Detailed explanation of how to use dict dictionary in python3-Python Tutorial-php.cn

Detailed explanation of how to use dict dictionary in python3

高洛峰

Release： 2017-03-24 16:32:48

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This article mainly introduces how to use dict (dictionary) in python3. The article gives a detailed list of functions, which has certain reference value for everyone. Friends who need it can take a look below.

1. clear (clear the 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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2. copy (copy the 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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3. fromkeys (specify a list, use the values in the list as the keys of the dictionary, and 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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4. get (specify key, 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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5. items (returns a list of "elements composed of key-value pairs")

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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6. 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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7. pop (get the value of the specified key 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.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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8. popitem (randomly obtain a key-value pair 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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9. 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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10. 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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