Third-party libraries and pip

You need to call someone else's API, parse a web page, or analyze a table with a million rows. The standard library has some of this, but the community has written far handier tools: requests, beautifulsoup4, pandas, and thousands more. These are third-party libraries — what isn't part of Python's distribution and is installed separately with pip, the standard package manager.

What are third-party libraries?

What is pip?

Installing and using pip

Usually pip is already installed along with Python. You can check the presence and version of pip like this:

pip --version

Expected result:

pip 23.1.2 from /usr/local/lib/python3.11/site-packages/pip (python 3.11)

Basic pip commands

Installing a package

pip install requests

Expected result:

Collecting requests
  Downloading requests-2.31.0-py3-none-any.whl (62 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 62.6/62.6 kB 1.2 MB/s eta 0:00:00
Installing collected packages: requests
Successfully installed requests-2.31.0

Installing a specific version

pip install requests==2.25.1

Expected result:

Collecting requests==2.25.1
  Downloading requests-2.25.1-py2.py3-none-any.whl (61 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 61.2/61.2 kB 1.8 MB/s eta 0:00:00
Installing collected packages: requests
Successfully installed requests-2.25.1

List of installed packages

pip list

Expected result:

Package    Version
---------- ---------
certifi    2023.5.7
charset-normalizer 3.1.0
idna       3.4
pip        23.1.2
requests   2.31.0
setuptools 67.8.0
urllib3    2.0.3

Removing a package

pip uninstall requests -y

Expected result:

Found existing installation: requests 2.31.0
Uninstalling requests-2.31.0:
  Successfully uninstalled requests-2.31.0

Popular third-party libraries

Python has a huge number of third-party libraries for a wide variety of tasks. Here are some of the most popular and useful:

The choice of library depends on the specific task you want to solve. The Python community is very active, and ready-made solutions already exist for most practical tasks, which can be installed via pip.

Example of installing a popular library:

# Installing pandas for data analysis
pip install pandas

# Installing Flask for web development
pip install flask

Virtual environments

If you install every library into your system Python, sooner or later you'll hit a conflict: one project needs django 3.0, another needs django 4.2, but only one version can be installed. The standard practice is to create a separate virtual environment for each project.

Creating a virtual environment

# Creating a virtual environment
python -m venv myenv

# Activating the virtual environment
# On Windows:
myenv\Scripts\activate

# On macOS/Linux:
source myenv/bin/activate

# After activation, the environment name will appear at the beginning of the command prompt
(myenv) $

Installing packages in a virtual environment

# Installing packages in the activated virtual environment
pip install pandas matplotlib

Saving and installing dependencies

# Saving the list of installed packages
pip freeze > requirements.txt

# The contents of the requirements.txt file will look something like this:
# matplotlib==3.7.2
# numpy==1.25.2
# pandas==2.0.3
# ...

# Installing packages from the requirements.txt file
pip install -r requirements.txt

Understanding Check

Which command will correctly install pandas version 1.5.0?