python学习笔记 流程控制语句

流程控制语句

if语句

a = 6
if a > 4:
    print("ok")
else:
    print("no")

ok

# if in
numbers_1 = [1,2,3,4]
a = 3
if a in numbers_1:
    print("in")
else:
    print("out")

in

# if in and
numbers_2 = [1,3,5,7]
numbers_3 = [2,4,6,8]
a = 3
b = 6
if a in numbers_2 and b in numbers_2:
    print("a and b in numbers_2")
else:
    print("no in")

if a in numbers_2 and b in numbers_3:
    print("a in numbers_2 and b in numbers_3")
else:
    print("no in ")

no in
a in numbers_2 and b in numbers_3

# if any 切片中的任意一个数满足条件
if any(x >3 for x in numbers_2):
    print("ok")
else:
    print("no")

ok

# if all 前片中的所有书都满足条件
if all(x >3 for x in numbers_2):
    print("ok")
else:
    print("no")

no

for循环

# 遍历range生成的序列
for x in range(5):
    print(x,end="")

01234

# 遍历列表 切片
for x in [1,2,3]:
    print(x,end="")

123

# 遍历元组
for x in (1,2,3):
    print(x,end="")

123

# 遍历字典
my_dict = {"name":"duyong","age":20}
for key in my_dict:
    print(key)
for key in my_dict.keys():
    print(key)
for value in my_dict.values():
    print(value)
for key,value in my_dict.items():
    print(f"{key}:{value}")

name
age
name
age
duyong
20
name:duyong
age:20

# for else 只有循环全部执行完才会执行else 中间退出不执行else
for x in [1,2,3]:
    print(x)
else:
    print("end")

1
2
3
end

for x in [1,2,3]:
    if x == 2:
        break
    print(x)
else:
    print("end")

1

for x in [1,2,3]:
    if x ==2:
        continue
    print(x)
else:
    print("end")

1
3
end

# for 遍历枚举类型 
for index,x in enumerate(['a','b','c','d']):
    print(f"{index}->{x}")

0->a
1->b
2->c
3->d

while 循环

# 普通用法
a = 3
while a>0:
    print(a)
    a-=1

3
2
1

# while 循环中的输入阻塞
while True:
    name = input("name(q退出):")
    if name == "q":
        break
    else:
        print(name)

name(q退出):dd
dd
name(q退出):a
a
name(q退出):q

# while 中的eles
i = 0
while i<6:
    print(i)
    i+=1
else:
    print("over")

0
1
2
3
4
5
over