I have two numpy arrays:
x = np.array([-1, 0, 1, 2])
y = np.array([-2, -1, 0, 1])
Is there a way to merge these arrays together like tuples:
array = [(-1, -2), (0, -1), (1, 0), (2, 1)]
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2 Answers
In [469]: x = np.array([-1, 0, 1, 2])
In [470]: y = np.array([-2, -1, 0, 1])
join them into 2d array:
In [471]: np.array((x,y))
Out[471]:
array([[-1, 0, 1, 2],
[-2, -1, 0, 1]])
transpose that array:
In [472]: np.array((x,y)).T
Out[472]:
array([[-1, -2],
[ 0, -1],
[ 1, 0],
[ 2, 1]])
or use the standard Python zip - this treats the arrays as lists
In [474]: zip(x,y) # list(zip in py3
Out[474]: [(-1, -2), (0, -1), (1, 0), (2, 1)]
3 Comments
john k
these results are not tuple data type.
hpaulj
@johnktejik,
Out[474] is a list of tuples. Out[472] isn't, but for many purposes it is just as good - including the OP's purpose(s). When creating structured arrays the distinction between a list of tuple and a list of lists is significant, but that's an exception.
Mathi
For Python 3, zip returns an iterator instead of a list. This can be converted into a list using
list(zip(x,y))Concatenation along a second dimension may be done via np.c_[].
x = np.array([-1, 0, 1, 2])
y = np.array([-2, -1, 0, 1])
xy = np.c_[x, y]
# array([[-1, -2],
# [ 0, -1],
# [ 1, 0],
# [ 2, 1]])
If you're after an array of tuples, there's the record arrays:
xy = np.rec.fromarrays([x, y])
# rec.array([(-1, -2), ( 0, -1), ( 1, 0), ( 2, 1)], dtype=[('f0', '<i4'), ('f1', '<i4')])
# convert into a list
xy.tolist() # [(-1, -2), (0, -1), (1, 0), (2, 1)]