How Do I Set the Default Python Version?

How to Select the Default Python Version

Changing the Default Version

Historically, Python versions coexisted due to compatibility concerns. To maintain backwards compatibility, newer Python versions (e.g., Python 3) did not replace Python 2 when installed. This resulted in the confusing situation where typing "python" would invoke Python 2, even after installing Python 3.

However, modern systems encourage explicitly calling specific Python versions (e.g., "python2" or "python3") in scripts and commands.

Using a Shell Alias

To conveniently execute specific Python versions, create a shell alias. Here's an example for setting the default Python version to Python 3:

alias py=python3

Configuring $PATH

The PATH environment variable controls which directories are searched for executable files. To prioritize specific Python versions, place the desired version's directory at the beginning of the path:

export PATH=/usr/local/bin/python3:$PATH

Different Python Versions and $PATH

If multiple Python versions (e.g., Python 3.1 and 3.2) are installed, the PATH variable determines which version is executed. The first occurrence of a matching program in the specified directories will be invoked.

Here's an example where "python3" resolves to Python 3.7:

echo $PATH
/usr/sbin:/usr/local/bin:/usr/sbin:usr/local/bin:/usr/bin:/bin

which python3
/usr/bin/python3

ls -l /usr/bin/python3
lrwxrwxrwx 1 root root 9 Mar 26  2019 /usr/bin/python3 -> python3.7*

ls -l /usr/bin/python3.7
-rwxr-xr-x 2 root root 4877888 Apr  2  2019 /usr/bin/python3.7*

Managing Virtual Environments

To isolate specific Python versions and their packages, consider using virtual environments. This allows for customized installations and independent version management.

The above is the detailed content of How Do I Set the Default Python Version?. For more information, please follow other related articles on the PHP Chinese website!