How to Check the Versions of Python Modules

How do I check the versions of Python modules?

Use pip instead of easy_install.

With pip, list all installed packages and their versions via:

pip freeze

On most Linux systems, you can pipe this to grep (or findstr on Windows) to find the row for the particular package you're interested in.

---

Linux:

pip freeze | grep lxml

lxml==2.3

Windows:

pip freeze | findstr lxml

lxml==2.3

---

For an individual module, you can try the __version__ attribute. However, there are modules without it:

python -c "import requests; print(requests.__version__)"
2.14.2

python -c "import lxml; print(lxml.__version__)"

Traceback (most recent call last):

File "<string>", line 1, in <module>

AttributeError: 'module' object has no attribute 'version'

Lastly, as the commands in your question are prefixed with sudo, it appears you're installing to the global python environment. I strongly advise to take look into Python virtual environment managers, for example virtualenvwrapper.

Python and pip, list all versions of a package that's available?

(update: As of March 2020, many people have reported that yolk, installed via pip install yolk3k, only returns latest version. Chris's answer seems to have the most upvotes and worked for me)

The script at pastebin does work. However it's not very convenient if you're working with multiple environments/hosts because you will have to copy/create it every time.

A better all-around solution would be to use yolk3k, which is available to install with pip. E.g. to see what versions of Django are available:

$ pip install yolk3k
$ yolk -V django
Django 1.3
Django 1.2.5
Django 1.2.4
Django 1.2.3
Django 1.2.2
Django 1.2.1
Django 1.2
Django 1.1.4
Django 1.1.3
Django 1.1.2
Django 1.0.4

yolk3k is a fork of the original yolk which ceased development in 2012. Though yolk is no longer maintained (as indicated in comments below), yolk3k appears to be and supports Python 3.

Note: I am not involved in the development of yolk3k. If something doesn't seem to work as it should, leaving a comment here should not make much difference. Use the yolk3k issue tracker instead and consider submitting a fix, if possible.

Find which version of package is installed with pip

As of pip 1.3, there is a pip show command.

$ pip show Jinja2
---
Name: Jinja2
Version: 2.7.3
Location: /path/to/virtualenv/lib/python2.7/site-packages
Requires: markupsafe

In older versions, pip freeze and grep should do the job nicely.

$ pip freeze | grep Jinja2
Jinja2==2.7.3

How do I get a python module's version number through code?

Generalized answer from Matt's, do a dir(YOURMODULE) and look for __version__, VERSION, or version. Most modules like __version__ but I think numpy uses version.version

Checking a Python module version at runtime

I'd stay away from hashing. The version of libxslt being used might contain some type of patch that doesn't effect your use of it.

As an alternative, I'd like to suggest that you don't check at run time (don't know if that's a hard requirement or not). For the python stuff I write that has external dependencies (3rd party libraries), I write a script that users can run to check their python install to see if the appropriate versions of modules are installed.

For the modules that don't have a defined 'version' attribute, you can inspect the interfaces it contains (classes and methods) and see if they match the interface they expect. Then in the actual code that you're working on, assume that the 3rd party modules have the interface you expect.

How to know what python version a package is compatible with

You can look up the package on the Python Package Index and scroll down to the "Meta" section in the left sidebar. This shows the Python version required by the package. As you do not specify the package you are looking for, I will use numpy as an example. For the current version of numpy, the following information is listed:

Requires: Python >=3.7

Therefore, you need Python 3.7 or higher to install this version of numpy.

If you are using an older version of Python and need the most recent version of the package that is compatible with that version, you can go to the release history (the second link at the top of the sidebar) and try different versions, scrolling down to the "Meta" section for every version. This is still a manual process, but less work than trying to install every single version.

Note: often, support for older versions is dropped in larger updates (so when either the first or second version number is updated), so you can skip small updates to speed up your search process.

For example, using this process, you can deduce that numpy 1.19.5 is the latest version to support Python 3.6, and numpy 1.16.6 is the latest version to support Python 2.7. At the top of the page, the command to install an older version of a package is shown, for example: pip install numpy==1.16.6.

How do I get a list of locally installed Python modules?

Solution

Do not use with pip > 10.0!

My 50 cents for getting a pip freeze-like list from a Python script:

import pip
installed_packages = pip.get_installed_distributions()
installed_packages_list = sorted(["%s==%s" % (i.key, i.version)
     for i in installed_packages])
print(installed_packages_list)

As a (too long) one liner:

sorted(["%s==%s" % (i.key, i.version) for i in pip.get_installed_distributions()])

Giving:

['behave==1.2.4', 'enum34==1.0', 'flask==0.10.1', 'itsdangerous==0.24', 
 'jinja2==2.7.2', 'jsonschema==2.3.0', 'markupsafe==0.23', 'nose==1.3.3', 
 'parse-type==0.3.4', 'parse==1.6.4', 'prettytable==0.7.2', 'requests==2.3.0',
 'six==1.6.1', 'vioozer-metadata==0.1', 'vioozer-users-server==0.1', 
 'werkzeug==0.9.4']

Scope

This solution applies to the system scope or to a virtual environment scope, and covers packages installed by setuptools, pip and (god forbid) easy_install.

My use case

I added the result of this call to my flask server, so when I call it with http://example.com/exampleServer/environment I get the list of packages installed on the server's virtualenv. It makes debugging a whole lot easier.

Caveats

I have noticed a strange behaviour of this technique - when the Python interpreter is invoked in the same directory as a setup.py file, it does not list the package installed by setup.py.

Steps to reproduce:

Create a virtual environment

$ cd /tmp
$ virtualenv test_env
New python executable in test_env/bin/python
Installing setuptools, pip...done.
$ source test_env/bin/activate
(test_env) $ 

Clone a git repo with setup.py

(test_env) $ git clone https://github.com/behave/behave.git
Cloning into 'behave'...
remote: Reusing existing pack: 4350, done.
remote: Total 4350 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (4350/4350), 1.85 MiB | 418.00 KiB/s, done.
Resolving deltas: 100% (2388/2388), done.
Checking connectivity... done.

We have behave's setup.py in /tmp/behave:

(test_env) $ ls /tmp/behave/setup.py
/tmp/behave/setup.py

Install the python package from the git repo

(test_env) $ cd /tmp/behave && pip install . 
running install
...
Installed /private/tmp/test_env/lib/python2.7/site-packages/enum34-1.0-py2.7.egg
Finished processing dependencies for behave==1.2.5a1

If we run the aforementioned solution from /tmp

>>> import pip
>>> sorted(["%s==%s" % (i.key, i.version) for i in pip.get_installed_distributions()])
['behave==1.2.5a1', 'enum34==1.0', 'parse-type==0.3.4', 'parse==1.6.4', 'six==1.6.1']
>>> import os
>>> os.getcwd()
'/private/tmp'

If we run the aforementioned solution from /tmp/behave

>>> import pip
>>> sorted(["%s==%s" % (i.key, i.version) for i in pip.get_installed_distributions()])
['enum34==1.0', 'parse-type==0.3.4', 'parse==1.6.4', 'six==1.6.1']
>>> import os
>>> os.getcwd()
'/private/tmp/behave'

behave==1.2.5a1 is missing from the second example, because the working directory contains behave's setup.py file.

I could not find any reference to this issue in the documentation. Perhaps I shall open a bug for it.

How can I check all the installed Python versions on Windows?

I just got the answer. By typing "py -h" or "py --help" I got the help message:

C:\Users\admin>py -h
Python Launcher for Windows Version 3.7.1150.1013

usage:
py [launcher-args] [python-args] script [script-args]

Launcher arguments:

-2     : Launch the latest Python 2.x version
-3     : Launch the latest Python 3.x version
-X.Y   : Launch the specified Python version
     The above all default to 64 bit if a matching 64 bit python is present.
-X.Y-32: Launch the specified 32bit Python version
-X-32  : Launch the latest 32bit Python X version
-X.Y-64: Launch the specified 64bit Python version
-X-64  : Launch the latest 64bit Python X version
-0  --list       : List the available pythons
-0p --list-paths : List with paths

Which tells me that "-0" (zero, not letter "O") lists the available pythons:

C:\Users\admin>py -0
Installed Pythons found by py Launcher for Windows
 -3.7-64 *
 -3.7-32
 -2.7-64
 -2.7-32

While "-0p" lists not only the versions, but also the paths:

C:\Users\admin>py -0p
Installed Pythons found by py Launcher for Windows
 -3.7-64        C:\Users\admin\AppData\Local\Programs\Python\Python37\python.exe *
 -3.7-32        C:\Users\admin\AppData\Local\Programs\Python\Python37-32\python.exe
 -2.7-64        C:\Python27_64\python.exe
 -2.7-32        C:\Python27_32\python.exe

How to list all installed packages and their versions in Python?

If you have pip install and you want to see what packages have been installed with your installer tools you can simply call this:

pip freeze

It will also include version numbers for the installed packages.

Update

pip has been updated to also produce the same output as pip freeze by calling:

pip list

Note

The output from pip list is formatted differently, so if you have some shell script that parses the output (maybe to grab the version number) of freeze and want to change your script to call list, you'll need to change your parsing code.

How to check if all packages meet version requirements?

You can do something like this and define the modules and versions in a dictionary:

import pkg_resources

module_versions = {"absl-py":"0.1.10", "agate":"1.6.0"}

for module, v_req in module_versions.items():
    try:
        if pkg_resources.get_distribution(module).version != v_req:
            print(f"{module}, Required Version: {v_req}, Your Version: {v_inst}")
    except:
        print(f"{module} not installed")

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