When I do a pip freeze I see large number of Python packages that I didn’t explicitly install, e.g.

$ pip freeze
Cheetah==2.4.3
GnuPGInterface==0.3.2
Landscape-Client==11.01
M2Crypto==0.20.1
PAM==0.4.2
PIL==1.1.7
PyYAML==3.09
Twisted-Core==10.2.0
Twisted-Web==10.2.0
(etc.)

Is there a way for me to determine why pip installed these particular dependent packages? In other words, how do I determine the parent package that had these packages as dependencies?

For example, I might want to use Twisted and I don’t want to depend on a package until I know more about not accidentally uninstalling it or upgrading it.

You could try pipdeptree which displays dependencies as a tree structure e.g.:

$ pipdeptree
Lookupy==0.1
wsgiref==0.1.2
argparse==1.2.1
psycopg2==2.5.2
Flask-Script==0.6.6
  - Flask [installed: 0.10.1]
    - Werkzeug [required: >=0.7, installed: 0.9.4]
    - Jinja2 [required: >=2.4, installed: 2.7.2]
      - MarkupSafe [installed: 0.18]
    - itsdangerous [required: >=0.21, installed: 0.23]
alembic==0.6.2
  - SQLAlchemy [required: >=0.7.3, installed: 0.9.1]
  - Mako [installed: 0.9.1]
    - MarkupSafe [required: >=0.9.2, installed: 0.18]
ipython==2.0.0
slugify==0.0.1
redis==2.9.1

To get it run:

pip install pipdeptree

EDIT: as noted by @Esteban in the comments you can also list the tree in reverse with -r or for a single package with -p <package_name> so to find what installed Werkzeug you could run:

$ pipdeptree -r -p Werkzeug
Werkzeug==0.11.15
  - Flask==0.12 [requires: Werkzeug>=0.7]

The pip show command will show what packages are required for the specified package (note that the specified package must already be installed):

$ pip show specloud

Package: specloud
Version: 0.4.4
Requires:
nose
figleaf
pinocchio

pip show was introduced in pip version 1.4rc5

As I recently said on a hn thread, I’ll recommend the following:

Have a commented requirements.txt file with your main dependencies:

## this is needed for whatever reason
package1

Install your dependencies: pip install -r requirements.txt. Now you get the full list of your dependencies with pip freeze -r requirements.txt:

## this is needed for whatever reason
package1==1.2.3

## The following requirements were added by pip --freeze:
package1-dependency1==1.2.3
package1-dependency1==1.2.3

This allows you to keep your file structure with comments, nicely separating your dependencies from the dependencies of your dependencies. This way you’ll have a much nicer time the day you need to remove one of them :)

Note the following:

• You can have a clean requirements.raw with version control to rebuild your full requirements.txt.
• Beware of git urls being replaced by egg names in the process.
• The dependencies of your dependencies are still alphabetically sorted so you don’t directly know which one was required by which package but at this point you don’t really need it.
• Use pip install --no-install <package_name> to list specific requirements.
• Use virtualenv if you don’t.

You may also use a one line command which pipes the packages in requirements to pip show.

cut -d'=' -f1 requirements.txt | xargs pip show

First of all pip freeze displays all currently installed packages Python, not necessarily using PIP.

Secondly Python packages do contain the information about dependent packages as well as required versions. You can see the dependencies of particular pkg using the methods described here. When you’re upgrading a package the installer script like PIP will handle the upgrade of dependencies for you.

To solve updating of packages i recommend using PIP requirements files. You can define what packages and versions you need, and install them at once using pip install.

Use pipupgrade!

$ pip install pipupgrade
$ pipupgrade --format tree --all --check

pipupgrade displays a dependency graph and highlights each package for a possible update (based on semantic versioning). It also displays conflicting child dependencies in a pretty way. pipupgrade also ensures to upgrade packages present within multiple Python environments. Compatible with Python2.7+, Python3.4+ and pip9+, pip10+, pip18+, pip19+.

(workaround, not true answer)

Had the same problem, with lxml not installing and me wanting to know who needed lxml. Not who lxml needed. Ended up bypassing the issue by.

1. noting where my site packages were being put.

2. go there and recursive grep for the import (the last grep’s –invert-match serves to remove lxml’s own files from consideration).

Yes, not an answer as to how to use pip to do it, but I didn’t get any success out of the suggestions here, for whatever reason.

 site-packages me$ egrep -i --include=*.py  -r -n lxml . | grep import | grep --invert-match /lxml/

I wrote a quick script to solve this problem. The following script will display the parent (dependant) package(s) for any given package. This way you can be sure it is safe to upgrade or install any particular package. It can be used as follows: dependants.py PACKAGENAME

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

"""Find dependants of a Python package"""

import logging
import pip
import pkg_resources
import sys

__program__ = 'dependants.py'


def get_dependants(target_name):
    for package in pip._internal.utils.misc.get_installed_distributions():
        for requirement_package in package.requires():
            requirement_name = requirement_package.project_name
            if requirement_name == target_name:
                yield package.project_name


# configure logging
logging.basicConfig(format='%(levelname)s: %(message)s',
                    level=logging.INFO)

try:
    target_name = sys.argv[1]
except IndexError:
    logging.error('missing package name')
    sys.exit(1)

try:
    pkg_resources.get_distribution(target_name)
except pkg_resources.DistributionNotFound:
    logging.error("'%s' is not a valid package", target_name)
    sys.exit(1)

print(list(get_dependants(target_name)))