Python Advanced Programming (class-level): Subclass built-in type

#-*-Coding:utf-8-*-

# python:2.x

__author__ = ' Administrator '

#类级

#在2.2, the type is presented (TYPE0 and Class) are unified (visit: Https://www.python.org/download/releases/2.2.3/descintro (may no longer exist) )-This makes the subclass of the built-in type possible, and adds a new built-in type Object

#用于所有内建类的公共祖先

#展示一个名为distinctdict类的代码, as with normal dict, but it does not allow multiple identical key values, ValueError exception occurs when the same item occurs.

Class Distincterror (Exception):

Pass

Class Distinctdict (Dict):

def __setitem__ (self, Key, value):

Try

Value_index=self.values (). Index (value)

#只要dict在2次调用之间没有发生改变

#keys () and values () will return to the corresponding list

#否则, the Dict type cannot guarantee the order of the sequence

Existing_key=self.keys () [Value_index]

If Existing_key!=key:

Raise Distincterror (' This value already exists for%s: '% (str (Self[existing_key])))

Except ValueError as S:

Pass

Super (Distinctdict,self) __setitem__ (Key,value)

My=distinctdict ()

my[' key ']= ' value '

#my [' Other_key ']= ' value ' __main__. Distincterror:this value already exists for value:

my[' Other_key ']= ' value2 '

Print my#{' other_key ': ' value2 ', ' key ': ' Value '}

#看看刚刚的代码, it will be discovered by implementing built-in types, which are like sub-types, faster and clearer

#例如

Class F (list):

def __init__ (self,a):

Self.a=a

def dir (self):

print ' f.%s '%SELF.A

For I in self:

Print I

F=f (' secret ')

Print F

F.append (' pics ')

F.append (' Apply ')

F.dir ()

#其他

"""

Starting with 2.4, the collections module has provided some useful container types that can be used to implement

1: Implement the Deque type of the double-ended queue

The 2:defaultdict type provides a dictionary-like object with default unknown key values, similar to how hash works in Prel or Ruby

----

Built-in types cover most usage scenarios

If you open create a similar sequence or map a new class, you should test its properties and observe the existing built-in types.

"""