Python 数据类型之字典

键值对的无序集合
键和值必须成对出现
只能通过键获取值

创建字典
    创建字典和创建集合类似
    应当指定键值对而不是值
        >>> a_dict = {‘Name‘:‘Sam‘,‘Age‘:20}
        >>> a_dict
        {‘Name‘: ‘Sam‘, ‘Age‘: 20}
        >>> a_dict[‘Name‘] =  ‘zhang‘
        >>> a_dict
        {‘Name‘: ‘zhang‘, ‘Age‘: 20}
        >>> a_dict[‘Age‘]
        20
修改字典
    字典内不允许有重复的键
    键值区分大小写
    对既有字典赋值只能新值替代旧值
        >>> a_dict
        {‘Name‘: ‘zhang‘, ‘Age‘: 20}
        >>> a_dict[‘age‘] = 30
        >>> a_dict
        {‘Name‘: ‘zhang‘, ‘Age‘: 20, ‘age‘: 30}
        >>> a_dict[‘age‘] = 28
        >>> a_dict
        {‘Name‘: ‘zhang‘, ‘Age‘: 20, ‘age‘: 28}
混合值字典
    字典的值可以是任何数据类型那个
    in 判断键是否在字典中存在
        >>> a_dict = {‘old‘:[1,2,3],‘new‘:[4,5,6]}
        >>> a_dict[‘old‘]
        [1, 2, 3]
        >>> a_dict[‘old‘][2]
        3
        >>> ‘new‘ in a_dict
        True
布尔上下文环境中的字典
    空字典为假，非空字典为真

Python 数据类型之字典

原文：https://blog.51cto.com/sream/2377847