codecademy笔记，二维list

animals = []
for i in range(5):
animals.append(["O" * 5 ])

print animals[0][0]

choices = ['pizza', 'pasta', 'salad', 'nachos']

print 'Your choices are:'
for index, item in enumerate(choices):
print index + 1, item

range有负数的用法：str反向输出,str转换成list

def reverse(text):
length_of_text = len(text)
length_of_text -= 1
text_list = list(text)
stuff = []
for n in range(length_of_text,-1,-1):
stuff.append(text_list
)
answer = "".join(stuff)
return answer

range(5,-1,-1) #[5,4,3,2,1]
结合range和list的用法，能索引list的index
text_list[5],text_list[4],...实现了
将字符串转化为list，然后反向输出的功能。