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.

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))