Why does from ... import appear to bind to value at import time in Python?

Question

All the Python docs I've read appear to indicate that, side-effects aside, that if you import module A and then reference A.a, you are referencing the same variable as if you wrote "from A import a".

However, that doesn't appear to be the case here and I'm not sure what's going on. I'm using Python 2.6.1.

If I create a module alpha.py:

bravo = None

def set_bravo():
  global bravo
  bravo = 1

Then create a script that imports the module:

import sys, os
sys.path.append(os.path.abspath('.'))

import alpha
from alpha import bravo

alpha.set_bravo()
print "Value of bravo is: %s" % bravo
print "Value of alpha.bravo is: %s" % alpha.bravo

Then I get this output:

Value of bravo is: None
Value of alpha.bravo is: 1

Why is that?

Answer 1

from ... import ... always binds immediately, even if a previous import only imported the module/package.

EDIT:

Contrast the following:

import alpha

alpha.set_bravo()

from alpha import bravo

print "Value of bravo is: %s" % bravo
print "Value of alpha.bravo is: %s" % alpha.bravo