python基础-3-字典内置方法

D.clear() -> None.  Remove all items from D.-清除字典中的所有项

>>> person = {"name":"Bob",
	      "phone":"123456",
	      "addr":"Universy Park"
	      }
>>> person
{'name': 'Bob', 'phone': '123456', 'addr': 'Universy Park'}
>>> person.clear()
>>> person
{}

D.copy() -> a shallow copy of D-copy方法返回一个具有相同键-值对的新字典(浅复制)

>>> person = {"name":["Bob","Mary","Alex"],
	      "phone":"123456",
	      "addr":"Universy Park"
	      }
>>> animal = person
>>> person
{'name': ['Bob', 'Mary', 'Alex'], 'phone': '123456', 'addr': 'Universy Park'}
>>> animal
{'name': ['Bob', 'Mary', 'Alex'], 'phone': '123456', 'addr': 'Universy Park'}
>>> animal["phone"] = "987654"
>>> animal["name"] = "lion"
>>> animal
{'name': 'lion', 'phone': '987654', 'addr': 'Universy Park'}
>>> person
{'name': 'lion', 'phone': '987654', 'addr': 'Universy Park'}

fromkeys(*args, **kwargs)-使用给定的键建立新的字典，每个键默认对应的值为None。也可以自己提供默认值。

>>> person.fromkeys(["gender","age"])
{'gender': None, 'age': None}
>>> person
{'name': 'lion', 'phone': '123', 'addr': 'Universy Park'}
>>> {}.fromkeys(["name","age"],["alex","25"])
{'name': ['alex', '25'], 'age': ['alex', '25']}
>>> {}.fromkeys(["name","age"],("alex","25"))
{'name': ('alex', '25'), 'age': ('alex', '25')}

D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None.-get方法是一个更宽松的访问字典项的方法，(直接访问字典中不存在的键时会报错，get方法不会报错)，get方法访问的键不存在时，返回None，也可利用d参数指定返回值

>>> person
{'name': 'lion', 'phone': '123', 'addr': 'Universy Park'}
>>> person.get("name")
'lion'
>>> person.get("age")
>>> person.get("age","不存在")
'不存在'

D.items() -> a set-like object providing a view on D's items-生成一个包括键-值对的可迭代对象

>>> animal = person.items()
>>> animal
dict_items([('name', 'lion'), ('phone', '123'), ('addr', 'Universy Park')])
>>> for i in person.items():
	print(i)

	
('name', 'lion')
('phone', '123')
('addr', 'Universy Park')

D.keys() -> a set-like object providing a view on D's keys-生成一个包括键的可迭代对象

>>> person
{'name': 'lion', 'phone': '123', 'addr': 'Universy Park'}
>>> person.keys()
dict_keys(['name', 'phone', 'addr'])
>>> for i in person.keys():
	print(i)

	
name
phone
addr

D.pop(k[,d]) -> v-pop方法用于获得对应于给定键的值，然后将这个键-值对从字典中移除

>>> person
{'name': 'lion', 'phone': '123', 'addr': 'Universy Park'}
>>> person.pop("name")
'lion'
>>> person
{'phone': '123', 'addr': 'Universy Park'}

D.popitem() -> (k, v)-随机弹出一个键-值对。适用于一个接一个地移除并处理项(因为不用先获取键的列表)

>>> person
{'phone': '123', 'addr': 'Universy Park'}
>>> person.popitem()
('addr', 'Universy Park')
>>> person
{'phone': '123'}

D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D-setdefault方法在某种程度上类似于get方法，能够获得与给定键相关联的值(若存在寻找的键，则返回对应的值【d参数没有作用】)，除此之外，setdefault还能在字典中不含有给定键的情况下设定相应的键值【d参数作用】

>>> person
{'phone': '123'}
>>> person.setdefault("phone","456")
'123'
>>> person.setdefault("name","lj")
'lj'
>>> person
{'phone': '123', 'name': 'lj'}

D.update([E, ]**F) -> None.  Update D from dict/iterable E and F.-利用一个字典项更新另外一个字典

>>> person
{'phone': '123', 'name': 'lj'}
>>> x = {"age":"25","genda":"boy"}
>>> person.update(x)
>>> person
{'phone': '123', 'name': 'lj', 'age': '25', 'genda': 'boy'}
>>> x
{'age': '25', 'genda': 'boy'}

D.values() -> an object providing a view on D's values-返回值的可迭代对象

>>> person
{'phone': '123', 'name': 'lj', 'age': '25', 'genda': 'boy'}
>>> person.values()
dict_values(['123', 'lj', '25', 'boy'])
>>> for i in person.values():
	print(i)

	
123
lj
25
boy

python基础-3-字典内置方法

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