一、建立字典：
d = {
"name": "morra", #字典是無序的
"age": 99,
"gender": 'm'
}
a = dict()
b = dict(k1=123,k2="morra")
二、基本操作：
索引
d = {
"name": "morra",
"age": 99,
"gender": 'm'
}
print(d["name"])鍵、值、鍵值對
keys()：獲取所有鍵
values()：獲取所有值
items()：獲取所有鍵值對
d = {
"name": "morra",
"age": 99,
"gender": 'm'
}
print(d.keys())
print(type(d.keys()))
print(d.values())
print(type(d.values()))
print(d.items())
print(type(d.items()))
OUTPUT:
dict_keys(['gender', 'age', 'name'])
<class 'dict_keys'>
dict_values(['m', 99, 'morra'])
<class 'dict_values'>
dict_items([('gender', 'm'), ('age', 99), ('name', 'morra')])
<class 'dict_items'>迴圈
for a in d: #字典在for中預設只能迭代輸出key
print(a)
OUTPUT:
name
gender
age
#------------------
for i in d.keys(): #迭代輸出key
print(i)
OUTPUT:
name
gender
age
#------------------
for j in d.values(): #迭代輸出value
print(j)
OUTPUT:
morra
m
99
#------------------
for k,v in d.items(): #迭代輸出鍵值對
print(k,v)
OUTPUT:
name morra
gender m
age 99取值
實際上，在使用字典取值的時候使用最多的方法是get()而不是dict[key]，因為如果當key值不存在時，使用get()可以呼叫一個預設值，但是在dict[key]中則會報錯。
d = {
"name": "morra",
"age": 99,
"gender": 'm'
}
val1 = d.get('age')
val2 = d.get('get','123') #為key設定預設值
print(val1,val2)
OUTPUT:
99 123刪除
pop(k)：根據key值移除指定的鍵值對
d = {
"name": "morra",
"age": 99,
"gender": 'm'
}
d.pop("name")
print(d)
OUTPUT：
{'gender': 'm', 'age': 99}popitem()：從當前尾部移除鍵值對，由於字典是無序的，因此被移除的鍵值對也是隨機的。
d = {
"name": "morra",
"age": 99,
"gender": 'm'
}
d.popitem()
print(d)del：刪除指定索引的鍵值對，和pop()用法一樣
d = {
"name": "morra",
"age": 99,
"gender": 'm'
}
del d["name"]
print(d)
OUTPUT：
{'age': 99, 'gender': 'm'}判斷
用in就可以了,但是在python2.7中可以使用has_key()
批量更新
update()方法只會更新與原來不同的鍵值對：
- 如果key一樣,value不一樣，則會把原來的value覆蓋掉。
- 如果key不一樣則會把兩個鍵值對都新增進來。
- 如果有一個鍵值對的key、value和原來一樣，則不會更新。
d = {
"name": "morra",
"age": 99,
"gender": 'm'
}
d1 = {
"name": "morra",
"age1": 991,
"gender1": 'm1'
}
d.update(d1)
for k,v in d.items():
print(k,v)
OUTPUT:
name morra
age1 991
gender1 m1
gender m
age 99補充
- fromkeys()：
由於list在迭代的時候沒有隻有一個值，所以不能直接使用dict(li)把列表轉換為字典。在這裡我們需要使用字典裡的fromkeys()方法。
fromkeys() ：函式用於建立一個新字典，列表中的元素當做key，併為每個key設定一個固定值（value是可選的，如果沒有預設為None）。
seq = ("name","key")
a = dict.fromkeys(seq)
b = dict.fromkeys(seq,1)
print(a)
print(b)
OUTPUT：
{'key': None, 'name': None}
{'key': 1, 'name': 1}- @staticmethod
一般來說，要使用某個類的方法，需要先例項化一個物件再呼叫方法，或直接用類呼叫。而使用staticmethod裝飾器之後，就可以不需要例項化，直接類名.方法名()來呼叫。
這有利於組織程式碼，把某些應該屬於某個類的函式給放到那個類裡去，同時有利於名稱空間的整潔。
@staticmethod
def fromkeys(*args, **kwargs):
"""
Returns a new dict with keys from iterable and values equal to value.
"""
pass
三、原始碼
class dict(object):
"""
dict() -> new empty dictionary
dict(mapping) -> new dictionary initialized from a mapping object's
(key, value) pairs
dict(iterable) -> new dictionary initialized as if via:
d = {}
for k, v in iterable:
d[k] = v
dict(**kwargs) -> new dictionary initialized with the name=value pairs
in the keyword argument list. For example: dict(one=1, two=2)
"""
def clear(self):
"""清空字典"""
""" D.clear() -> None. Remove all items from D. """
pass
def copy(self):
""" D.copy() -> a shallow copy of D """
pass
@staticmethod # known case
def fromkeys(*args, **kwargs):
""" Returns a new dict with keys from iterable and values equal to value. """
pass
def get(self, k, d=None):
""" D.get(k[,d]) -> D[k] if k in D, else d. d defaults to None. """
pass
def items(self):
""" D.items() -> a set-like object providing a view on D's items """
pass
def keys(self):
""" D.keys() -> a set-like object providing a view on D's keys """
pass
def pop(self, k, d=None):
"""
D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
If key is not found, d is returned if given, otherwise KeyError is raised
"""
pass
def popitem(self):
"""
D.popitem() -> (k, v), remove and return some (key, value) pair as a
2-tuple; but raise KeyError if D is empty.
"""
pass
def setdefault(self, k, d=None):
""" D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D """
pass
def update(self, E=None, **F): # known special case of dict.update
"""
D.update([E, ]**F) -> None. Update D from dict/iterable E and F.
If E is present and has a .keys() method, then does: for k in E: D[k] = E[k]
If E is present and lacks a .keys() method, then does: for k, v in E: D[k] = v
In either case, this is followed by: for k in F: D[k] = F[k]
"""
pass
def values(self):
""" D.values() -> an object providing a view on D's values """
pass
def __contains__(self, *args, **kwargs):
""" True if D has a key k, else False. """
pass
def __delitem__(self, *args, **kwargs):
""" Delete self[key]. """
pass
def __eq__(self, *args, **kwargs):
""" Return self==value. """
pass
def __getattribute__(self, *args, **kwargs):
""" Return getattr(self, name). """
pass
def __getitem__(self, y):
""" x.__getitem__(y) <==> x[y] """
pass
def __ge__(self, *args, **kwargs):
""" Return self>=value. """
pass
def __gt__(self, *args, **kwargs):
""" Return self>value. """
pass
def __init__(self, seq=None, **kwargs): # known special case of dict.__init__
"""
dict() -> new empty dictionary
dict(mapping) -> new dictionary initialized from a mapping object's
(key, value) pairs
dict(iterable) -> new dictionary initialized as if via:
d = {}
for k, v in iterable:
d[k] = v
dict(**kwargs) -> new dictionary initialized with the name=value pairs
in the keyword argument list. For example: dict(one=1, two=2)
# (copied from class doc)
"""
pass
def __iter__(self, *args, **kwargs):
""" Implement iter(self). """
pass
def __len__(self, *args, **kwargs):
""" Return len(self). """
pass
def __le__(self, *args, **kwargs):
""" Return self<=value. """
pass
def __lt__(self, *args, **kwargs):
""" Return self<value. """
pass
@staticmethod # known case of __new__
def __new__(*args, **kwargs):
""" Create and return a new object. See help(type) for accurate signature. """
pass
def __ne__(self, *args, **kwargs):
""" Return self!=value. """
pass
def __repr__(self, *args, **kwargs):
""" Return repr(self). """
pass
def __setitem__(self, *args, **kwargs):
""" Set self[key] to value. """
pass
def __sizeof__(self):
""" D.__sizeof__() -> size of D in memory, in bytes """
pass
__hash__ = None