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Difference between range and xrange

| January 28, 2013 | 0 Comments
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Built-in funciton Range and xrange are very different in Python. I couldn’t figure out what the difference was, and in all the code I was writing at the time, swapping one for the other made no conceivable difference.
range([start], stop[, step])
This is a versatile function to create lists containing arithmetic progressions. It is most often used in for loops. The arguments must be plain integers. If the step argument is omitted, it defaults to 1. If the start argument is omitted, it defaults to 0. The full form returns a list of plain integers [start, start + step, start + 2 * step, …]. If step is positive, the last element is the largest start + i * step less than stop; if step is negative, the last element is the smallest start + i * step greater than stop. step must not be zero (or else ValueError is raised).
Example:

>>> range(10)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(1, 11)
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> range(0, 30, 5)
[0, 5, 10, 15, 20, 25]
>>> range(0, 10, 3)
[0, 3, 6, 9]
>>> range(0, -10, -1)
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
>>> range(0)
[]
>>> range(1, 0)
[]

xrange([start], stop[, step])
This function is very similar to range(), but returns an “xrange object” instead of a list. This is an opaque sequence type which yields the same values as the corresponding list, without actually storing them all simultaneously. The advantage of xrange() over range() is minimal (since xrange() still has to create the values when asked for them) except when a very large range is used on a memory-starved machine or when all of the range’s elements are never used (such as when the loop is usually terminated with break).

CPython implementation detail: xrange() is intended to be simple and fast. Implementations may impose restrictions to achieve this. The C implementation of Python restricts all arguments to native C longs (“short” Python integers), and also requires that the number of elements fit in a native C long. If a larger range is needed, an alternate version can be crafted using the itertools module: islice(count(start, step), (stop-start+step-1+2*(step<0))//step). Difference between range and xrange: [python]>>> xrange(5) xrange(5) >>> list(xrange(5)) [0, 1, 2, 3, 4] >>> xrange(1,5) xrange(1, 5) >>> list(xrange(1,5)) [1, 2, 3, 4] >>> xrange(0,6,2) xrange(0, 6, 2) >>> list(xrange(0,6,2)) [0, 2, 4][/python] [python]a = range(0,100) print type(a) print a print a[0], a[1] [/python] result:

[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]
0 1
a = xrange(0,100) 
print type(a) 
print a 
print a[0], a[1] 

result:

<type 'xrange'>
xrange(100)
0 1
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Category: Function

About the Author ()

My name is John Link.I am 26 years old. My major is Computer science and technology. I am a junior programmer with Python.

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