Python3笔记013 - 3.4 循环语句

第3章 流程控制语句

• 3.1 程序结构
• 3.2 选择语句
• 3.3 条件表达式
• 3.4 循环语句
• 3.5 跳转语句
• 3.6 空语句

3.4 循环语句

1、while 循环

# 带else的while循环，循环结束后执行，根据需要取舍else
while 条件表达式：
    循环体
else:
    语句

a = 0
while a <= 5:
    print(a)
    a += 1
else:
    print("循环已结束")

说明：python中没有do...while语句

2、for 循环

# 常用的循环模式
for 迭代变量 in 对象：
    循环体

# 带else的循环模式，循环结束后执行
for 迭代变量 in 对象：
    循环体
else:
    语句

# 从列表中按顺序一个一个地取出值
list1 = ["Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"]
for wday in list1:
    print(wday)
# 从字典中取出键、值、键值对
dict1 = {"Monday":"星期一","Tuesday":"星期二","wednesday":"星期三","Thursday":"星期四","Friday":"星期五","Saturday":"星期六","Sunday":"星期日",}
for key in dict1.keys():
    print(key)
for value in dict1.values():
    print(value)
for item in dict1.items():
    print(item)
# 利用range()创建列表
list1 = []
for i in range(3):
    list1.append(i)
print(list1)