how best to iterate i times ?

[Randall Smith]

In the case I know how may times I want to iterate, one way to do it is
like this:

for i in range(100000):
dothis()

I like how clean this syntax is, but this method is very wasteful. The
list created by range(100000) consumes a fair amount of memory and it is
only used to iterate.

This uses less memory:

i = 0
while i <= 100000:
dothis()
i = i + 1
del i

The problem with the while loop is that it is ugly. I have to introduce
a new variable i, and assign a new value every time I loop. Also, any
links I may have to i, say (y = i) will break when I reassign with (i =
i + 1) rather than y continuing to = i.

Example
i = 0
y = i
while i <= 100000:
dothis()
i = i + 1

print i # i == 100001
print y # y == 0

There are times when I need to know the state of an 'iterator'.

So, question is: What is the efficient, elegant, pythonic way to
iterate with integers?

Randall

[Patrick Useldinger]

On Wed, 17 Mar 2004 19:07:36 GMT, Randall Smith <ra*****@tnr.cc > wrote:

In the case I know how may times I want to iterate, one way to do it is
like this:

for i in range(100000):
dothis()

I believe that xrange does the same without using much memory.
--
http://www.homepages.lu/pu/

[Peter Otten]

Randall Smith wrote:

So, question is: What is the efficient, elegant, pythonic way to
iterate with integers?

The standard way is to use xrange() instead of range(). If you are
interested only in the repetition, not the numbers, you can also use
itertools.repea t(). Let's see what is fastest:

(1)
for i in xrange(N):
pass

(2)
for _ in repeat(None, N):
pass

$ timeit.py "for i in xrange(100000): pass"
100 loops, best of 3: 1.09e+04 usec per loop
$ timeit.py -s"from itertools import repeat" "for i in repeat(None, 100000):
pass"
100 loops, best of 3: 5.73e+03 usec per loop
Peter

[Mike Rovner]

Randall Smith wrote:

for i in range(100000):
dothis()

I like how clean this syntax is, but this method is very wasteful.
The list created by range(100000) consumes a fair amount of memory
and it is only used to iterate. .... So, question is: What is the efficient, elegant, pythonic way to
iterate with integers?

Solely for that purpose 'xrange' was created:

for i in xrange(100000):
dothis()

HTH,
Mike

[Randall Smith]

Thank you all.

You were all very helpful.
Randall

Mike Rovner wrote:

Randall Smith wrote:

for i in range(100000):
dothis()

I like how clean this syntax is, but this method is very wasteful.
The list created by range(100000) consumes a fair amount of memory
and it is only used to iterate.

...

So, question is: What is the efficient, elegant, pythonic way to
iterate with integers?

Solely for that purpose 'xrange' was created:

for i in xrange(100000):
dothis()

HTH,
Mike