python: more notes on package management

Programming_Languages/Python/Concepts/Python_package_management.md

@@ -6,20 +6,44 @@ tags: [python, data-types]
 
 # Package management
 
-- It is better to use `conda` (the package manager that comes with `anaconda`), since this makes it easier to work with conflicting package libraries (a bit like a package lock).
+- You can use `conda` (the package manager that comes with `anaconda`). This makes it easier to work with conflicting package libraries (a bit like a package lock).
 
 - The alternative is the native `pip` but you have to create virtual environments (`venv`) to manage packages at different versions.
 
-  It works a bit like this:
+To make use of virtual environments in `pip` you have to create the virtual environment before installing anything:
 
-  ![](/_img/Screenshot%202023-02-13%20at%2010.43.17.png)
+```
+python3 -m venv venv
+source venv3/bin/activate
+pip [library_name]
+```
 
-  To make use of virtual environments in `pip` you have to create the virtual environment before installing anything:
+This will create a `venv` directory in your project that will manage the handling of modules.
 
-  ```
-  python3 -m venv venv3
-  source venv3/bin/activate
-  pip [library_name]
-  ```
+> This is especially important in ArchLinux since without a virtual environment it will ask you to install packages with `pacman` which is annoying for local packages.
 
-- pypi.org > is package registry like NPM
+## requirements.txt
+
+The `requirements.txt` file is similar to the `package.json` in Node projects.
+
+Each line of the `requirements.txt`` file specifies a package that your project depends on and, optionally, the desired version of that package. When you share your project with others or move it between different environments (e.g., from development to production), this file makes it easy to set up your environment with the right dependencies.
+
+### Example
+
+```
+Flask==1.1.2
+requests>=2.24.0
+numpy~=1.19.2
+pandas
+```
+
+### Generate requirements file
+
+```
+pip freeze > requirements.txt
+
+```
+
+## Pypy
+
+- pypi.org is package registry like NPM