python3 流程控制

表达式if ... else

>>> if 3 > 4:
...     print('False')
... else:
...     print('True')
... 
True

表达式if ... elif...else

>>> a = 10
>>> if a > 15:
...     print("ok")
... elif a < 15:
...     print("good")
... else:
...     print("what")
... 
good

循环while

while True:
...   a = input('>>>').strip()
...   b = 10
...   c = int(a)
...   if c > b:
...     print('go on')
...     continue
...   else:
...     print('ok')
...     break

循环for loop

>>> for i in range(10):
...     print('loop:',i)
... 
loop: 0
loop: 1
loop: 2
loop: 3
loop: 4
loop: 5
loop: 6
loop: 7
loop: 8
loop: 9

>>> for i in range(10):
...   if i >8:
...     break
...   print('loop:',i)
... 
loop: 0
loop: 1
loop: 2
loop: 3
loop: 4
loop: 5
loop: 6
loop: 7
loop: 8

代码优化

a = 2
b = 3
if a > b:
    c = a + b
else:
    c = a - b
print(c)
# 优化后代码量减少
a = 4
b = 5
c = a + b if a > b else a - b
print(c)

pass 、continue 和 break

# pass 跳过，本次没操作
for i in range(10):
    if i == 5:
        pass
    else:
        print('loop', i)

# continue 跳出本次循环，继续下次循环
for i in range(10):
    if i == 5:
        continue
    print('loop', i)

# break 跳出当前循环
for i in range(10):
    if i == 5:
        for j in range(10):
            print('in loop', j)
            if j == 6:
                break
        continue
    print('out loop', i)