How to keep using values from a list until the diagonal of a matrix is full using itertools












3















So I am trying to use a smaller list to populate the diagonal of a larger matrix. I thought using the cycle function in itertools would make this an easy task but I can't seem to get it to work. Here is what I tried



a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

for i in range(len(a.shape[0])):

     a[i, i] = list(itertools.cycle(b))


but this makes it endlessly iterate. I am hoping that it will stop once the diagonal has been filled. Other options that are more pythonic are greatly appreciated!






python-3.x matrix list-comprehension itertools diagonal







share|improve this question

























  • what are you trying? to set the diags to 1 then 2, then 3 etc ?

    – Patrick Artner
    Nov 19 '18 at 20:15
















3















So I am trying to use a smaller list to populate the diagonal of a larger matrix. I thought using the cycle function in itertools would make this an easy task but I can't seem to get it to work. Here is what I tried



a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

for i in range(len(a.shape[0])):

     a[i, i] = list(itertools.cycle(b))


but this makes it endlessly iterate. I am hoping that it will stop once the diagonal has been filled. Other options that are more pythonic are greatly appreciated!






python-3.x matrix list-comprehension itertools diagonal







share|improve this question

























  • what are you trying? to set the diags to 1 then 2, then 3 etc ?

    – Patrick Artner
    Nov 19 '18 at 20:15














3












3








3








So I am trying to use a smaller list to populate the diagonal of a larger matrix. I thought using the cycle function in itertools would make this an easy task but I can't seem to get it to work. Here is what I tried



a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

for i in range(len(a.shape[0])):

     a[i, i] = list(itertools.cycle(b))


but this makes it endlessly iterate. I am hoping that it will stop once the diagonal has been filled. Other options that are more pythonic are greatly appreciated!






python-3.x matrix list-comprehension itertools diagonal







share|improve this question
















So I am trying to use a smaller list to populate the diagonal of a larger matrix. I thought using the cycle function in itertools would make this an easy task but I can't seem to get it to work. Here is what I tried



a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

for i in range(len(a.shape[0])):

     a[i, i] = list(itertools.cycle(b))


but this makes it endlessly iterate. I am hoping that it will stop once the diagonal has been filled. Other options that are more pythonic are greatly appreciated!






python-3.x matrix list-comprehension itertools diagonal




python-3.x matrix list-comprehension itertools diagonal






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 19 '18 at 20:52







Amanda.py

















asked Nov 19 '18 at 20:10









Amanda.pyAmanda.py

354




354













  • what are you trying? to set the diags to 1 then 2, then 3 etc ?

    – Patrick Artner
    Nov 19 '18 at 20:15



















  • what are you trying? to set the diags to 1 then 2, then 3 etc ?

    – Patrick Artner
    Nov 19 '18 at 20:15

















what are you trying? to set the diags to 1 then 2, then 3 etc ?

– Patrick Artner
Nov 19 '18 at 20:15





what are you trying? to set the diags to 1 then 2, then 3 etc ?

– Patrick Artner
Nov 19 '18 at 20:15












1 Answer
1






active

oldest

votes


















2














you mean to use itertools.cycle, not repeat. The latter repeats the element (the list), good luck setting that into a value, specially if you force iteration (since it runs forever)



I'd create a reference on a cycle object outside the loop and assign a value to the diagonal iterating over it manually (the only proper way with cycle). Also note that your loop range was wrong. a.shape[0] is a dimension, no need for len



import numpy as np,itertools

a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

iterator = itertools.cycle(b)

for i in range(a.shape[0]):

     a[i, i] = next(iterator)


result:



>>> a

array([[ 1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  2.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  3.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  4.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  5.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  1.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  2.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  3.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  4.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  5.]])


As they loop forever, cycle and repeat should not be used in a context of forced iteration (repeat has an optional parameter to limit the repeats, though).






share|improve this answer


























  • I mean't to put cycle in my original post, oops. But my issue was that I wasn't using it as an iterator outside the loop and not using next! Thank you.

    – Amanda.py
    Nov 19 '18 at 20:25













  • those are evil "infinite loop" twins when misused :)

    – Jean-François Fabre
    Nov 19 '18 at 20:27











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









2














you mean to use itertools.cycle, not repeat. The latter repeats the element (the list), good luck setting that into a value, specially if you force iteration (since it runs forever)



I'd create a reference on a cycle object outside the loop and assign a value to the diagonal iterating over it manually (the only proper way with cycle). Also note that your loop range was wrong. a.shape[0] is a dimension, no need for len



import numpy as np,itertools

a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

iterator = itertools.cycle(b)

for i in range(a.shape[0]):

     a[i, i] = next(iterator)


result:



>>> a

array([[ 1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  2.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  3.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  4.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  5.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  1.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  2.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  3.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  4.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  5.]])


As they loop forever, cycle and repeat should not be used in a context of forced iteration (repeat has an optional parameter to limit the repeats, though).






share|improve this answer


























  • I mean't to put cycle in my original post, oops. But my issue was that I wasn't using it as an iterator outside the loop and not using next! Thank you.

    – Amanda.py
    Nov 19 '18 at 20:25













  • those are evil "infinite loop" twins when misused :)

    – Jean-François Fabre
    Nov 19 '18 at 20:27
















2














you mean to use itertools.cycle, not repeat. The latter repeats the element (the list), good luck setting that into a value, specially if you force iteration (since it runs forever)



I'd create a reference on a cycle object outside the loop and assign a value to the diagonal iterating over it manually (the only proper way with cycle). Also note that your loop range was wrong. a.shape[0] is a dimension, no need for len



import numpy as np,itertools

a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

iterator = itertools.cycle(b)

for i in range(a.shape[0]):

     a[i, i] = next(iterator)


result:



>>> a

array([[ 1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  2.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  3.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  4.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  5.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  1.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  2.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  3.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  4.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  5.]])


As they loop forever, cycle and repeat should not be used in a context of forced iteration (repeat has an optional parameter to limit the repeats, though).






share|improve this answer


























  • I mean't to put cycle in my original post, oops. But my issue was that I wasn't using it as an iterator outside the loop and not using next! Thank you.

    – Amanda.py
    Nov 19 '18 at 20:25













  • those are evil "infinite loop" twins when misused :)

    – Jean-François Fabre
    Nov 19 '18 at 20:27














2












2








2







you mean to use itertools.cycle, not repeat. The latter repeats the element (the list), good luck setting that into a value, specially if you force iteration (since it runs forever)



I'd create a reference on a cycle object outside the loop and assign a value to the diagonal iterating over it manually (the only proper way with cycle). Also note that your loop range was wrong. a.shape[0] is a dimension, no need for len



import numpy as np,itertools

a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

iterator = itertools.cycle(b)

for i in range(a.shape[0]):

     a[i, i] = next(iterator)


result:



>>> a

array([[ 1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  2.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  3.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  4.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  5.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  1.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  2.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  3.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  4.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  5.]])


As they loop forever, cycle and repeat should not be used in a context of forced iteration (repeat has an optional parameter to limit the repeats, though).






share|improve this answer















you mean to use itertools.cycle, not repeat. The latter repeats the element (the list), good luck setting that into a value, specially if you force iteration (since it runs forever)



I'd create a reference on a cycle object outside the loop and assign a value to the diagonal iterating over it manually (the only proper way with cycle). Also note that your loop range was wrong. a.shape[0] is a dimension, no need for len



import numpy as np,itertools

a = np.zeros((10,10))

b = [1, 2, 3, 4, 5]

iterator = itertools.cycle(b)

for i in range(a.shape[0]):

     a[i, i] = next(iterator)


result:



>>> a

array([[ 1.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  2.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  3.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  4.,  0.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  5.,  0.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  1.,  0.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  2.,  0.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  3.,  0.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  4.,  0.],

       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  5.]])


As they loop forever, cycle and repeat should not be used in a context of forced iteration (repeat has an optional parameter to limit the repeats, though).







share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 19 '18 at 20:28

























answered Nov 19 '18 at 20:15









Jean-François FabreJean-François Fabre

104k955112




104k955112













  • I mean't to put cycle in my original post, oops. But my issue was that I wasn't using it as an iterator outside the loop and not using next! Thank you.

    – Amanda.py
    Nov 19 '18 at 20:25













  • those are evil "infinite loop" twins when misused :)

    – Jean-François Fabre
    Nov 19 '18 at 20:27



















  • I mean't to put cycle in my original post, oops. But my issue was that I wasn't using it as an iterator outside the loop and not using next! Thank you.

    – Amanda.py
    Nov 19 '18 at 20:25













  • those are evil "infinite loop" twins when misused :)

    – Jean-François Fabre
    Nov 19 '18 at 20:27

















I mean't to put cycle in my original post, oops. But my issue was that I wasn't using it as an iterator outside the loop and not using next! Thank you.

– Amanda.py
Nov 19 '18 at 20:25







I mean't to put cycle in my original post, oops. But my issue was that I wasn't using it as an iterator outside the loop and not using next! Thank you.

– Amanda.py
Nov 19 '18 at 20:25















those are evil "infinite loop" twins when misused :)

– Jean-François Fabre
Nov 19 '18 at 20:27





those are evil "infinite loop" twins when misused :)

– Jean-François Fabre
Nov 19 '18 at 20:27




















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