Version: Dec 20, 2024

Python Basics

Overview

Times keep changing for the tools we use. Since so many solutions are relaying on Python, Python has gotten to the point where it needs to be isolated so packages don't negatively impact each other.

This guide hopes to help those who run into issues with Python. Please note this guide is from the perspective of MacOS Sequoia.

Checking Python Version

For Python under 3 or python 3, respectively.
```
python --version
python3 --version
```

Locate Python

Find the exact locations of the Python executables:
```
which python
which python3
```
List Python Installed via Homebrew
```
brew list | grep python
```
You can check the version via pyenv
```
brew install pyenv
pyenv versions
```

Installing Python

Check Home Brew

Homnebrew is a good choice as package manager. Its good practice to update Homebrew is you have'nt done so.
```
brew --version
brew update
```
Then to install Python
```
brew install python
```

Updating PATH

Use the correct Python version. Homebrew installs Python in /usr/local/bin (Intel Macs) or /opt/homebrew/bin (M1/M2 Macs). Ensure that this version is prioritized in your PATH.

Add the following to your ~/.zshrc or ~/.bashrc (depending on your shell):

export PATH="/usr/local/bin:$PATH"  # For Intel Macs
export PATH="/opt/homebrew/bin:$PATH"  # For M1/M2 Macs

Reload your shell:
```
source ~/.zshrc
```

Install a Specific Version of Python

If you need a specific version of Python, you can use Homebrew’s python@x formula. For example:
Install Python 3.10:
```
brew install python@3.10
```
To use a specific version, link it to your default python3 command:
```
brew link --overwrite python@3.10
```

Setting up a Virtual Environment

This one was new to me, I need to know setup virtual environments to download packages and develop!

1. Prerequisites

Ensure you have Python installed. Verify the version:
```
python3 --version
```

2. Create a Virtual Environment

Navigate to Your Project Directory:
```
cd /path/to/your/project
```
Use Python’s built-in venv module to create the environment:
```
python3 -m venv venv_name
```
Replace venv_name with the desired name for the virtual environment (e.g., venv or env).
This creates a directory named venv_name containing the virtual environment.

3. Activate the Virtual Environment

macOS/Linux:
```
source venv_name/bin/activate
```
Windows:
```
venv_name\Scripts\activate
```
Once activated, you’ll see the environment name in your shell prompt, indicating that the virtual environment is active, e.g.:
```
(venv_name) user@computer:~/project$
```
To exit the virtual environment:
```
deactivate
```

4. Install Packages

This will install packages locally to the virtual environment only, which is the point of it.
Once you deactivate, the packages are no longer reachable, but they are still there in the project directory.
Inside the virtual environment, you can use pip to install packages:
```
pip install package_name
```
Example:
```
pip install numpy
```
List current packages:
```
pip list
```

5. Re-Activate the Environment

If you need to work on the project again, re-activate the virtual environment:

source venv_name/bin/activate  # macOS/Linux
venv_name\Scripts\activate     # Windows

6. Save and Reuse Dependencies

To share your environment with others or recreate it via export installed packages:
```
pip freeze > requirements.txt
```
Reinstall Dependencies in a New Environment:
```
pip install -r requirements.txt
```
Delete a Virtual Environment
```
rm -rf venv_name
```

7. Using Virtual Environments with IDEs

Most modern IDEs (like VSCode or PyCharm) detect and integrate with virtual environments automatically.
VSCode:
- Install the Python extension.
- Open the Command Palette (Ctrl+Shift+P or Cmd+Shift+P)
- Select “Python: Select Interpreter” and choose the virtual environment.
PyCharm:
- Go to “Settings” → “Project Interpreter.”
- Add your virtual environment as a new interpreter.

By using virtual environments, you can keep your Python projects organized and avoid dependency conflicts. Cheers!