Detect is python program run with python or python3

Question

I have a python program that can be run both: with python or python3:

# that
python app.py

# or that
python3 app.py

How to detect inside app.py program which command was used?
I tried to use sys.argv, but it doesn't contains such info.
Any ideas?

Answer 1

Try sys.version_info, specifically sys.version_info.major, which should be 2 or 3, respectively.

A different way is using the six package, with the booleans six.PY2 and six.PY3. This package should give other useful utilities for 2/3 compatibility.