for循环 字符串

strs = "abcdefg"
# 循环字符串，会将字符串中每个字符循环一遍
for s in strs:
    print(s)

for 循环list，tuple，set

lists = ["books","names","helloworld"]
for l in lists:
    print(l)

lists = ("books","names","helloworld")
for l in lists:
    print(l)

lists = {"books","names","helloworld","books"}
for l in lists:
    print(l)

for 循环dict

user_info = {
    "name":"xiaowang",
    "age":30,
    "salary": 25000,
    "spending": 10000,
    "friends": ["xiaozhang","xiaowang","laowang"],
    "hobby": [
        {"name":"reading","year":8},
        {"name":"game","year":20},
        {"name":"sport","year":10}
    ]
}
for key,val in user_info.items():
    print(f'{key}--{val}')

字典数据类型是键值对的方式，循环的时候需要获取到字典key 和value。

user_info = {
    "name":"xiaowang",
    "age":30,
    "salary": 25000,
    "spending": 10000,
    "friends": ["xiaozhang","xiaowang","laowang"],
    "hobby": [
        {"name":"reading","year":8},
        {"name":"game","year":20},
        {"name":"sport","year":10}
    ]
}
for key,val in user_info.items():
    print(f'{key}--{val}')
    # == 表示判断 判断两个值是否相等 如果key的值为 friends
    if key == "friends":
        # 对val 进行循环 当if 条件成立的时候才会执行下面的for循环语句
        for name in val:
            print(f"name的值为：{name}")

练习

针对如下json格式数据进行循环。

user_info = {
    "name":"xiaowang",
    "age":30,
    "salary": 25000,
    "spending": 10000,
    "friends": ["xiaozhang","xiaowang","laowang"],
    "hobby": [
        {"name":"reading","year":8},
        {"name":"game","year":20},
        {"name":"sport","year":10}
    ]
}

如果 key的值为 ‘hobby’, 对hobby的值进行再次循环。

for key,val in user_info.items():
    print(f'{key}--{val}')
    # == 表示判断 判断两个值是否相等 如果key的值为 friends
    if key == "hobby":
        # 针对hobby值中的list列表进行循环
        for hobby in val:
            # list中的每个字典 {'name': 'reading', 'year': 8}
            print(f"hobby is {hobby}")
            for k,v in hobby.items():
                print(f'{k}---{v}')