Require python imports to be modules

Question

The Google Style Guide for python states that one should: "Use imports for packages and modules only."

https://google.github.io/styleguide/pyguide.html#Imports

Is there a tool that flags violations of this suggestion?

Pylint does NOT do it. For example, following: Is there a tool to lint Python based on the Google style guide?

Creating a test.py the violates the guideline (exists is a function, not a module):

"""Test file for pylint"""
from os.path import exists

exists('/home')

Then, running pylint with the rc file does just fine:

$ pylint --rcfile=googlecl-pylint.rc -r n -s n  test.py
$ echo $?
0

Searching through the possible codes: http://pylint-messages.wikidot.com/all-codes, I don't see anything that looks like it would warn against this.

I have also not seen anything in pep8 or pyflakes that will catch this.

Trey

Who made Google authority on Python programming conventions? You should stick to the PEP guidelines, those are what's up. – Llanes

I am also searching for this. Any luck, @jobevers? – Thrower

@mitar: none yet. – Trey

@coldspeed FWIW, I personally like this style in my code because I find it easier to tell where all the names are coming from, and I'm a believer in readability first. Of course, it's a supplement to the conventions of PEP 8, not in conflict with it. – Africa

@Africa Note, that comment was made roughly one year before I joined the company, this post may no longer represent my views or opinions. Thanks, though! – Llanes

Looks like there is also github.com/atollk/flake8-import-restrictions now for flake8 – Stopoff

Answer 1

I made the following pylint plugin for this purpose:

import astroid
from pylint import checkers, interfaces
from pylint.checkers import utils


class ImportOnlyModulesChecked(checkers.BaseChecker):
  __implements__ = interfaces.IAstroidChecker

  name = 'import-only-modules'
  priority = -1
  msgs = {
    'W5521': (
      "Import \"%s\" from \"%s\" is not a module.",
      'import-only-modules',
      "Only modules should be imported.",
    ),
  }

  @utils.check_messages('import-only-modules')
  def visit_importfrom(self, node):
    try:
      imported_module = node.do_import_module(node.modname)
    except astroid.AstroidBuildingException:
      # Import errors should be checked elsewhere.
      return

    if node.level is None:
      modname = node.modname
    else:
      modname = '.' * node.level + node.modname

    for (name, alias) in node.names:
      # Wildcard imports should be checked elsewhere.
      if name == '*':
        continue

      try:
        imported_module.import_module(name, True)
        # Good, we could import "name" as a module relative to the "imported_module".
      except astroid.AstroidImportError:
        self.add_message(
          'import-only-modules',
          node=node,
          args=(name, modname),
        )
      except astroid.AstroidBuildingException:
        # Some other error.
        pass


def register(linter):
  linter.register_checker(ImportOnlyModulesChecked(linter))

Thrower