Python基础语法
===================

>>> li1.extend(li2)

>>> li.append(element)

>>> ' '.join(li)
return string

>>> str1.split(' ')
return list

>>> str1.strip()
>>> # f.readline() return a string that contains '\n'
>>> # using strip() to elimate characters that isn't need

A dict and list can be changed by passing it to a function.


Fuction Arguments
----------------------------

Default Arguments
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The default values are evaluated at the point of function definition in the defining scope.

The default value is evaluated only once. 

Dictionary As Arguments
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

::

    def foo(**args):
        print args


    def bar(a, b):
        print a, b

    d = {'a': 1, 'b': 2}

    foo(a=1, b=2) # **args means args is a dict, but it accept key word arguments
    foo(**d) # when pass a dict to arguments using **d, it unpack it to key word arguments

    bar(**d) # same as line above
    bar(a=1, b=2) # normal function can pass key word arguments too, but notice it's position

    foo(d) # error, must be key word arguments

List arguments can be the same as dictionary, 
except that it using ``*`` symbol.

Iterable
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

``for i in iterable`` works because ``iterable`` has a ``__iter__()`` function that returns 
an object that has ``next()`` function.

::
    
    elif hasattr(iterable, "__getitem__") \                                                                                           
    or hasattr(iterable, "__iter__"):

If iterable has attribute ``__getitem__``, then can use iterable[i], 
or if it attribute ``__iter__``, both case can use ``for i in iterable`` to loop.

hasattr
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

hasattr returns True if an object has public member, public function, or even static function.
But private member or private function returns false.