python(or numpy) equivalent of match in R

Question

Is there any easy way in python to accomplish what the match function does in R? what match in R does is that it returns a vector of the positions of (first) matches of its first argument in its second.

For example, the following R snippet.

> a <- c(5,4,3,2,1)
> b <- c(2,3)
> match(a,b)
[1] NA NA  2  1 NA

Translate that in python, what I am looking for is a function that does the following

>>> a = [5,4,3,2,1]
>>> b = [2,3]
>>> match(a,b)
[None, None, 2, 1, None]

Thank you!

Answer 1

>>> a = [5,4,3,2,1]
>>> b = [2,3]
>>> [ b.index(x) if x in b else None for x in a ]
[None, None, 1, 0, None]

Add 1 if you really need position "one based" instead of "zero based".

>>> [ b.index(x)+1 if x in b else None for x in a ]
[None, None, 2, 1, None]

You can make this one-liner reusable if you are going to repeat it a lot:

>>> match = lambda a, b: [ b.index(x)+1 if x in b else None for x in a ]
>>> match
<function <lambda> at 0x04E77B70>
>>> match(a, b)
[None, None, 2, 1, None]