How to Install Python Packages with pip and requirements.txt

This article explains how to install Python packages using pip and requirements.txt.

• User Guide - pip documentation v25.1

For basic usage of pip, including how to install, update, and uninstall packages, see the following article.

• How to use pip (Install, update, uninstall packages)

Install packages with pip and requirements.txt

The following command installs multiple packages at once based on a configuration file, typically named requirements.txt. In some environments, you may need to use pip3 instead of pip.

$ pip install -r requirements.txt

You can name the configuration file arbitrarily, though requirements.txt is commonly used.

Place requirements.txt in the directory where you plan to run the command. If the file is in a different directory, specify its path, such as path/to/requirements.txt.

How to write requirements.txt

An example of a requirements.txt file is shown below.

###### Requirements without Version Specifiers ######
nose
nose-cov
beautifulsoup4
#
###### Requirements with Version Specifiers ######
#   See https://www.python.org/dev/peps/pep-0440/#version-specifiers
docopt == 0.6.1             # Version Matching. Must be version 0.6.1
keyring >= 4.1.1            # Minimum version 4.1.1
coverage != 3.5             # Version Exclusion. Anything except version 3.5
Mopidy-Dirble ~= 1.1        # Compatible release. Same as >= 1.1, == 1.*

As with Python code, comments can be included in requirements.txt using #.

• How to write a comment and comment out lines in Python

You can specify package versions using operators like ==, >, >=, <, and <=. If you omit the version specifier, the latest version will be installed.

Two conditions can be combined with AND by separating them with a comma. In the following example, a version >= 1.0 and <= 2.0 will be installed.

package >= 1.0, <= 2.0

Refer to the official documentation for detailed specifications.

• Requirements File Format - pip documentation v25.1
• Requirement Specifiers - pip documentation v25.1
• Version specifiers - Python Packaging User Guide

Create requirements.txt with pip freeze

pip freeze outputs a list of the packages installed in the current environment along with their versions, in a format that can be used as requirements.txt.

• List installed Python packages with pip list/freeze

$ pip freeze
agate==1.6.0
agate-dbf==0.2.0
agate-excel==0.2.1
agate-sql==0.5.2
...

You can use the redirection operator (>) to save the pip freeze output to a file. This file can be used to install the same package versions in a different environment.

First, redirect the pip freeze output to a file named requirements.txt.

$ pip freeze > requirements.txt

Next, copy or move this requirements.txt file to a different environment and use it to install the packages.

$ pip install -r requirements.txt

By following these steps, you can easily replicate the exact package setup from one environment to another.