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Python virtual environment

A Python virtual environment is an isolated environment where you can
install Python packages without interfering with other projects or the
system's Python interpreter. It's a way to manage dependencies on a
per-project basis. This is particularly useful when different projects
require different versions of the same package.

Advantages

Python virtual environments offer several advantages:

  1. Dependency Management: Each project can have its own dependencies,
    independent of other projects.

  2. Version Control: Different projects can use different versions of
    the same package without conflict.

  3. Isolation: Changes within a virtual environment do not affect
    the system's Python interpreter or other projects.

  4. Simplicity: It's easy to create, use, and delete Python virtual
    environments.

Commands

  1. Create a virtual environment:
    py -m venv myenv

  2. Activate the virtual environment:

    • On Windows: myenv\Scripts\activate
    • On Unix or MacOS: source ./myenv/bin/activate

  3. Deactivate the virtual environment:
    deactivate

  4. Install packages using pip:
    pip install package-name

  5. List installed packages:
    pip list

  6. Remove packages:
    pip uninstall package-name

requirements.txt

A requirements.txt file is a plain text file used in Python projects to list
out the external libraries or packages that the project depends on. These
libraries are not part of the Python standard library and need to be installed
separately.

Here are some key points about requirements.txt:

Function: It specifies the exact dependencies needed for a project, ensuring
everyone working on the project has the same environment set up. This promotes
reproducibility and avoids compatibility issues.

Benefits:
Easy Installation: With requirements.txt, you can install all the required
packages at once using the pip install -r requirements.txt command. This saves
time and avoids manual installation of each package.

Collaboration: When you share your project, others can easily set up their
environment by installing the dependencies listed in the requirements.txt file.

Location: The requirements.txt file is typically placed in the root directory
of your Python project.

Format: The file is a simple text file where each line specifies a package and
optionally its version. There are ways to specify version constraints as well
(e.g., installing a specific version range or the latest compatible version).

Overall, requirements.txt is a best practice for managing dependencies in
Python projects, promoting a consistent and efficient development workflow.

Once you've installed all the necessary packages for your project using pip,
you can generate a requirements.txt file that captures those dependencies
and their versions.

pip freeze > requirements.txt

The command lists all the installed Python packages and their versions in your
current virtual environment. The > redirects the output of the pip freeze command.
The requirements.txt file specifies the filename where the list of packages will
be saved.

The pip uninstall -r requirements.txt -y uninstalls all packages in the requirements.txt file.