What's the difference between xrange() and range() in Python2

We all kown Python2 have two Built-in function which are range and xrange,they are both use in for looping.

Similarities

1. They are both use in forloop
2. They are both built-in function in Python2
3. They all accept 3 arguments [start,stop,step],start is default 0,step is default 1,and if stop is bigger than start,it will return a Empty list.

>>> x=range(0,10,1)  
>>> x  
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]  

Differences

• range will be built a list immediately if it is generated,but the xrange is gerenate a object like this

>>>t=xrange(10)  
>>>t  
xrange(10)  
>>>type(t)  
<type 'xrange'>  

so xrange is use less memory and it has faster processing speed if the loop is especially large.And gerenates the numbers in the range on demand.

So it has not a slice becaus of it is a object not list

t[:]

Traceback (most recent call last):  
  File "<pyshell#11>", line 1, in <module>  
    t[:]
TypeError: sequence index must be integer, not 'slice'

The implementation method of range has been removed in Python3,but xrange’s is keeped,Python3 is remove the xrange name. So range() is more power in Python3.

Official document

Help on class xrange in module builtin:

class xrange(object)
| xrange(stop) -> xrange object
| xrange(start, stop[, step]) -> xrange object
|
| Like range(), but instead of returning a list, returns an object that
| generates the numbers in the range on demand. For looping, this is
| slightly faster than range() and more memory efficient.