What's the correct way to sort Python `import x` and `from x import y` statements?

Imports are generally sorted alphabetically and described in various places beside PEP 8.

Alphabetically sorted modules are quicker to read and searchable. After all python is all about readability. Also It is easier to verify that something is imported, and avoids duplicated imports

There is nothing available in PEP 8 regarding sorting.So its all about choice what you use.

According to few references from reputable sites and repositories also popularity, Alphabetical ordering is the way.

for eg like this:

import httplib
import logging
import random
import StringIO
import time
import unittest
from nova.api import openstack
from nova.auth import users
from nova.endpoint import cloud

OR

import a_standard
import b_standard

import a_third_party
import b_third_party

from a_soc import f
from a_soc import g
from b_soc import d

Reddit official repository also states that, In general PEP-8 import ordering should be used. However there are a few additions which is

for each imported group the order of imports should be:
import <package>.<module> style lines in alphabetical order
from <package>.<module> import <symbol> style in alphabetical order

References:

• https://code.google.com/p/soc/wiki/PythonStyleGuide
• https://github.com/reddit/reddit/wiki/PythonImportGuidelines
• http://docs.openstack.org/developer/hacking/
• http://developer.plone.org/reference_manuals/external/plone.api/contribute/conventions.html#grouping-and-sorting

PS: the isort utility automatically sorts your imports.

According to the CIA's internal coding conventions (part of the WikiLeaks Vault 7 leak), python imports should be grouped into three groups:

1. Standard library imports
2. Third-party imports
3. Application-specific imports

Imports should be ordered lexicographically within these groups, ignoring case:

import foo
from foo import bar
from foo.bar import baz
from foo.bar import Quux
from Foob import ar

The PEP 8 says nothing about it indeed. There's no convention for this point, and it doesn't mean the Python community need to define one absolutely. A choice can be better for a project but the worst for another... It's a question of preferences for this, since each solutions has pro and cons. But if you want to follow conventions, you have to respect the principal order you quoted:

1. standard library imports
2. related third party imports
3. local application/library specific imports

For example, Google recommend in this page that import should be sorted lexicographically, in each categories (standard/third parties/yours). But at Facebook, Yahoo and whatever, it's maybe another convention...