Answer by Mandera for How do I get a list of locally installed Python modules?

I'm comparing five methods to retrieve installed "modules", all of which I've seen in this thread

Summary

• pip list and working_set are for distributions, not modules.
• iter_modules and help("modules") are very similar, the biggest difference is that iter_modules doesn't include built-in.
• pip list and working_set are very similar, only difference is that working_set lowers all capital letters.
• Built-in modules are only included by help("modules") and builtin_module_names.

Related caveats

• Distributions, packages, and modules often have identical names making it easy to mistake one for the other.
• importlib.util.find_spec is for modules and is case-sensitive.
• sys.modules only lists imported modules.

Distributions

I'm saying distribution instead of package because I think it will reduce misunderstandings. A distribution/package can have multiple packages/modules inside it.

An installed distribution is not always importable by the same name. For example pip install Pillow is imported with import PIL. Sometimes a distribution even makes multiple modules importable.

Methods (Each column in order)

iter_modules

import pkgutil{module.name for module in pkgutil.iter_modules()}

help("modules") (Only prints in terminal)

help("modules")

builtin_module_names

import sysset(sys.builtin_module_names)

pip list (Only prints in terminal)

pip list in terminal

working_set

import pkg_resources{pkg.key for pkg in pkg_resources.working_set}

Conclusion

• For terminal I recommend help("modules") or python -c "help('modules')".
  • Top voted answer in this thread
• For programmatically I recommend iter_modules+builtin_module_names.
  • This answer in this thread
    • It is however very convoluted with information, see my minimal example below.

import sysimport pkgutildef get_installed_modules_names():    iter_modules = {module.name for module in pkgutil.iter_modules()}    builtin = sys.builtin_module_names    return set.union(iter_modules, builtin)