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Why or why not?
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If you want to write code that will run on both Python 2 and Python 3, use range() as the xrange function is deprecated in Python 3. range() is faster if iterating over the same sequence multiple times. xrange() has to reconstruct the integer object every time, but range() will have real integer objects.
xrange() is more efficient because instead of generating a list of objects, it just generates one object at a time. Instead of 100 integers, and all of their overhead, and the list to put them in, you just have one integer at a time. Faster generation, better memory use, more efficient code.
range() creates a list, so if you do range(1, 10000000) it creates a list in memory with 9999999 elements. This will become an expensive operation on very large ranges. xrange() is a sequence object that evaluates lazily.
The xrange() function in Python is used to generate a sequence of numbers, similar to the range() function. However, xrange() is used only in Python 2. x whereas range() is used in Python 3. x.
For performance, especially when you're iterating over a large range, xrange() is usually better. However, there are still a few cases why you might prefer range():
In python 3, range() does what xrange() used to do and xrange() does not exist. If you want to write code that will run on both Python 2 and Python 3, you can't use xrange().
range() can actually be faster in some cases - eg. if iterating over the same sequence multiple times. xrange() has to reconstruct the integer object every time, but range() will have real integer objects. (It will always perform worse in terms of memory however)
xrange() isn't usable in all cases where a real list is needed. For instance, it doesn't support slices, or any list methods.
[Edit] There are a couple of posts mentioning how range() will be upgraded by the 2to3 tool. For the record, here's the output of running the tool on some sample usages of range() and xrange()
RefactoringTool: Skipping implicit fixer: buffer RefactoringTool: Skipping implicit fixer: idioms RefactoringTool: Skipping implicit fixer: ws_comma --- range_test.py (original) +++ range_test.py (refactored) @@ -1,7 +1,7 @@ for x in range(20): - a=range(20) + a=list(range(20)) b=list(range(20)) c=[x for x in range(20)] d=(x for x in range(20)) - e=xrange(20) + e=range(20) As you can see, when used in a for loop or comprehension, or where already wrapped with list(), range is left unchanged.
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No, they both have their uses:
Use xrange() when iterating, as it saves memory. Say:
for x in xrange(1, one_zillion): rather than:
for x in range(1, one_zillion): On the other hand, use range() if you actually want a list of numbers.
multiples_of_seven = range(7,100,7) print "Multiples of seven < 100: ", multiples_of_seven If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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