider using sys.version(), if you plan to encounter people who are using pre-2.0 Python interpreters, but then you have some regular expressions to do.

And there might be more elegant ways to do this.

Try

import platform
platform.python_version()

Should give you a string like "2.3.1". If this is not exactly waht you want there is a rich set of data available through the "platform" build-in. What you want should be in there somewhere.

Probably the best way to do do this version comparison is to use the sys.hexversion. This is important because comparing version tuples will not give you the desired result in all python versions.

import sys
if sys.hexversion < 0x02060000:
    print "yep!"
else:
    print "oops!"

import sys    
# prints whether python is version 3 or not
python_version = sys.version_info.major
if python_version == 3:
    print("is python 3")
else:
    print("not python 3")

Answer from Nykakin at AskUbuntu:

You can also check Python version from code itself using platform module from standard library.

There are two functions:

• platform.python_version() (returns string).
• platform.python_version_tuple() (returns tuple).

---

The Python code

Create a file for example: version.py)

Easy method to check version:

import platform

print(platform.python_version())
print(platform.python_version_tuple())

You can also use the eval method:

try:
  eval("1 if True else 2")
except SyntaxError:
  raise ImportError("requires ternary support")

---

Run the Python file in a command line:

$ python version.py 
2.7.11
('2', '7', '11')

The output of Python with CGI via a WAMP Server on Windows 10:

---

Helpful resources

• https://askubuntu.com/questions/505081/what-version-of-python-do-i-have

Sets became part of the core language in Python 2.4, in order to stay backwards compatible. I did this back then, which will work for you as well:

if sys.version_info < (2, 4):
    from sets import Set as set