why does from `from itertools import chain` works but not `import itertools.chain as chain`?

Question

Why does the following work:

from itertools import chain

but the following does not?

import itertools.chain as chain

Answer 1

The import foo.bar syntax can only be used to import a module from a package, not an object in a module. from foo import bar can be used to import a module from a package or an object from a module.