How to Make Python 3 the Default Version on Your Mac, Linux, or Windows?

Changing the Default Python Version

Problem:

Python 2.6.1 remains active despite installing Python 3.2 on a Mac, leading to confusion when typing python -V in Terminal.

Solution:

Regardless of the operating system (Mac, Linux, or Windows), python3 can be invoked without affecting Python 2 installations.

Historical Context:

Historically, scripts called python2 or python3 explicitly to maintain backwards compatibility. Python3 significantly departed from this practice, potentially breaking older scripts dependent on python=python2. To avoid this, the python command was left unchanged, allowing users to maintain compatibility for legacy applications.

Current Practice:

Today, most software explicitly refers to python2 or python3, freeing up the python command for user customization. However, this may vary depending on the operating system.

Specific Platform Considerations:

• Mac: The python command can be set as a user default in the Terminal Preferences or through a shell alias.
• Linux: The distribution's package management system can be used to manage Python versions, and alternatives can be set using sudo update-alternatives.
• Windows: The registry can be used to set the default Python version through the PATH environment variable.

Understanding $PATH:

The PATH environment variable determines which directories are searched for executable files. The first match in the first directory is executed. For example, the python command may be a symlink to a specific version of Python installed on the system.

Additional Notes:

• Different Python 3 Versions: If multiple Python 3 versions are installed, the PATH can be modified to select the desired default version.
• Python Environments: Virtual environments can be considered a better option for managing different Python versions than creating aliases or manipulating $PATH.

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