How to check if a module is installed in Python and, if not, install it within the code?

Question

I would like to install the modules 'mutagen' and 'gTTS' for my code, but I want to have it so it will install the modules on every computer that doesn't have them, but it won't try to install them if they're already installed. I currently have:

def install(package):
    pip.main(['install', package])

install('mutagen')

install('gTTS')

from gtts import gTTS
from mutagen.mp3 import MP3

However, if you already have the modules, this will just add unnecessary clutter to the start of the program whenever you open it.

Solution 1

EDIT - 2020/02/03

The pip module has updated quite a lot since the time I posted this answer. I've updated the snippet with the proper way to install a missing dependency, which is to use subprocess and pkg_resources, and not pip.

To hide the output, you can redirect the subprocess output to devnull:

import sys
import subprocess
import pkg_resources

required = {'mutagen', 'gTTS'}
installed = {pkg.key for pkg in pkg_resources.working_set}
missing = required - installed

if missing:
    python = sys.executable
    subprocess.check_call([python, '-m', 'pip', 'install', *missing], stdout=subprocess.DEVNULL)

Like @zwer mentioned, the above works, although it is not seen as a proper way of packaging your project. To look at this in better depth, read the the page How to package a Python App.

Solution 2

you can use simple try/except:

try:
    import mutagen
    print("module 'mutagen' is installed")
except ModuleNotFoundError:
    print("module 'mutagen' is not installed")
    # or
    install("mutagen") # the install function from the question

Solution 3

If you want to know if a package is installed, you can check it in your terminal using the following command:

pip list | grep <module_name_you_want_to_check>

How this works:

pip list

lists all modules installed in your Python.

The vertical bar | is commonly referred to as a "pipe". It is used to pipe one command into another. That is, it directs the output from the first command into the input for the second command.

grep <module_name_you_want_to_check>

finds the keyword from the list.

Example:

pip list| grep quant

Lists all packages which start with "quant" (for example "quantstrats"). If you do not have any output, this means the library is not installed.

Solution 4

You can check if a package is installed using pkg_resources.get_distribution:

import pkg_resources

for package in ['mutagen', 'gTTS']:
    try:
        dist = pkg_resources.get_distribution(package)
        print('{} ({}) is installed'.format(dist.key, dist.version))
    except pkg_resources.DistributionNotFound:
        print('{} is NOT installed'.format(package))

Note: You should not be directly importing the pip module as it is an unsupported use-case of the pip command.

The recommended way of using pip from your program is to execute it using subprocess:

subprocess.check_call([sys.executable, '-m', 'pip', 'install', 'my_package'])

Solution 5

Although @girrafish's answer might suffice, you can check package installation via importlib too:

import importlib

packages = ['mutagen', 'gTTS']
[subprocess.check_call(['pip', 'install', pkg]) 
for pkg in packages if not importlib.util.find_spec(pkg)]

View more solutions

Comments

[Foxes]

This works very well, but it gives the output of "requirement already satisfied", adding unnecessary clutter to the start of the code when you open it. Is there anyway to make it so it doesn't echo the "requirement already satisfied"?

[zwer]

Please add a disclaimer that a kitten dies whenever somebody uses import pip in their code as a workaround for proper packaging. -_-

[Girrafish]

@Gameskiller01 I added the code for what you're looking for, although it is not my code. Please look at the link as I have no credit for that.

[Foxes]

@TheGirrafish, I found that exact code as well in my searches about 5 minutes ago. XD Thanks anyway.

[aoh]

pip.get_installed_distributions() returns type EggInfoDistribution, so I think if you want to use the line if package not in pip.get_installed_distributions(): you either change it to str(pip.get_installed_distributions()) or something else that allows us to make that comparison

[Girrafish]

@aoh Not sure what you mean, pip.get_installed_distributions() returns type list?

[aoh]

@TheGirrafish Sorry, I meant that the list is comprised of "EggInfoDistribution" (and also DistINfoDistribution") which are part of the pip library. For example in my case, the first item in the list is "xmltodict 0.10.2", but "xmltodict 0.10.2" in pip.get_installed_distributions() returns False while "xmltodict 0.10.2" in str(pip.get_installed_distributions()) returns True

[Girrafish]

@aoh Ohh, yes I see what you mean now, I edited the answer :)

[Josh Correia]

As of pip 10.0.0 you must use import pip._internal and pip._internal.main

[live2]

please add some sescription and not only a code block

[dcoles]

Please don't import or use any functions from pip. It is not a supported use-case and may break at any time: github.com/pypa/pip/issues/5243

[Girrafish]

@dcoles Thanks for bringing this up, I've changed the code snippet to use subprocess over pip.

[dcoles]

Also rather than using than redirecting sys.stdout, I'd recommend just using subprocess.check_call(args, stdout=subprocess.DEVNULL) to ignore pip's stdout.

[andjelx]

Faced with issue that e.g. prompt_toolkit module name returned by pkg_resources.working_set() as prompt-toolkit

[papiro]

This is totally not the answer because the question is asking how to install as well, and do it all of this from code...

[matan h]

I think the question mean that the Python code will install modules on every computer runs it

[My Work]

How does this handles versions? Does it update the package to the latest release if it is installed? Does it install the latest version? Can it be specified?

[aschultz]

"start with" should technically be "contains" ... grep "\wquant" or grep "^quant" would be more accurate. On Windows I also need grep -E for extended regexes.

[Prox]

[subprocess.check_call([sys.executable, '-m', 'pip', 'install', pkg, '-q']) for pkg in ['datasets'] if not importlib.util.find_spec(pkg)] sys.executable should use the python executable, also added -q for quiet, in case it prints. Great and short answer.