Python Dictionaries

字典（Dictionary）

字典是一个无序、可变和有索引的集合。在 Python 中，字典用花括号编写，拥有键和值。

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创建并打印字典：

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
print(thisdict)

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访问项目

您可以通过在方括号内引用其键名来访问字典的项目：

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获取 "model" 键的值：

x = thisdict["model"]

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还有一个名为 get() 的方法会给你相同的结果：

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获取 "model" 键的值：

x = thisdict.get("model")

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更改值

您可以通过引用其键名来更改特定项的值：

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把 "year" 改为 2019：

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
thisdict["year"] = 2019

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遍历字典

您可以使用 for 循环遍历字典。

循环遍历字典时，返回值是字典的键，但也有返回值的方法。

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逐个打印字典中的所有键名：

for x in thisdict:
  print(x)

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逐个打印字典中的所有值：

for x in thisdict:
  print(thisdict[x])

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您还可以使用 values() 函数返回字典的值：

for x in thisdict.values():
  print(x)

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通过使用 items() 函数遍历键和值：

for x, y in thisdict.items():
  print(x, y)

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检查键是否存在

要确定字典中是否存在指定的键，请使用 in 关键字：

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检查字典中是否存在 "model"：

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
if "model" in thisdict:
  print("Yes, 'model' is one of the keys in the thisdict dictionary")

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字典长度

要确定字典有多少项目（键值对），请使用 len() 方法。

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打印字典中的项目数：

print(len(thisdict))

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添加项目

通过使用新的索引键并为其赋值，可以将项目添加到字典中：

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thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
thisdict["color"] = "red"
print(thisdict)

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删除项目

有几种方法可以从字典中删除项目：

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pop() 方法删除具有指定键名的项：

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
thisdict.pop("model")
print(thisdict)

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popitem() Rarrabawa kawun kaiyanci na ya na baiyanci na kaiyanci (a hanyanci 3.7 kaiyanci):

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
thisdict.popitem()
print(thisdict)

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del thisdict["model"] thisdict.popitem()

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
Kalmomin na iya sauransu wani abin da ke da kalmomin:
print(thisdict)

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del thisdict["model"] del

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
Kalmomin na iya sauransu yankin gina:
del thisdict

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clear() print(thisdict) #this akan yana da rauni, saboda "thisdict" ba a samu shi ne.

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
Kalmomin na iya yin sauransu yankin gina:
print(thisdict)

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thisdict.clear()

A ka iya sauransu yankin gina Ba za ta iya sauransu ta hanyar shirin dict2 = dict1dict2 daga cikin dict1 zai iya yin sauransu, saboda dict1 wanda a yi sauransu kuma dict2 daga cikin.

Wannan na iya kasancewa wani lokaci na amfani da shiri na yankin gina: copy()。

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A amfani da copy() Yana tsara yankin gina:

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
mydict = thisdict.copy()
print(mydict)

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Wani lokaci na amfani da shiri na yankin gina domin yana tsara yankin gina shine amfani da shiri na yankin gina: dict()。

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A amfani da dict() Yana tsara yankin gina na yankin gina:

thisdict =	{
  "brand": "Porsche",
  "model": "911",
  "year": 1963
}
mydict = dict(thisdict)
print(mydict)

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Yankin gina na yankin gina

Tasirin yankin gina na iya kasancewa takwas na yankin gina, wanda a kira yankin gina na yankin gina.

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A tsara yankin gina kan takwas na yankin gina:

myfamily = {
  "child1" : {
    "name" : "Phoebe Adele",
    "year" : 2002
  },
  "child2" : {
    "name" : "Jennifer Katharine",
    "year" : 1996
  },
  "child3" : {
    "name" : "Rory John",
    "year" : 1999
  }
}

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ama idan ba ka fẹrinsa ya fi yi sauransu tare da takwas na yankin gina da suka kasance yankin gina:

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A tsara takwas na yankin gina, kuma yana tsara yankin gina kan takwas na yankin gina:

child1 = {
  "name" : "Phoebe Adele",
  "year" : 2002
}
child2 = {
  "name" : "Jennifer Katharine",
  "year" : 1996
}
child3 = {
  "name" : "Rory John",
  "year" : 1999
}
myfamily = {
  "child1" : child1,
  "child2" : child2,
  "child3" : child3
}

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dict() aikin yankin gina

An amfani da dict() Yana tsara aikin yankin gina nau'iwar dict:

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thisdict = dict(brand="Porsche", model="911", year=1963)
# Ka da farko, kalmomin na iya kasancewa kama a cikin hadadda na tsintsi
# Ka da farko, a na yi wani kuma ya fi hanyar idanin yana gudanarwa da idanin
print(thisdict)

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Dictionary Methods

Python provides a set of built-in methods that can be used on dictionaries.

Method Description
clear() Remove all elements from the dictionary
copy() Return a copy of the dictionary
fromkeys() Return a dictionary with the specified key and value
get() Return the value of the specified key
items() Return a list of tuples containing each key-value pair
keys() Return a list containing all the keys of the dictionary
pop() Remove the element with the specified key
popitem() Remove the last inserted key-value pair
setdefault() Return the value of the specified key. If the key does not exist, insert a key with the specified value.
update() Update the dictionary with the specified key-value pair
values() Return a list of all values in the dictionary