[Python] Why is printf() giving a strange output?

I tried to use the C-function printf() in the Python command line on Linux. To make that work I imported ctypes. If I create an object of CDLL to use the printf()-function in a loop, I get a really weird output:

>>> import ctypes
>>> libc = ctypes.CDLL("libc.so.6")
>>> for i in range(10):
... libc.printf("%d", i)
...
01
11
21
31
41
51
61
71
81
91
>>>


However when I call this loop inside a function, it works as expected:

>>> import ctypes
>>> libc = ctypes.CDLL("libc.so.6")
>>> def pr():
... for i in range(10):
... libc.printf("%d", i)
... libc.printf("\n")
...
>>> pr()
0123456789
>>>


What causes this behavior? I'm using Python 2.7.6 on Linux.

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