Detect python version in shell script

Question

I\'d like to detect if python is installed on a Linux system and if it is, which python version is installed.

How can I do it? Is there something more graceful than

Answer 1

python -c 'import sys; print sys.version_info'

or, human-readable:

python -c 'import sys; print(".".join(map(str, sys.version_info[:3])))'

Answer 2

In case you need a bash script, that echoes "NoPython" if Python is not installed, and with the Python reference if it is installed, then you can use the following check_python.sh script.

• To understand how to use it in your app, I've also added my_app.sh.
• Check that it works by playing with PYTHON_MINIMUM_MAJOR and PYTHON_MINIMUM_MINOR

check_python.sh

#!/bin/bash

# Set minimum required versions
PYTHON_MINIMUM_MAJOR=3
PYTHON_MINIMUM_MINOR=6

# Get python references
PYTHON3_REF=$(which python3 | grep "/python3")
PYTHON_REF=$(which python | grep "/python")

error_msg(){
    echo "NoPython"
}

python_ref(){
    local my_ref=$1
    echo $($my_ref -c 'import platform; major, minor, patch = platform.python_version_tuple(); print(major); print(minor);')
}

# Print success_msg/error_msg according to the provided minimum required versions
check_version(){
    local major=$1
    local minor=$2
    local python_ref=$3
    [[ $major -ge $PYTHON_MINIMUM_MAJOR && $minor -ge $PYTHON_MINIMUM_MINOR ]] && echo $python_ref || error_msg
}

# Logic
if [[ ! -z $PYTHON3_REF ]]; then
    version=($(python_ref python3))
    check_version ${version[0]} ${version[1]} $PYTHON3_REF
elif [[ ! -z $PYTHON_REF ]]; then
    # Didn't find python3, let's try python
    version=($(python_ref python))
    check_version ${version[0]} ${version[1]} $PYTHON_REF
else
    # Python is not installed at all
    error_msg
fi

my_app.sh

#!/bin/bash
# Add this before your app's code
PYTHON_REF=$(source ./check_python.sh) # change path if necessary
if [[ "$PYTHON_REF" == "NoPython" ]]; then
    echo "Python3.6+ is not installed."
    exit
fi

# This is your app
# PYTHON_REF is python or python3
$PYTHON_REF -c "print('hello from python 3.6+')";

Answer 3

You can use this command in bash:

PYV=`python -c "import sys;t='{v[0]}.{v[1]}'.format(v=list(sys.version_info[:2]));sys.stdout.write(t)";`
echo $PYV

Answer 4

If you need to check if version is at least 'some version', then I prefer solution which doesn't make assumptions about number of digits in version parts.

VERSION=$(python -V 2>&1 | cut -d\  -f 2) # python 2 prints version to stderr
VERSION=(${VERSION//./ }) # make an version parts array 
if [[ ${VERSION[0]} -lt 3 ]] || [[ ${VERSION[0]} -eq 3 && ${VERSION[1] -lt 5 ]] ; then
    echo "Python 3.5+ needed!" 1>&2
    return 1
fi

This would work even with numbering like 2.12.32 or 3.12.0, etc. Inspired by this answer.

Answer 5

using sys.hexversion could be useful if you want to compare version in shell script

ret=`python -c 'import sys; print("%i" % (sys.hexversion<0x03000000))'`
if [ $ret -eq 0 ]; then
    echo "we require python version <3"
else 
    echo "python version is <3"
fi

Answer 6

Yet another way to print Python version in a machine-readable way with major and minor version number only. For example, instead of "3.8.3" it will print "38", and instead of "2.7.18" it will print "27".

python -c "import sys; print(''.join(map(str, sys.version_info[:2])))"

Works for both Python 2 and 3.