As i know we can not iterate int value while we can iterate strings in python.
I want to know exact reason why it is. ?

#Example
>>> p = 12
>>> for i in p:
...     print i
... 
Traceback (most recent call last):File "", line 1, in 
TypeError: 'int' object is not iterable
>>> p = "abctest"
>>> for i in p:
...     print i
... 
a
b
c
t
e
s
t
>>> 

Edited : I need exact reason.Please do not say that you can use range , loop.

Finally i found correct answer.

Reason:

objects which are having __iter__ they are iterable.
and we can see

>>> dir(16)
['__abs__', '__add__', '__and__', '__class__', '__cmp__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__float__', '__floordiv__', '__format__', '__getattribute__', '__getnewargs__', '__hash__', '__hex__', '__index__', '__init__', '__int__', '__invert__', '__long__', '__lshift__', '__mod__', '__mul__', '__neg__', '__new__', '__nonzero__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'imag', 'numerator', 'real']
>>> 

there is no __iter__ so int is not iterable .
We can check for other types.

hasattr(["a"], '__iter__')
True
hasattr(("a",), '__iter__')
True
hasattr(u"12", '__iter__')
False

for string there is no _iter_ so how can we say string is Iterable ??? Explanation :
string is having __getitem__

>>> dir('1')
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
>>>

We can found __getitem__ so we can say string is iterable.
The iter built-in checks for the __iter__ method and in case of strings the __getitem__ method