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  • python学习-19 字典

    字典dict

    1.dic = {key:value,key:value}

    字典有{ }括住,字典的value可以是任意值,字典的key的值不包括列表和字典

    di = {"age":18,"name":"john","a":True,"b":[1,2,"movie"],"c":(1,2,"ff",)}
    print(di)

    运算结果:

    {'age': 18, 'name': 'john', 'a': True, 'b': [1, 2, 'movie'], 'c': (1, 2, 'ff')}
    
    Process finished with exit code 0

    2.取值(只能通过索引的方式,不能用切片的方式。因为字典是无序的)

    di = {"age":18,"name":"john","a":True,"b":[1,2,"movie"],"c":(1,2,"ff",)}
    v = di["c"][0]
    print(v)

    运行结果:

    1
    
    Process finished with exit code 0

    3.删除

    di = {"age":18,"name":"john","a":True,"b":[1,2,"movie"],"c":(1,2,"ff",)}
    del di["b"][2]
    print(di)

    运行结果:

    {'age': 18, 'name': 'john', 'a': True, 'b': [1, 2], 'c': (1, 2, 'ff')}
    
    Process finished with exit code 0

    4.循环(只能用for循环,不能用while,因为字典是无序的)

    di = {"age":18,"name":"john","a":True,"b":[1,2,"movie"],"c":(1,2,"ff",)}
    for k,v in di.items():
     print(k,v)

    运行结果:

    age 18
    name john
    a True
    b [1, 2, 'movie']
    c (1, 2, 'ff')
    
    Process finished with exit code 0

    5.方法

    -根据序列创建字典并指定统一的值

    a= dict.fromkeys(["age",123,"465"],222)
    print(a)

    运行结果:

    {'age': 222, 123: 222, '465': 222}
    
    Process finished with exit code 0

    -根据key取值,如果没有key,则为none

    dic = {"a":1,"b":3}
    v = dic.get("a")
    print(v)

    运行结果:

    1
    
    Process finished with exit code 0

    -删除

    dic = {"a":1,"b":3}
    v = dic.pop("a")
    print(v)
    print(dic)

    运行结果:

    1
    {'b': 3}
    
    Process finished with exit code 0

    -随机删除

    dic = {"a":1,"b":3}
    v = dic.popitem()
    print("删除的值为:",v)
    print(dic)

    运行结果:

    删除的值为: ('b', 3)
    {'a': 1}
    
    Process finished with exit code 0

    -设置,如果设置的值不存在,则创建新的,如果存在,不设置,直接获取当前的值

    dic = {"a":1,"b":3}
    v = dic.setdefault("c",132)
    print(v)
    print(dic)

    运行结果:

    132
    {'a': 1, 'b': 3, 'c': 132}
    
    Process finished with exit code 0

    -添加

    第一种方法:

    dic = {"a":1,"b":3}
    v = dic.update({"c":"456"})
    print(dic)

    运行结果:

    {'a': 1, 'b': 3, 'c': '456'}
    
    Process finished with exit code 0

    第二种方法:

    dic = {"a":1,"b":3}
    v = dic.update(c=123,d=456)
    print(dic)

    运行结果:

    {'a': 1, 'b': 3, 'c': 123, 'd': 456}
    
    Process finished with exit code 0
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  • 原文地址:https://www.cnblogs.com/liujinjing521/p/11107070.html
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