What version of Python do I have?

Question

How can I find out what versions of Python I have?

I am using Ubuntu 14.04 (Trusty Tahr).

Answer 1

You can use python -V (et al.) to show you the version of Python that the python command resolves to. If that's all you need, you're done. But to see every version of python in your system takes a bit more.

In Ubuntu we can check the resolution with readlink -f $(which python). In default cases in 14.04 this will simply point to /usr/bin/python2.7.

We can chain this in to show the version of that version of Python:

$ readlink -f $(which python) | xargs -I % sh -c 'echo -n "%: "; % -V'
/usr/bin/python2.7: Python 2.7.6

But this is still only telling us what our current python resolution is. If we were in a Virtualenv (a common Python stack management system) python might resolve to a different version:

$ readlink -f $(which python) | xargs -I % sh -c 'echo -n "%: "; % -V'
/home/oli/venv/bin/python: Python 2.7.4

This is real output.

The fact is there could be hundreds of different versions of Python secreted around your system, either on paths that are contextually added, or living under different binary names (like python3).

If we assume that a Python binary is always going to be called python<something> and be a binary file, we can just search the entire system for files that match those criteria:

$ sudo find / -type f -executable -iname 'python*' -exec file -i '{}' \; | awk -F: '/x-executable; charset=binary/ {print $1}' | xargs readlink -f | sort -u | xargs -I % sh -c 'echo -n "%: "; % -V'
/home/oli/venv/bin/python: Python 2.7.4
/media/ned/websites/venvold/bin/python: Python 2.7.4
/srv/chroot/precise_i386/usr/bin/python2.7: Python 2.7.3
/srv/chroot/trusty_i386/usr/bin/python2.7: Python 2.7.6
/srv/chroot/trusty_i386/usr/bin/python3.4: Python 3.4.0
/srv/chroot/trusty_i386/usr/bin/python3.4m: Python 3.4.0
/usr/bin/python2.7: Python 2.7.6
/usr/bin/python2.7-dbg: Python 2.7.6
/usr/bin/python3.4: Python 3.4.0
/usr/bin/python3.4dm: Python 3.4.0
/usr/bin/python3.4m: Python 3.4.0
/web/venvold/bin/python: Python 2.7.4

It's obviously a pretty hideous command but this is again real output and it seems to have done a fairly thorough job.

Answer 2

Type following in the terminal (Ctrl+Alt+T):

python -V

or

python --version

---

You can find a list of options/parameters for many commands in the terminal by typing the command followed by --help

Example:

python --help

Manual/manpages also available for most of such CLI which can be displayed by man <command> (Ex: man python)

From man python:

COMMAND LINE OPTIONS
        -V ,  --version
              Prints the Python version number of the executable and exits.

There is also python3 installed on many machines, so you can do:

python3 --version

to find out what python 3.x you are running.

Answer 3

python --version

and

python2 --version

show the version of Python 2.x,

python3 --version

the installed version of Python 3.x

Answer 4

If you want to see all versions of Python available as commands in Bash, run compgen -c python. E.g:

$ compgen -c python | sort -u
python
python2
python2.7
python3
python3.4
python3.4m
python3m

If you want to get the version of each of the above:

compgen -c python | sort -u | grep -v -- '-config$' | while read -r p; do
    printf "%-14s  " "$p"
    "$p" --version
done

python         Python 2.7.6
python2        Python 2.7.6
python2.7      Python 2.7.6
python3        Python 3.4.3
python3.4      Python 3.4.3
python3.4m     Python 3.4.3
python3m       Python 3.4.3

Notes:

• This ignores aliases. For example if I had alias python=python3, the above would still show 2.7 for python. To include aliases, you could use eval (though this might be unsafe):

  eval "$p --version"
  

• I'm filtering out the python*-config programs with grep -v since they don't support the --version flag. For example:

  $ python3-config --version
  Usage: /usr/bin/python3-config --prefix|--exec-prefix|--includes|--libs|--cflags|--ldflags|--extension-suffix|--help|--abiflags|--configdir
  

Answer 5

When you run python in the terminal, it will produce output like this:

Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 

See the first line - Python 2.7.6.

Also run python3. I have 3.4.1

Python 3.4.1 (default, Jul 31 2014, 12:46:17) 
[GCC 4.8.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

However, this won't show you them all. If you have 2 or more python 3.X.x versions, you will only see the latest one.

By default on 14.04, you have 2.7.6 and 3.4.0. As you can see, I have updated to 3.4.1. I know that I still have 3.4.0 because when I go to /usr/bin I see python3.4, and if I run /usr/bin/python3.4 in the command line, I get 3.4.0, and running /usr/local/bin/python3.4 gives me 3.4.1

My pronouns are He / Him

Answer 6

You can also check Python version from code itself using platform module from standard library. There are two functions: platform.python_version() (returns string) and platform.python_version_tuple() (returns tuple). Script:

import platform

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

Running:

$ python test.py 
3.4.1
('3', '4', '1')
$ python2.7 test.py 
2.7.8
('2', '7', '8')

Answer 7

Easily, open the terminal and do the following:

Write

python

to verify your 2.x version In my case, it will appear:

Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.

For the 3.x, write:

python3

In my case, it appears:

Python 3.4.0 (default, Apr 11 2014, 13:05:11) 
[GCC 4.8.2] on linux
Type "help", "copyright", "credits" or "license" for more information.

For both cases, to get out from Python shell, write:

 exit()

Answer 8

• In shell terminal

  $ which -a python lists all your python.

  $ which -a python2.7 lists all your python2.7.

  $ /usr/bin/python -V gives information about the version of /usr/bin/python.

• check in python script

here is an ilustration in ipython shell:

In [1]: import sys

In [2]: sys.version
2.7.11 |Anaconda 2.5.0 (64-bit)| (default, Dec  6 2015, 18:08:32) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)]

In [3]: sys.version_info
sys.version_info(major=2, minor=7, micro=11, releaselevel='final', serial=0)

In [4]: sys.version_info >= (2,7)
Out[4]: True

In [5]: sys.version_info >= (3,)
Out[5]: False

Answer 9

For bash script to recognize which python command to use:

#!/usr/bin/env bash

usage() {
    echo "Put your help/usage explanation here"
    exit 1
}

get_python_version_to_use() {
    if python3 --version 2>&1 | grep -q "Python 3" ; then 
        echo "python3"
    elif python --version 2>&1 | grep -q "Python 3"; then
        echo "python"
    elif python --version 2>&1 | grep -q "Python 2" ; then 
        echo "python"
    else 
        echo "Error: Python not found";
        usage
    fi
}

PYTHON_COMMAND=$(get_python_version_to_use)
echo $PYTHON_COMMAND

Now you can use it to run your script in the bash shell:

PYTHON_COMMAND=$(get_python_version_to_use)

$PYTHON_COMMAND my_script.py

And it will use python3 or python2 according to what installed on your machine (Preferring python3)