CODEWITHSUNDEEP
python
ksprong
ksprong

Reputation: 333

Index into list in multiple places in Python?

Say I have two lists A which has 10 elements, and I want to assign the list B = [x1, y1] to values in A. If the values are sequential, it is straightforward e.g. A[1:3] = B. But what if my indices are non-sequential? In MATLAB I can do A([3 10]) = B;, is there an equivalently clean Python solution? The for loop to do this is straightforward, but I am wondering if I am missing something more "Pythonic".

Upvotes: 0

Views: 75

Answers (2)

spencerlyon2
spencerlyon2

Reputation: 9676

Whenever I try to emulate some Matlab functionality in Python I use numpy. Using a numpy array instead of a python list allows to you get the functionality you are looking for with almost the same syntax as Matlab:

In [1]: import numpy as np

In [2]: a = np.arange(10)

In [3]: b = [200, 300]

In [4]: a[[2, 9]] = b

In [5]: a
Out[5]: array([  0,   1, 200,   3,   4,   5,   6,   7,   8, 300])

Upvotes: 2

Sean Vieira
Sean Vieira

Reputation: 159915

Slightly more verbose, but you can use tuple unpacking to assign to new indices:

>>> x = range(1, 11)
>>> x[3], x[7] = 99, 999
>>> x
[1, 2, 3, 99, 5, 6, 7, 999, 9, 10]

Upvotes: 3

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