请教一个最简单的python问题！！

goooogo

问题：
a = [[] for x in xrange(5)]
b = [0]*5

请问a=？？？b=????

谁知道赶快帮一下忙！多谢！！！

goooogo

不是吧？问个问题，半天没有人回答！！

uumylife

>>>a
[[], [], [], [], []]
>>>b
[0, 0, 0, 0, 0]

我放在python得到的结果..
我想明白,为什么是这个结果,

goooogo

晕了。我竟然忘了直接在python中执行了。
我现在知道为什么了。
1,执行了5次。所以就生成了[[],[],[],[],[]]
2,这个是乘法的特殊用法，是相当于5 ci~!

uumylife

我再试了一下..

range   和xrange  都是得到一样的结果,他们有什么区别吗?

JarLing

我抄帮助文档的：
XRange Type

The range type is an immutable sequence which is commonly used for looping. The advantage of the range type is that an range object will always take the same amount of memory, no matter the size of the range it represents. There are no consistent performance advantages.

XRange objects have very little behavior: they only support indexing, iteration, and the len() function

我抄Python In A Nutshell的：
Returns a read-only sequence object whose items are integers in arithmetic progression. The arguments are the same as for range, covered in "range". While range creates and returns a normal list object, xrange returns a sequence object of a special type, mostly meant to be used in a for statement (you can index that object, but you cannot slice it). xrange consumes less memory than range for this specific, frequent use, in which all you need to do is loop on an arithmetic progression. However, xrange has a slightly higher overhead than range for the loop itself. Overall, performance differences between xrange and range are normally small and not worth worrying about.

JarLing

注意以下文字：

range creates and returns a normal list object, xrange returns a sequence object of a special type, mostly meant to be used in a for statement。

xrange consumes less memory than range for this specific, frequent use, in which all you need to do is loop on an arithmetic progression

Overall, performance differences between xrange and range are normally small and not worth worrying about.

happygg

也就是说,所有用到range的地方都可以用xrange代替,xrange的效率会更高些,这个理解对么?

limodou

在以后的版本中range就是使用xrange来实现的了.