Question
Answer and Explanation
Pyenv manages Python versions at different scopes, and its local settings are designed to take precedence over global ones. Here’s how this overriding mechanism works:
1. Pyenv's Layered Approach:
- Pyenv operates on a layered configuration model. It checks for Python versions in the following order, from most specific to least specific:
a. Local settings: These are typically defined using a .python-version file in your project directory.
b. Directory settings: If a .python-version file is not found in the current directory, pyenv will look in its parent directories.
c. Global settings: If no local or directory settings are found, pyenv falls back to the version set globally using pyenv global .
2. The .python-version file:
- When you use pyenv local in a project directory, Pyenv creates (or modifies) a .python-version file in that directory. This file contains the name of the Python version to be used for that project.
3. How local overrides global:
- When you execute a Python script or command, pyenv searches for the .python-version file in the current directory, then traverses upwards through parent directories. If it finds such a file, it will use the version specified in this file. This effectively overrides any global settings set by pyenv global.
4. Example Scenarios:
- Scenario 1: Global Python 3.9, Local Project 3.10
- If you've set your global version to Python 3.9 with pyenv global 3.9, but you have a project directory with a .python-version file containing 3.10, Pyenv will use Python 3.10 when executing Python commands inside that project directory.
- Scenario 2: Nested projects:
- If you have nested projects, pyenv will always use the nearest (in terms of directory hierarchy) .python-version. For instance, if a parent folder has a .python-version with 3.8, and a subfolder has its .python-version with 3.11, the subfolder will use version 3.11
5. Explanation of precedence:
- This behavior allows for different projects to use different Python versions without interfering with each other or system wide Python installation. pyenv essentially modifies your shell’s PATH environment variable during execution to point to the correct Python executable.
6. Viewing active version
- You can always confirm the active Python version in your current directory by using the command pyenv version.
In summary, Pyenv's local settings, as specified in a .python-version file, will override global settings because it searches from the current directory upwards, prioritizing closer settings over those set globally.