Detailed explanation of python3 dict (dictionary)-Python Tutorial-php.cn

Detailed explanation of python3 dict (dictionary)

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Release： 2017-03-25 13:14:37

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clear(clear dictionary contents)

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
print(stu.clear())

#输出：None

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copy(copy dictionary)

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
stu2 = stu.copy()
print(stu2)

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fromkeys( Specify a list and use the values in the list as the keys of the dictionary to generate a dictionary)

name = [&#39;tom&#39;,&#39;lucy&#39;,&#39;sam&#39;]
print(dict.fromkeys(name))
print(dict.fromkeys(name,25))  #指定默认值

#输出：{&#39;tom&#39;: None, &#39;lucy&#39;: None, &#39;sam&#39;: None}
#     {&#39;tom&#39;: 25, &#39;lucy&#39;: 25, &#39;sam&#39;: 25}

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get(Specify the key and get the corresponding value)

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
print(stu.get(&#39;num2&#39;))

#输出：Lucy

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items(Return the key-value pair A list that makes up the element ")

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
print(stu.items())

#输出：dict_items([(&#39;num2&#39;, &#39;Lucy&#39;), (&#39;num3&#39;, &#39;Sam&#39;), (&#39;num1&#39;, &#39;Tom&#39;)])

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keys(get all the keys in the dictionary)

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
print(stu.keys())

#输出：dict_keys([&#39;num3&#39;, &#39;num1&#39;, &#39;num2&#39;])

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pop(get the value of the specified key and delete)

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
name = stu.pop(&#39;num2&#39;)
print(name,stu)

#输出：Lucy {&#39;num1&#39;: &#39;Tom&#39;, &#39;num3&#39;: &#39;Sam&#39;}

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popitem(Get a key-value pair randomly and delete it in the dictionary)

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
name = stu.popitem()
print(name,stu)

#输出：(&#39;num2&#39;, &#39;Lucy&#39;) {&#39;num3&#39;: &#39;Sam&#39;, &#39;num1&#39;: &#39;Tom&#39;}

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setdefault(Get the value of the specified key, if the key does not exist, create it )

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
name = stu.setdefault(&#39;num5&#39;)
print(name,stu)

#输出：None {&#39;num1&#39;: &#39;Tom&#39;, &#39;num2&#39;: &#39;Lucy&#39;, &#39;num5&#39;: None, &#39;num3&#39;: &#39;Sam&#39;}

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update(Add key-value pair to dictionary)

stu = {
    &#39;num1&#39;:&#39;Tom&#39;,
    &#39;num2&#39;:&#39;Lucy&#39;,
    &#39;num3&#39;:&#39;Sam&#39;,
}
stu.update({&#39;num4&#39;:&#39;Ben&#39;})
print(stu)

#输出：{&#39;num2&#39;: &#39;Lucy&#39;, &#39;num3&#39;: &#39;Sam&#39;, &#39;num1&#39;: &#39;Tom&#39;, &#39;num4&#39;: &#39;Ben&#39;}

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