I use this command

EDIT: Thanks Addisson Klinke for suggestion

pip freeze -r requirements.txt | grep -B100 "pip freeze" | grep -v "pip freeze"

pip freeze -r requirements.txt | sed '/freeze/,$ d'

When I ran pip freeze -r requirements.txt the output is something like

APScheduler==3.2.0
Eve==0.6.4
Eve-Elastic==0.3.8
## The following requirements were added by pip freeze:
arrow==0.8.0
Cerberus==0.9.2

I have a requirements file like this

APScheduler
Eve
Eve-Elastic

So I get this output and sed to remove the dependencies that I don`t want.

First output this to a file

pip freeze -q -r requirements.txt | sed '/freeze/,$ d' > requirements-froze.txt

That will output just the libs with version

APScheduler==3.2.0
Eve==0.6.4
Eve-Elastic==0.3.8

Then replace requirements file

mv requirements-froze.txt requirements.txt

pipreqs can save the day for a specific project. Just

pip install pipreqs
#then
pipreqs path/to/project

Github Page

I have tried both pipreqs and pigar and found pigar is better because it also generates information about where it is used, it also has more options.

if you are using linux then do it with sed

pip freeze | sed 's/==.*$/''/' > requirements.txt

Here is a simplified version based on the previous comment: https://stackoverflow.com/a/40026169/4052041

mv requirements.txt requirements.txt.bak
pip freeze -q -r requirements.txt.bak | awk '/.*pip freeze.*/  {exit} {print}' > requirements.txt

I had the same issue with pip freeze. In my case the problem was that I ran pip freeze without activating my projects virtual environment. I activated the virtual environment and pip freeze > requirements.txt worked fine.

So do make sure you activate your projects virtual environment by running <virtualenv folder name>\Scipts\activate on Windows or source <virtualenv folder name>\bin\activate on Linux.

If the virtualenv has global access you should run pip freeze with the -l or --local option, pip freeze -l which according to the pip freeze docs

-l, --local
If in a virtualenv that has global access, do not output globally-installed packages.

I just had the same issue, here's what I've found to solve the problem.

First create the venv in the directory of your project, then activate it.

For Linux/MacOS : python3 -m venv ./venv source myvenv/bin/activate

For Windows : python3 -m venv .\venv env\Scripts\activate.bat

Now pip freeze > requirements.txt should only takes the library used in the project.

NB: If you have already begin your project you will have to reinstall all the library to have them in pip freeze.

pip install pipreqs,
pipreqs>requirements.txt

That works easily

I still suggest using the official pip freeze > requirements.txt (documentation) compared to the two alternative features using pigar and pipreqs mentioned in the other answers because pip freeze lists the effective package names.

Incomplete comparison among the three as per February 2022

(1) There can be a mismatch between module and package name such as my-package (package name) vs my_package (module name).

(2) There can be several packages using the same top level folder such as my-package1 and my-package2 (package names) which are installed under my/package1 and my/package2, which are imported by Python's command import my.package1 and import my.package2. Note that pipreqs notes version 0.0.0 for the not existing package my.

I know these are very particular cases but I hope giving people this overview can help understanding limitations and avoid possible mistakes.

I do came across same situation. After activating the virtual enviroment and doing

pip3 freeze > requirements.txt

still its collect all package install on my WSL ubuntu 22.04

After install "pipreqs" and typing pipreqs>requirments.txt My Wsl got stuck.

The best solution is pip3 freeze -l > requirments.txt its only collected my local package used for my development.

With your virtualenv activated, do python -E -m pip freeze. The -E flag means, according to python --help, ignore PYTHON* environment variables (such as PYTHONPATH), so pip it's not going to access to global site-packages.