CODEWITHSUNDEEP
pythonmatrix
fatiherdem
fatiherdem

Reputation: 1223

Python fill matrix with specific values

I have 2D matrix and I want to fill it with 0 and 1. And I have a list include some value.

For example:

values = [1, 3, 5, 8]

and I want to create this matrix

matrix = [[0, 1, 0],
          [1, 0, 1],
          [0, 0, 1]]

I made this with two nested for loop witf if statement. Values is random integers from 0 to 100. And my matrix will be 10*10. Is there any way to create this more elegant?

Upvotes: 3

Views: 32767

Answers (2)

Juan Lopes
Juan Lopes

Reputation: 10565

You can use a list compreehension:

[[1 if i*10+j in values else 0 for j in range(10)] for i in range(10)]

In this case, I suggest you to create values as a set.

values = set([1, 3, 5, 8])

Upvotes: 2

xnx
xnx

Reputation: 25528

If you can use NumPy, use fancy indexing into a flattened view of the array and reshape:

In [1]: import numpy as np

In [2]: a = np.zeros(9)

In [3]: a
Out[3]: array([ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.])

In [4]: values = [1,3,5,8]

In [5]: a[values] = 1

In [6]: a
Out[6]: array([ 0.,  1.,  0.,  1.,  0.,  1.,  0.,  0.,  1.])

In [7]: a.reshape((3,3))
Out[7]: 
array([[ 0.,  1.,  0.],
       [ 1.,  0.,  1.],
       [ 0.,  0.,  1.]])

If you want an integer array, declare a as a = np.zeros(9, dtype=int).

Upvotes: 8

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