Pyrex: step in for loop

[Luis P. Mendes]

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Hi,

I'm trying to improve speed in a module and substituted the pythonic
'for in range()' for 'for i from min < i < max:'

But, I need to define a step for the i variable. How can I do it?

for example, how do I iterate through 80000 to 140000 with step 10000?

Luis
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[Mike Meyer]

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Hi,

I'm trying to improve speed in a module and substituted the pythonic
'for in range()' for 'for i from min < i < max:'

But, I need to define a step for the i variable. How can I do it?

for example, how do I iterate through 80000 to 140000 with step 10000?

guru% pydoc range
Help on built-in function range in module __builtin__:

range(...)
range([start,] stop[, step]) -> list of integers

Return a list containing an arithmetic progression of integers.
range(i, j) returns [i, i+1, i+2, ..., j-1]; start (!) defaults to 0.
When step is given, it specifies the increment (or decrement).
For example, range(4) returns [0, 1, 2, 3]. The end point is omitted!
These are exactly the valid indices for a list of 4 elements.

so it's

for i in range(80000, 140000, 10000): ...

<mike

 

[Luis P. Mendes]

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| so it's
|
| for i in range(80000, 140000, 10000): ...
|
| <mike

For what I've read, for i in range is slower than the other for
construct used by Pyrex:

for i from iMin <= i < iMax:

My question had to do with this new expression. How can I introduce a
step there.

I am able to circumvent the problem passing a reduced range for i, let's
say iMin = 8, iMax = 14 when calling the pyrex module and then, after
the for statement:
i = i * 10000
and it works as it is intended to.


But, if there is a way to introduce the step in the 'for i from iMin <=
i < iMax:' expression, I would like to know.

Thank you for your reply.

Luis
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[Mike Meyer]

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| so it's
|
| for i in range(80000, 140000, 10000): ...
|
| <mike

For what I've read, for i in range is slower than the other for
construct used by Pyrex:

for i from iMin <= i < iMax:

My question had to do with this new expression. How can I introduce a
step there.

My bad. I missed the "Pyrex" in the subject line.

Sorry,
<mike

 

[Greg Ewing]

I'm trying to improve speed in a module and substituted the pythonic
'for in range()' for 'for i from min < i < max:'

But, I need to define a step for the i variable. How can I do it?

If you want maximum clarity, I'd suggest using the for-loop
to iterate over a contiguous range of integers and an expression
that maps the loop variable to whatever you want.

If you want the maximum possible speed, it *may* be faster
to use a while loop instead and do your own index updating.
But profile to make sure.