Detailed explanation of python3 dict (dictionary)

clear(clear dictionary contents)

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

#输出：None

copy(copy dictionary)

stu = {
    'num1':'Tom',
    'num2':'Lucy',
    'num3':'Sam',
}
stu2 = stu.copy()
print(stu2)

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}

get(Specify the key and get the corresponding value)

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

#输出：Lucy

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')])

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'])

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'}

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'}

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'}

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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