6.0分支、循环、条件与枚举

while循环写法

while codition:
    pass

while codition:
    pass
else:
    pass

for循环遍历

主要是用来遍历/循环 序列或者集合、字典

for target_list in expression_list:
    pass

a=['apple','orange','banana','grape']
for x in a:
    print(x)

a=[['apple','orange','banana','grape'],(1,2,3)]
for x in a:
    for y in x:
        print(y)

for x in a:
    pass
else:
    pass

注意：只有当for循环遍历正常结束时，才会执行else后的语句。若使用break中断循环，else后的语句将不被执行

for循环计数

for x in range(0,10):
    print(x )

for x in range(0,10,2):
    print(x,end=' | ')

for x in range(10,0,-2):
    print(x,end=' | ')

for i in range(0,len(a),2):
    print(a[i],end=' | ')

a=[1,2,3,4,5,6,7,8]
b=a[0:len(a):2]
print(b)

循环中断

for x in a:
    if x==2:
        break
    print(x)

for x in a:
    if x==2:
        continue
    print(x)