pip install -r requirements.txt: Install, Create and Fix Errors

Running pip install from a requirements txt file takes one command: activate your virtual environment in the project folder, then run pip install -r requirements.txt. pip reads every line and installs those packages and versions:

python -m venv .venv
.venv\Scripts\activate          # macOS/Linux: source .venv/bin/activate
pip install -r requirements.txt

Every command here really ran on Python 3.12.5 in Windows Command Prompt, installing two small packages from PyPI into a fresh virtual environment.

I’ll show what goes in the file, how to install it, how to create one with pip freeze, version specifiers, the errors you’re likely to hit, and the faster uv option.

What is a requirements.txt file?

It’s a plain text file listing the packages your project needs, one per line, usually with versions. Anyone can then recreate your setup with a single command instead of guessing what to install.

Line	Meaning
requests	Any version (latest at install time)
requests==2.32.3	Exactly this version
requests>=2.31	This version or newer
requests>=2.31,<3	At least 2.31 but below 3.0
requests~=2.32.0	Compatible release: 2.32.x only
# comment	Ignored by pip
-r base.txt	Include another requirements file

How to install requirements.txt with pip

Create a virtual environment first so the packages don’t land in your global Python. Then point pip at the file with -r:

# requirements.txt for the store-report project
tabulate==0.9.0        # exact version
colorama>=0.4.6,<0.5   # any 0.4.x from 0.4.6 up

Output:

Collecting tabulate==0.9.0 (from -r requirements.txt (line 2))
  Using cached tabulate-0.9.0-py3-none-any.whl.metadata (34 kB)
Collecting colorama<0.5,>=0.4.6 (from -r requirements.txt (line 3))
  Using cached colorama-0.4.6-py2.py3-none-any.whl.metadata (17 kB)
Using cached tabulate-0.9.0-py3-none-any.whl (35 kB)
Using cached colorama-0.4.6-py2.py3-none-any.whl (25 kB)
Installing collected packages: tabulate, colorama
Successfully installed colorama-0.4.6 tabulate-0.9.0
Package  Version
-------- -------
colorama 0.4.6
pip      24.2
tabulate 0.9.0

Using python -m pip instead of plain pip guarantees you’re installing into the Python you think you are. Inside an activated venv both are the same.

Need just one package at a particular version? See pip install a specific version. And for more on environments, Python virtual environments.

Creating a requirements.txt file with pip freeze

Once your project works, pip freeze lists every installed package with its exact version. Redirect it to a file and you’ve captured the environment:

from colorama import Fore, Style, just_fix_windows_console
from tabulate import tabulate

just_fix_windows_console()
rows = [["Austin", 1250.50], ["Denver", 980.25], ["Boston", 1430.00]]
print(Fore.GREEN + "Store sales" + Style.RESET_ALL)
print(tabulate(rows, headers=["City", "Sales ($)"], floatfmt=",.2f"))

Output:

Store sales
City      Sales ($)
------  -----------
Austin     1,250.50
Denver       980.25
Boston     1,430.00
colorama==0.4.6
tabulate==0.9.0

I keep two files on bigger projects: a short requirements.txt with the packages I chose, and a frozen lock file with exact versions for deploys.

Why does pip install -r requirements.txt fail?

Two errors cover most failures: a wrong file name or folder, and a version that doesn’t exist. Both stop pip before it installs anything:

tabulate==0.9.0
colorama==9.9.9

Output:

ERROR: Could not open requirements file: [Errno 2] No such file or directory: 'requirments.txt'
Requirement already satisfied: tabulate==0.9.0 in c:\pyguides\.reqenv\lib\site-packages (from -r requirements-bad.txt (line 1)) (0.9.0)
ERROR: Ignored the following yanked versions: 0.4.2
ERROR: Could not find a version that satisfies the requirement colorama==9.9.9 (from versions: 0.1, 0.1.1, 0.1.2, 0.1.3, 0.1.4, 0.1.5, 0.1.6, 0.1.7, 0.1.8, 0.1.9, 0.1.10, 0.1.11, 0.1.12, 0.1.13, 0.1.14, 0.1.15, 0.1.16, 0.1.17, 0.1.18, 0.2.0, 0.2.1, 0.2.2, 0.2.3, 0.2.4, 0.2.5, 0.2.6, 0.2.7, 0.3.0, 0.3.1, 0.3.2, 0.3.3, 0.3.4, 0.3.5, 0.3.6, 0.3.7, 0.3.8, 0.3.9, 0.4.0, 0.4.1, 0.4.3, 0.4.4, 0.4.5rc1, 0.4.5, 0.4.6rc1, 0.4.6)
ERROR: No matching distribution found for colorama==9.9.9

Error	Fix
Could not open requirements file	cd to the folder that holds the file, or pass the full path
No matching distribution found	Check the version on pypi.org or loosen the pin
Failed building wheel	Upgrade pip, or use a Python version the package supports
'pip' is not recognized	Use python -m pip or py -m pip
Installs, but ModuleNotFoundError	You installed into a different Python; activate the venv first

That last one has a full guide: ModuleNotFoundError after pip install.

Installing requirements.txt faster with uv

uv reads the same file format and installs much faster than pip. Its pip subcommand is a near drop-in replacement:

tabulate==0.9.0
colorama>=0.4.6,<0.5

Output:

Using Python 3.12.5 environment at: .reqenv
Checked 2 packages in 679ms
Using Python 3.12.5 environment at: .reqenv
Checked 3 packages in 5ms
All installed packages are compatible

I switched to uv for new projects, but plain pip is everywhere, so it’s worth knowing both. Setting up several Pythons? Here’s how to install multiple Python versions.

Useful next reads for managing projects:

• How to run a Python script
• Environment variables in Python
• Install Python on Ubuntu
• Install Python on Mac

Frequently asked questions