Python Good Starting

When beginning your journey with Python, it’s crucial to set up your development environment properly to avoid potential conflicts and ensure a smooth experience. This guide will walk you through the steps of installing Python correctly using pyenv, managing different Python versions, and setting up a virtual environment for your projects.

Table of Contents

Why Learn Python Correctly from Scratch?

  • Consistency Across Environments: Setting up a consistent Python environment ensures that your code runs the same way on different systems.
  • Avoid System Conflicts: Using tools like pyenv and virtual environments prevents conflicts with system-installed Python versions and other projects.
  • Manage Dependencies: Virtual environments help you manage project-specific dependencies without affecting your global Python installation (useful for Linux users).

Pyenv

pyenv is a tool that allows you to easily install and manage multiple versions of Python. It helps you avoid conflicts with the system Python and manage different versions for different projects.

1. To install pyenv:

On macOS/Linux:

curl https://pyenv.run | bash

2. Configure Shell for pyenv

After running the command, add the following lines to your shell startup file (.bashrc, .zshrc, etc.):

# Pyenv configuration
export PATH="$HOME/.pyenv/bin:$PATH"
eval "$(pyenv init --path)"
eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"

This step is also important to avoid pip conflicts. Create an alias in .bashrc, .zshrc, etc., to ensure you are using pip from the correct pyenv installation:

# Configure your PIP as well
alias pip='python -m pip'

3. Restart Shell

Restart your shell or run source ~/.bashrc (or the corresponding file) to apply the changes.

4. Check Available Python Versions:

To see the available Python versions that you can install with pyenv, use:

pyenv install --list

5. Install a Python Version with pyenv

To install a specific version of Python, use:

# Replace <version> with the desired version number (e.g., 3.9.1).
pyenv install <version>

6. Check Installed Python Versions

To see which Python versions are installed on your system and identify the active version:

pyenv versions

# Example Output:
  system # Python from your system
  3.7.17
* 3.11.9 # (the * represents the active version)
  3.12.0

7. Select a Python Version

pyenv global <python-version>

VirtualEnv

virtualenv is a tool to create isolated Python environments, ensuring that dependencies for one project don’t interfere with those of another.

1. Install virtualenv

pip install virtualenv

2. Create a Virtual Environment with virtualenv

Select the directory where you will start your project (typically a new folder), then run:

# You don't need to specify the python version because pyenv is doing it when you
# choose the global version that you want to use on the previous steps. Of course
# if you want to change the python version, you have to do it on pyenv first before
# execute this command.
virtualenv --python=python <python-env-name>
# Recommended to use "env" as the environment name

3. Activate the Virtual Environment

source <python-env-name>/bin/activate

When the environment is active, its name appears at the beginning of your terminal prompt:

(<python-env-name>) user@machine:~/<project-directory>$

Install Dependencies

After creating and activating the virtual environment, it’s a good practice to create a requirements.txt file listing the Python libraries required for the project:

# requirements.txt file
requests==2.25.1
selenium==4.4.1
bs4==0.0.2
klein_config==4.0.2

Install all dependencies at once from requirements.txt:

pip install -r requirements.txt

Project Structure Overview

Here’s an example of a simple, well-organized Python project structure:

my_project/
├── app/                 # Your application
├── env/                 # Virtual environment directory (exclude from version control)
├── requirements.txt     # List of project dependencies
├── .gitignore           # Files and directories to ignore in Git
└── README.md            # Project overview and documentation