How to get an array from the results of an iteration

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07-05-2021 09:58 PM
mlopezr95984
New Contributor III

Hello,

I am trying to generate an array out of the results of this iteration. 

import numpy as np

num=3

for x in range(num+1):

      a=np.array([2,x])

      print(a)

Result:
[2 0] [2 1] [2 2] [2 3]

So, I would like to have an array

a = [2 0 2 1 2 2 2 3]

I have not figured out how to apply a np.concatenate as it does not allow me to assign a variable to each result.

Any ideas?

Thank you!

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1 Solution

Accepted Solutions
DanPatterson
MVP Esteemed Contributor

 

 

num=3
lst =[]
for x in range(num+1):
      lst.append([2, x])
out = np.array(lst)
out
Out[4]: 
array([[2, 0],
       [2, 1],
       [2, 2],
       [2, 3]])
out.ravel()
Out[5]: array([2, 0, 2, 1, 2, 2, 2, 3])

 

 

better

 

 

num=3
lst =[]
for x in range(num+1):
      lst.extend([2, x])
out = np.array(lst)
out
Out[7]: array([2, 0, 2, 1, 2, 2, 2, 3])

 

better

skip iteration all together

 

num = 4
val = 2
a = np.empty(shape=(num, 2), dtype=np.int32)
a.fill(val)
a[:, 1] = np.arange(num)
a
array([[2, 0],
       [2, 1],
       [2, 2],
       [2, 3]])
a.ravel()
array([2, 0, 2, 1, 2, 2, 2, 3])

 

 

There are more efficient ways.

Also note, create the final array at the end


... sort of retired...

View solution in original post

2 Replies
DanPatterson
MVP Esteemed Contributor

 

 

num=3
lst =[]
for x in range(num+1):
      lst.append([2, x])
out = np.array(lst)
out
Out[4]: 
array([[2, 0],
       [2, 1],
       [2, 2],
       [2, 3]])
out.ravel()
Out[5]: array([2, 0, 2, 1, 2, 2, 2, 3])

 

 

better

 

 

num=3
lst =[]
for x in range(num+1):
      lst.extend([2, x])
out = np.array(lst)
out
Out[7]: array([2, 0, 2, 1, 2, 2, 2, 3])

 

better

skip iteration all together

 

num = 4
val = 2
a = np.empty(shape=(num, 2), dtype=np.int32)
a.fill(val)
a[:, 1] = np.arange(num)
a
array([[2, 0],
       [2, 1],
       [2, 2],
       [2, 3]])
a.ravel()
array([2, 0, 2, 1, 2, 2, 2, 3])

 

 

There are more efficient ways.

Also note, create the final array at the end


... sort of retired...
mlopezr95984
New Contributor III

Thank you Dan! 

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