python - How do I repeatedly shift and pad elements in a list to get a list of lists? -

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i have list a = [1, 2, 3, ..., n] , want repeatedly shift list list of lists. first row should a, second row [2, 3, 4, ...], third row [3, 4, 5, ...], until last row [n, 0, 0, ...]. missing elements in last columns should zeros. trying put them individually, n >= 100 manually padding zeros take long. how do this?

edit same question numpy arrays, have.

>>> = [1, 2, 3, 4] >>> [ a[i:] + i*[0] in range(len(a))] [[1, 2, 3, 4], [2, 3, 4, 0], [3, 4, 0, 0], [4, 0, 0, 0]]

how works

to i'th shifted list, can use: a[i:] + i*[0]. list comprehension repeatedly i's need.

using numpy

+ means different numpy arrays normal python lists. consequently, above code needs tweaks adapt numpy:

>>> import numpy np >>> = np.arange(1, 5) >>> [ np.concatenate((a[i:], np.zeros(i))) in range(len(a))] [array([1, 2, 3, 4]),  array([2, 3, 4, 0]),  array([3, 4, 0, 0]),  array([4, 0, 0, 0])]

if want final result numpy array:

 >>> np.array([np.concatenate((a[i:], np.zeros(i))) in range(len(a)) ]) array([[ 1.,  2.,  3.,  4.],        [ 2.,  3.,  4.,  0.],        [ 3.,  4.,  0.,  0.],        [ 4.,  0.,  0.,  0.]])

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