How to copy list items to array without using for loop

Question

Let's suppose you have a python list and want to convert it to an array. The most straight forward way would be to use a for loop.

And that's what I've been doing most of the time, but it clutters the code with basic operations, and I know cython is compiled python so I wonder if there's a shorthand or more pythonic way of doing it.

list = [i for i in range(10)]

cdef int * array = <int *> malloc(sizeof(int) * 10)

cdef int i

for i in range(len(list)):
    array[i] = list[i]

Is there any syntax that allows me to perform this copy in one single line?

This doesn't seem to work:

array[:] = list[:]

Possible duplicate of How to convert python array to cython array? — ead
– ead, Commented Aug 19, 2019 at 20:18
BSO's answer stackoverflow.com/a/57562797/5769463 is also a solid advise. — ead
– ead, Commented Aug 19, 2019 at 20:19

Ben Souchet · Accepted Answer · 2019-08-19 19:24:18Z

1

I am not an expert but I think the correct way to pass a python list to a C-like array is to use the functionality of the Cython array module to copy the values to a continuous memory like this:

from cpython cimport array
import array

list = [i for i in range(10)]

cdef array.array myArray =  array.array('i', list) #we need to specify the type of the array with 'i', 'f' for float, ...

dummyFunction(myArray.data.as_ints) #this c function will receive an int *

answered Aug 19, 2019 at 19:24

Ben Souchet

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