Python Native Datatypes -- dictionary

>>>  d  =  { " server " : " mpilgrim " ,  " database " : " master " }
>>>  d
{ ' server ' :  ' mpilgrim ' ,  ' database ' :  ' master ' }
>>>  d[ " server " ]
' mpilgrim '
>>>  d[ " database " ]
' master '
>>>  d[ " mpilgrim " ]
Traceback (innermost last):
  File  " <interactive input> " , line  1 ,  in  ?
KeyError: mpilgrim

 

1、每一个dictionary中的每一个item就是一对值：key-value。可以通过key引用value，但不能通过value引用key。
2、每一个key是大小写敏感的
3、给一个dictionary添加一个新item：dictName[newKey] = newValue。如果newKey存在，则newValue会覆盖原来的value。这也表明添加、修改item用的是相同的语法。
4、value的类型可以是任意的，同一个dictionary中的value的类型并不需要一致。key的类型必须是所有不可变的类型，tuple有时也可以作为key，这时候tuple不能包含可变类型，不管是直接包含还是间接包含。
5、del D[k]删除一个key是k的item。
6、操作 k in D 可以用来检查key k 是否包含在D的所有keys中
7

Dictionary object methods

Method

Description

Nonmutating methods

D .copy( )

Returns a shallow copy of the dictionary (a copy whose items are the same objects as D 's, not copies thereof)

D .has_key( k )

Returns TRue if k is a key in D ; otherwise, returns False , just like k in D

D .items( )

Returns a new list with all items (key/value pairs) in D

D .keys( )

Returns a new list with all keys in D

D .values( )

Returns a new list with all values in D

D .iteritems( )

Returns an iterator on all items (key/value pairs) in D

D .iterkeys( )

Returns an iterator on all keys in D

D .itervalues( )

Returns an iterator on all values in D

D .get( k [, x ])

Returns D [ k ] if k is a key in D ; otherwise, returns x (or None , if x is not given)

Mutating methods

D .clear( )

Removes all items from D , leaving D empty

D .update( D1 )

For each k in D1 , sets D [ k ] equal to D1 [ k ]

D .setdefault( k [, x ])

Returns D [ k ] if k is a key in D ; otherwise, sets D [ k ] equal to x and returns x

D .pop( k [, x ])

Removes and returns D [ k ] if k is a key in D ; otherwise, returns x (or raises an exception if x is not given)

D .popitem( )

Removes and returns an arbitrary item (key/value pair)