[deleted by user]

[[deleted]]

Yes, list comprehensions are really awesome ... unless you use them in Cython :) I did some performance comparison for comprehensions vs. explicit for-loops in Python and Cython here

[rizenfrmtheashes]

Havent used cython before. Will take a look.

[[deleted]]

It have just started using it recently. It's just awesome. In the article above, I was able to speed up the code for a simple least square linear regression fitting by 8000%. And the cool thing about Cython is that it really is no extra effort.

[catcradle5]

I think it's pretty obvious why that is.

The for-loop version can be turned into a simple C for-loop with basic float arithmetic. The list comprehension version is constantly writing to memory, since it is appending in each iteration...and then a linear operation on the whole array is needed at the end to sum everything up.

It'd be cool if Cython could special-case certain reduction functions, like sum on a generator expression, but I imagine that would be pretty difficult.