Pip freeze vs. pip list

Question

A comparison of outputs reveals differences:

user@user-VirtualBox:~$ pip list
feedparser (5.1.3)
pip (1.4.1)
setuptools (1.1.5)
wsgiref (0.1.2)
user@user-Vir         


        

Answer 1

The main difference is that the output of pip freeze can be dumped into a requirements.txt file and used later to re-construct the "frozen" environment.

In other words you can run: pip freeze > frozen-requirements.txt on one machine and then later on a different machine or on a clean environment you can do: pip install -r frozen-requirements.txt and you'll get the an identical environment with the exact same dependencies installed as you had in the original environment where you generated the frozen-requirements.txt.

Answer 2

When you are using a virtualenv, you can specify a requirements.txt file to install all the dependencies.

A typical usage:

$ pip install -r requirements.txt

The packages need to be in a specific format for pip to understand, which is

feedparser==5.1.3
wsgiref==0.1.2
django==1.4.2
...

That is the "requirements format".

Here, django==1.4.2 implies install django version 1.4.2 (even though the latest is 1.6.x). If you do not specify ==1.4.2, the latest version available would be installed.

You can read more in "Virtualenv and pip Basics", and the official "Requirements File Format" documentation.

Answer 3

To answer the second part of this question, the two packages shown in pip list but not pip freeze are setuptools (which is easy_install) and pip itself.

It looks like pip freeze just doesn't list packages that pip itself depends on. You may use the --all flag to show also those packages.

From the documentation:

--all

Do not skip these packages in the output: pip, setuptools, distribute, wheel

Answer 4

pip list shows ALL installed packages.

pip freeze shows packages YOU installed via pip (or pipenv if using that tool) command in a requirements format.

Remark below that setuptools, pip, wheel are installed when pipenv shell creates my virtual envelope. These packages were NOT installed by me using pip:

test1 % pipenv shell
Creating a virtualenv for this project…
Pipfile: /Users/terrence/Development/Python/Projects/test1/Pipfile
Using /usr/local/Cellar/pipenv/2018.11.26_3/libexec/bin/python3.8 (3.8.1) to create virtualenv…
⠹ Creating virtual environment...
<SNIP>
Installing setuptools, pip, wheel...
done.
✔ Successfully created virtual environment! 
<SNIP>

Now review & compare the output of the respective commands where I've only installed cool-lib and sampleproject (of which peppercorn is a dependency):

test1 % pip freeze       <== Packages I'VE installed w/ pip

-e git+https://github.com/gdamjan/hello-world-python-package.git@10<snip>71#egg=cool_lib
peppercorn==0.6
sampleproject==1.3.1


test1 % pip list         <== All packages, incl. ones I've NOT installed w/ pip

Package       Version Location                                                                    
------------- ------- --------------------------------------------------------------------------
cool-lib      0.1  /Users/terrence/.local/share/virtualenvs/test1-y2Zgz1D2/src/cool-lib           <== Installed w/ `pip` command
peppercorn    0.6       <== Dependency of "sampleproject"
pip           20.0.2  
sampleproject 1.3.1     <== Installed w/ `pip` command
setuptools    45.1.0  
wheel         0.34.2

Answer 5

Look at the pip documentation, which describes the functionality of both as:

pip list

List installed packages, including editables.

pip freeze

Output installed packages in requirements format.

So there are two differences:

1. Output format, freeze gives us the standard requirement format that may be used later with pip install -r to install requirements from.

2. Output content, pip list include editables which pip freeze does not.