Added pip article to the KB

knowledge base/pip.md

@@ -0,0 +1,57 @@
+# PIP
+
+Package installer for Python.
+
+1. [TL;DR](#tldr)
+2. [Configuration](#configuration)
+3. [Further readings](#further-readings)
+
+## TL;DR
+
+```sh
+# Install packages.
+pip install 'yamllint'
+pip install --user 'ansible'
+
+# Upgrade packages.
+pip install -U 'pip'
+
+# Upgrade the included `pip` executable on Mac OS X.
+~/Library/Python/3.8/bin/pip3 install --user --upgrade 'pip'
+
+# Upgrade all currently installed packages.
+pip install --requirement <(pip freeze | sed 's/==/>=/') --upgrade
+
+# Generate a list of the outdated packages.
+pip list --outdated
+
+# Remove orphaned dependencies.
+# Requires `pip-autoremove`.
+pip-autoremove
+```
+
+## Configuration
+
+INI format files, on those levels:
+
+Level | Scope | File locations
+---|---|---
+global | System-wide, shared | The `pip` subdirectory in any of the directories defined in `XDG_CONFIG_DIRS` if it exists (i.e. `/etc/xdg/pip/pip.conf`)<br/>`/etc/pip.conf`
+user | Per-user | `$HOME/.config/pip/pip.conf`<br/>`$HOME/.pip/pip.conf` (legacy)
+site | Per-environment | `$VIRTUAL_ENV/pip.conf`
+shell | Active shell session | Value of `PIP_CONFIG_FILE`
+
+When multiple configuration exist, pip **merges** them in the following order:
+
+1. shell
+1. global
+1. user
+1. site
+
+Latter files override values from previous files, i.e. the global timeout specified in the global file will be superseded by the one defined in the user file.
+
+## Further readings
+
+- [Configuration]
+
+[configuration]: https://pip.pypa.io/en/stable/topics/configuration/

knowledge base/python.md

@@ -18,23 +18,6 @@ F"{name.lower()} is funny."
 unique_list = list(set(redundant_list))
 ```
 
-Maintenance:
-
-```sh
-# Generate a list of the outdated packages.
-pip list --outdated
-
-# Upgrade all packages.
-pip install --requirement <(pip freeze | sed 's/==/>=/') --upgrade
-
-# Remove orphaned dependencies.
-# Requires `pip-autoremove`.
-pip-autoremove
-
-# Upgrade the included `pip` executable on Mac OS X.
-~/Library/Python/3.8/bin/pip3 install --user --upgrade pip
-```
-
 ## Web servers
 
 ### Flask
@@ -93,10 +76,11 @@ python hello.py
 
 ## Further readings
 
+- [PIP]
 - [How To Update All Python Packages]
 - [invl/pip-autoremove]
 - [Data types]
-- [F-strings
+- [F-strings]
 - [How to filter list elements in Python]
 - [Logging]
 - [Flask at first run: do not use the development server in a production environment]
@@ -106,6 +90,9 @@ python hello.py
 - [An intro to threading in Python]
 - [ThreadPoolExecutor in Python: the complete guide]
 
+<!-- internal references -->
+[pip]: ./pip.md
+
 <!-- external references -->
 [*args and **kwargs in python]: https://www.geeksforgeeks.org/args-kwargs-python/
 [an intro to threading in python]: https://realpython.com/intro-to-python-threading/