3、分支循环

1、if

   if <条件判断1>:

     <执行1>

elif <条件判断2>:

     <执行2>

elif <条件判断3>:

     <执行3>

else:

     <执行4>

2、for

sum = 0

for x in range(101):

    sum = sum + x

print(sum)

3、while

sum = 0

n = 99

while n > 0:

    sum = sum + n

    n = n - 2

print(sum)