from ... import OR import ... as for modules

Solution 1:

Assuming that bar is a module or package in foo, there is no difference^*, it doesn't matter. The two statements have exactly the same result:

>>> import os.path as path
>>> path
<module 'posixpath' from '/Users/mj/Development/venvs/stackoverflow-2.7/lib/python2.7/posixpath.pyc'>
>>> from os import path
>>> path
<module 'posixpath' from '/Users/mj/Development/venvs/stackoverflow-2.7/lib/python2.7/posixpath.pyc'>

If bar is not a module or package, the second form will not work; a traceback is thrown instead:

>>> import os.walk as walk
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named walk

^* In Python 3.6 and before, there was a bug with the initialization ordering of packages containing other modules, where in the loading stage of the package using import contained.module.something as alias in a submodule would fail where from contained.module import something as alias would not. See Imports in __init__.py and `import as` statement for a very illustrative example of that problem, as well as Python issues #23203 and #30024.

Solution 2:

This is a late answer, arising from what is the difference between 'import a.b as b' and 'from a import b' in python

This question has been flagged as a duplicate, but there is an important difference between the two mechanisms that has not been addressed by others.

from foo import bar imports any object called bar from namespace foo into the current namespace.

import foo.bar as bar imports an importable object (package/module/namespace) called foo.bar and gives it the alias bar.

What's the difference?

Take a directory (package) called foo which has an __init__.py containing:

# foo.__init__.py
class myclass:
    def __init__(self, var):
        self.__var = var

    def __str__(self):
        return str(self.__var)

bar = myclass(42)

Meanwhile, there is also a module in foo called bar.py.

from foo import bar
print(bar)

Gives:

42

Whereas:

import  foo.bar as bar
print(bar)

Gives:

<module 'foo.bar' from '/Users//..../foo/bar.py'>

So it can be seen that import foo.bar as bar is safer.