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读取和拷贝

if __name__ == '__main__':
    print()
    dictInfo = {1: "This is one", 2: "", 3: '', 5: "This is five"}
    # 字典的读取
    assert (len(dictInfo[1]) > 0)
    assert (len(dictInfo[2]) <= 0)
    assert (len(dictInfo[3]) <= 0)
    if 4 in dictInfo:
        assert (len(dictInfo[4]) <= 0)
    else:
        print("4 is not in dictInfo")

    # 字典的引用拷贝
    # (1) 直接赋值，对象的引用（别名）
    dic1 = {"Name": "HaiCoder", "Age": 100, "Score": 99.5}
    dic2 = dic1
    dic2["Name"] = "Demo"
    print("dic1", json.dumps(dic1))
    print("dic2", json.dumps(dic2))
    # print(json.dumps(dic1, sort_keys=True, indent=4, separators=(',', ':')))

    # (2) copy函数 拷贝父对象，不会拷贝对象的内部的子对象，数组也是个引用
    dic1 = {"Name": "HaiCoder", "Age": 100, "Score": 99.5, "phone": [10086, 10010]}
    dic2 = dic1.copy()
    dic2["Name"] = "Demo"
    print("dic1", json.dumps(dic1))
    print("dic2", json.dumps(dic2))
    dic1["phone"].append(10000)
    dic2["phone"].append(20000)
    print("dic1", json.dumps(dic1))
    print("dic2", json.dumps(dic2))

    # (3) copy.deepcopy， 完全拷贝了父对象及其子对象
    dic1 = {"Name": "HaiCoder", "Age": 100, "Score": 99.5, "phone": [10086, 10010]}
    dic2 = copy.deepcopy(dic1)
    dic2["Name"] = "Demo"
    print("dic1", json.dumps(dic1))
    print("dic2", json.dumps(dic2))
    dic1["phone"].append(10000)
    dic2["phone"].append(20000)
    print("dic1", json.dumps(dic1))
    print("dic2", json.dumps(dic2))
    
    #(4) copy.copy 浅拷贝
    a = [1, 2, 3, 4, ['a', 'b']]  # 原始对象
    b = a  # 赋值，传对象的引用
    c = copy.copy(a)  # 对象拷贝，浅拷贝
    d = copy.deepcopy(a)  # 对象拷贝，深拷贝
    a.append(5)  # 修改对象a
    a[4].append('c')  # 修改对象a中的['a', 'b']数组对象
    print('a = ', a) # [1, 2, 3, 4, ['a', 'b', 'c'], 5]
    print('b = ', b) # [1, 2, 3, 4, ['a', 'b', 'c'], 5]
    print('c = ', c) # [1, 2, 3, 4, ['a', 'b', '4'], 5]
    print('d = ', d) # [1, 2, 3, 4, ['a', 'b']]

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创建和类型

if __name__ == '__main__':
    print()
    # {} 创建字典详解
    dic = {"Name": "HaiCoder", "Age": 100, "Score": 99.5}
    print(dic)
    print(type(dic))  # 使用 type() 函数，获取字典类型

    # 使用 fromkeys()
    # dictName = dict.fromkeys(list，value=None), list 参数表示字典中所有键的列表，value 参数默认为 None，表示所有键对应的值
    keys = ("Name", "Age", "Score")
    dic = dict.fromkeys(keys)
    print(dic)
    dic["Name"] = 1
    dic["Age"] = "2"
    dic["Score"] = [1, "2"]
    dic["Phone"] = {10086, 10010}
    print(dic)
    print(type(dic["Score"]), type(dic["Phone"]))  # Score是list，Phone是set

    # 使用 dict() 创建字典详解
    # dic = dict(one=1, two=2, three=3) # 用这种方式创建字典的 key 不需要加双引号
    dic = dict(Monday=1, Tuesday=2, Wednesday=3, Thursday=4, Friday=5)
    print(dic)

访问和遍历

if __name__ == '__main__':
    print()
    dic = {"Name": "HaiCoder", "Age": 100, "Score": 99.5}
    # (1)使用key作为下标访问，如果键不存在，程序会抛出异常
    print(dic["Name"])
    # (2)使用 get() 方法访问，如果键不存在，程序会不会抛出异常，而是返回一个空值，同时该方法可以设置键不存在时，使用的默认值。
    print(dic.get("Name"), dic.get("name", "nil"), dic.get("name"))
    if dic.get("name") is None:
        print("name not in dic")
    # (3)使用 items() 访问，返回是一个 key 对应一个 value 的元祖的列表的形式
    print(dic.items())

    # (4)使用 keys() 访问，返回的是字典的所有的key list
    print(dic.keys())
    # (5)使用 values() 访问，返回的是字典的所有的val list
    print(dic.values())

    # 遍历
    print("------(1)遍历key------")
    for key in dic:
        print(key)

    print("------(2)遍历key------")
    for key in dic.keys():  # for key in a和 for key in a.keys() 完全等价
        print(key)

    print("------(3)遍历val------")
    for value in dic.values():
        print(value)

    print("------(4)遍历k-v------")
    for kv in dic.items():
        print(kv, kv[0], kv[1])

    # 为啥这里的key和value必须是string
    dic = {"Name": "HaiCoder", "Age": "100", "Score": "99.5"}
    print("------遍历k-v------")
    for (key, value) in dic.items():
        print(key + ':' + value)
    for key, value in dic.items():
        print(key + ':' + value)

删除和弹出

if __name__ == '__main__':
    print()
    # 删除单个元素、删除整个元素
    dic = {"Name": "HaiCoder", "Age": 100, "Score": 99.5}
    # del dic["Phone"] 报错
    del dic["Name"]
    print("dic", dic)
    del dic
    # print("dic", dic) 报错

    # 弹出一个元素
    # 使用 pop 从字典中弹出不存在的元素
    dic = {"Name": "HaiCoder", "Age": 100, "Score": 99.5}
    # print("dic Before pop name", dic)
    # item = dic.pop("name") 报错
    # print("name =", item, "dic After pop name =", dic)
    print("dic Before pop Name", dic)
    item = dic.pop("Name")
    print("Name =", item, "dic After pop Name =", dic)

    dic = {"Name": "HaiCoder"}
    print("dic Before pop Name", dic)
    item = dic.pop("Name")
    print("Name =", item, "dic After pop Name =", dic)  # {}
    
    # 使用 popitem 从字典中随机返回一个元素
    dic = {"Name": "HaiCoder", "Age": 100, "Score": 99.5}
    print("dic before popitem =", dic)
    item = dic.popitem()
    print("Pop Item =", item, "dic after popitem =", dic)
    # 从空字典中弹出元素，程序报错
    # dic = {}
    # item = dic.popitem() 报错
    # print("Pop Item =", item, "dic after popitem =", dic)

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