格式：

for 变量 in 列表:

while 表达式：


一、for循环

#!/usr/bin/python

#for [0..5]
sum = 0; #当我没有初始化sum时，会提示TypeError: unsupported operand type(s) for +:

#'builtin_function_or_method' and 'int'

for x in [0, 1, 2, 3, 4, 5]:
sum = sum + x;
print x, sum;
print sum;


#for [0..5]
sum = 0;
for x in range(6):
sum += x;
print x, sum;
print sum;


#for list/tuple
list = ['a', 'b', 'c', 'you'];
for list in list:
print list;


二、while循环

#!/usr/bin/python

n = 9
while n > 0:
print n;
n -= 1; #python不支持 ++/--操作