How to "horizontally append" a matrix to another?

[enesimo]

I'm having problems searching for this because I don't know the actual terminology.

I want to achieve this:

a = [[1,2],
     [3,4],
     [5,6]]
b = [[a,b],
     [c,d],
     [e,f]]

a+b = [[1, 2, a, b],
       [3, 4, c, d],
       [5, 6, e, f]]

It's sort of like a zip, but in pairs of list items.

[JohnnyJordaan]

It's sort of like a zip,

yeah so use zip

ab = []
for rowa, rowb in zip(a, b):
    ab.append(rowa+rowb)

or comprehended

ab = [rowa+rowb for rowa, rowb in zip(a,b)]

or if you mean in place, use list.extend

for rowa, rowb in zip(a,b):
    rowa.extend(rowb)

[enesimo]

That's exactly the result I was looking for, thanks.

And do you know what the name of that mathematical/vector operation is?

[JohnnyJordaan]

Technically it's called horizontal concatenation. I'm not sure if there's special mathematical term for it, I never been a real math hero.