How can I do this function pythonic?

Question

I have a python 2D function f(x,y) that returns a number for every pair x and y. I need to calculate f(x,y) having the elements in a list x=[x0,x1,x2,x3], y=[y0,y1,y2,y3] to obtain [f(x0,y0),f(x1,y1),f(x2,y2),f(x3,y3)]. I am doing this task with a for loop

result=[]
for k in range(len(k)):
    result.append(f(x[i],y[i]))

Is there a more pythonic way to do this?if possible with numpy arrays. Many thanks

Use zip and list comprehension, is generally consider more pythonic — Dani Mesejo, Nov 17 '20 at 23:14
I would use a comprehension: `result = [f(a, b) for a, b in zip(x, y)]` — flakes, Nov 17 '20 at 23:14
Why is this tagged as `numpy`? The built-in `list`s and Numpy arrays have nothing to do with each other. — Karl Knechtel, Nov 17 '20 at 23:36
@flakes this kind of thing is exactly what `map` is built for; it implicitly zips sequences of parameters. So all you need is `result = list(map(f, x, y))`. — Karl Knechtel, Nov 17 '20 at 23:37
@KarlKnechtel huh... Today I learned! Didn't relaize it took more than two args. Thanks! — flakes, Nov 17 '20 at 23:38

score 0 · Answer 1 · answered Nov 17 '20 at 23:18

0

Using numpy is a good idea.

import numpy as np

x = np.array([0, 1, 2, 3])
y = np.array([2, 4, 6, 8])

def f(x, y):
    return x*y

z = f(x,y)
print(z) # array([ 0,  4, 12, 24])

answered Nov 17 '20 at 23:18

Nabil Daoud

221
1
10

2

Dependencies aren't free, don't use them if you can do without. I would only do this if I already had numpy in the dependencies, or if it was found to be computationally expensive without it. This would add about 10 to 15MB of bloat to your install size. – flakes Nov 17 '20 at 23:22
And several seconds to startup time, IMX. – Karl Knechtel Nov 17 '20 at 23:38

How can I do this function pythonic?

1 Answers1