将二维数组组合成元组

Question

I want to combine two 2d-arrays into one NX2 array, but I don't know what command should I use in python. For example, a = [1.2.3] b = [4,5,6] , and I want to have a new array which have the elements in a as the x-coordinate and b as the y-coordinate, c = [(1,4)],(2,5),(3,6)]

Any hint for this in python language?

Answer 1

You're lucky, because Python has a built-in zip function that does exactly what you want.

>>> a = [1, 2, 3]
>>> b = [4, 5, 6]
>>> zip(a, b)
[(1, 4), (2, 5), (3, 6)]

Note that in Python 3, zip returns an iterator, not a list, so you will have to use list(zip(a, b)) to get a list.

Also note that zip truncates the length of the result to the smallest list.

For example:

>>> zip([1, 2], [3, 4, 5])
[(1, 3), (2, 4)]

You can combat this with itertools.izip_longest (or itertools.zip_longest in Python 3).

>>> import itertools
>>> list(itertools.izip_longest([1, 2], [3, 4, 5], fillvalue=0))
[(1, 3), (2, 4), (0, 5)]

This will use the fillvalue to fill in the empty gaps. By default, fillvalue is set to None .

Answer 2

You can use the zip function.

    x = [1,2,3,4]
    y = [1,2,3,4]
    nodes = [zip(x,y)]

Use zip() inside list() to get the list. Or else it will print as,

[<zip object at 0x0000024AE84502C0>]

Do it i this way instead

nodes = list(zip(x,y))

It is going to print

[(1, 1), (2, 2), (3, 3), (4, 4)]