How in the world does this occur?

import_wtf.py

>>> import timeit, dis
>>> t1 = timeit.Timer("""def foo(): return pprint.pprint([])""", setup="import pprint")
>>> t2 = timeit.Timer("""def foo(): import pprint; return pprint.pprint([])""")
>>> t1.repeat()
[0.1467437744140625, 0.12576889991760254, 0.12010502815246582]
>>> t2.repeat()
[0.08302998542785645, 0.07528400421142578, 0.07703089714050293]
>>> def foo(): return pprint.pprint([])
>>> def foo2(): import pprint; return pprint.pprint([])
>>> dis.dis(foo)
  1           0 LOAD_GLOBAL              0 (pprint)
              3 LOAD_ATTR                0 (pprint)
              6 BUILD_LIST               0
              9 CALL_FUNCTION            1
             12 RETURN_VALUE        
>>> dis.dis(foo)
  1           0 LOAD_CONST               1 (-1)
              3 LOAD_CONST               0 (None)
              6 IMPORT_NAME              0 (pprint)
              9 STORE_FAST               0 (pprint)
             12 LOAD_FAST                0 (pprint)
             15 LOAD_ATTR                0 (pprint)
             18 BUILD_LIST               0
             21 CALL_FUNCTION            1
             24 RETURN_VALUE