On 02/05/2015 16:40, Mark Lawrence wrote:
On 02/05/2015 16:26, BartC wrote:
On 30/04/2015 18:20, Ben Finney wrote:
Jon Ribbens <jon+use...@unequivocal.co.uk> writes:
If you use xrange() instead of range() then you will get an iterator
which will return each of the numbers in turn without any need to
create an enormous list of all of them.
If you use Python 3 instead of the obsolescent Python 2, the ‘range’
callable has this sensible behaviour by default.
When I first looked at Python 20 or so years ago this seemed to be the
standard way of writing a for-loop:
for i in range(N):
....
I remember being completely astonished at the time that 'range' actually
created a list of values from 0 to N-1.
I first started maybe 14 years ago and the standard way of writing a for
loop was, and still is:-
for item in items:
When did this change, or has it always been this way and you were simply
using an idiom from other languages?
Your example is the equivalent of 'forall' in other languages, where you
iterate over the values of some collection of data.
I agree that most for-loops in Pythonic code probably fall into that
category.
But for looping over a simple integer range, then using 'range' to
denote the range (and build a list as it used to do), was how it was
done. And earlier on people would have been porting coding code to
Python at which point a straightforward 'for i=a to b' loop suddenly
acquired a substantial overhead it didn't have before!
--
Bartc
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