assigning itertools combinations output to a numpy array

Question

I am trying to assign the output of itertools combinations function to a numpy array and it is creating a blank array. Why does this code not work correctly?

    import numpy as np
    from itertools import combinations

    A=[10,5,7,90,4,200,64]
    B=combinations(A,5)
    NA=np.zeros([5,21],dtype=np.uint8)

    print (list(B))

    NA=list(B)
    print (NA)

B is a generator once exhausted, you can't iterrate again. list(B) will consume whole generator — Ch3steR
– Ch3steR, Commented May 26, 2020 at 20:19
B is a generator, which can be used only once. The 2nd list(B) operates on a used, empty generator. Also that first NA=... assignment does nothing for you; the 2nd overwrites it. NA = np.array(list(combinations(A,5))) is all you need. (along with some more basic Python study :) ). — hpaulj
– hpaulj, Commented May 26, 2020 at 20:20

Ehsan · Accepted Answer · 2020-05-26 20:35:46Z

1

Save the output of generator B when you exhaust it in order to use it later:

A=[10,5,7,90,4,200,64]
B=combinations(A,5)
#this is line is not really required unless you use it in between your lines here
NA=np.zeros([5,21],dtype=np.uint8)

B=list(B)
print(B)

NA=np.array(B)
print (NA)

answered May 26, 2020 at 20:35

Ehsan

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