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 = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
print(stu.clear())

#输出:None
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copy(copy dictionary)

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
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 = ['tom','lucy','sam']
print(dict.fromkeys(name))
print(dict.fromkeys(name,25))  #指定默认值

#输出:{'tom': None, 'lucy': None, 'sam': None}
#     {'tom': 25, 'lucy': 25, 'sam': 25}
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get(Specify the key and get the corresponding value)

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
print(stu.get('num2'))

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

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
print(stu.items())

#输出:dict_items([('num2', 'Lucy'), ('num3', 'Sam'), ('num1', 'Tom')])
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keys(get all the keys in the dictionary)

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
print(stu.keys())

#输出:dict_keys(['num3', 'num1', 'num2'])
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pop(get the value of the specified key and delete)

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
name = stu.pop('num2')
print(name,stu)

#输出:Lucy {'num1': 'Tom', 'num3': 'Sam'}
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popitem(Get a key-value pair randomly and delete it in the dictionary)

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
name = stu.popitem()
print(name,stu)

#输出:('num2', 'Lucy') {'num3': 'Sam', 'num1': 'Tom'}
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setdefault(Get the value of the specified key, if the key does not exist, create it )

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
name = stu.setdefault('num5')
print(name,stu)

#输出:None {'num1': 'Tom', 'num2': 'Lucy', 'num5': None, 'num3': 'Sam'}
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update(Add key-value pair to dictionary)

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
stu.update({'num4':'Ben'})
print(stu)

#输出:{'num2': 'Lucy', 'num3': 'Sam', 'num1': 'Tom', 'num4': 'Ben'}
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