一般形式
for <variable> in <sequence>:
<statements>
else:
<statements>
循环list
languages = ["C", "C++", "Perl", "Python"]
for x in languages:
print (x)
range()形式
>>>for i in range(5):
... print(i)
若指定步长和区间
>>>for i in range(0, 10, 3) :
print(i)
range()与len()结合循环list（类似c循环情况）
>>>a = ['Google', 'Baidu', 'Runoob', 'Taobao', 'QQ']
>>> for i in range(len(a)):
... print(i, a[i])
冒泡排序
# python 冒泡排序
def paixu(li) :
max = 0
for ad in range(len(li) - 1):
for x in range(len(li) - 1 - ad):
if li[x] > li[x + 1]:
max = li[x]
li[x] = li[x + 1]
li[x + 1] = max
else:
max = li[x + 1]
print(li)
