共同点：

两者都用于循环

for i in range(0, 100):
    print i

for i in xrange(0, 100):
    print i

不同点：

1. range会直接生成一个list对象
2. xrange不直接生成List，而是在访问的时候再生成相应的值，类似Java中的Iterator + LazyLoad

范例：

>>> a = range(0,100)
>>> print a
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]
>>> a = xrange(0,100)
>>> print a
xrange(100)
>>> print a[1]
1
>>> print a[19]
19