[Tutor] Mathematical operations on a list

[Cameron Simpson]

On 20Oct2021 21:59, JUDE EJEPU <ejepujude at gmail.com> wrote:
>Sir,
>I created a function to calculate a variable G
>def gfactor(dist,electro):
>       G = pie_value() * (dist**2 - electro**2)/(2*electro)
>    return G

This is good, a function of 2 numbers.

>However, when I passed a list of arguments,:
>x = [1, 2, 3]
>y = [0.5, 0.5, 1]
>gFactor(x,y), I got an error

You're handing it lists. They are not numbers!

Please describe what result you _wanted_ to receive from this call.

I would not change the function at all.

Instead, guess at what you might want as being the equivalent of:

    [ gFactor(1, 0.5), gFactor(2, 0.5), gFactor(3, 1) ]

you would need to pair up the elements of your 2 lists and then call 
gFactor() with each pair.

_Please_ rename x and y to something else to indicate that they are 
lists and not numbers, for example "xs" and "ys", which I will use below 
to avoid confusion.

Python has a zip() builtin method to pair up lists (it will do more than 
pairs if you have more lists, BTW). So:

    paired = zip(xs, ys)

which would get you an iterable of pairs. You can then iterate over 
that:

    for x, y in paired:
        gFactor(x, y)

You probably want these as a list. You could do that like this:

    gs = []
    for x, y in paired:
        gs.append( gFactor(x, y) )

or more directly with a list comprehension:

    gs = [
        gFactor(x, y) for x, y in paired
    ]

which does the same thing.

Cheers,
Cameron Simpson <cs at cskk.id.au>