Question

In Matlab I can do this:

s1 = 'abcdef'
s2 = 'uvwxyz'

s1(1:2:end) = s2(1:2:end)

s1 is now 'ubwdyf'

This is just an example of the general:

A(I) = B

Where A,B are vectors, I a vector of indices and B is the same length as I. (Im ignoring matrices for the moment).

What would be the pythonic equivalent of the general case in Python? Preferably it should also run on jython/ironpython (no numpy)

Edit: I used strings as a simple example but solutions with lists (as already posted, wow) are what I was looking for. Thanks.

Answer 1

Strings are immutable in Python, so I will use lists in my examples.

You can assign to slices like this:

a = range(5)
b = range(5, 7)
a[1::2] = b
print a

which will print

[0, 5, 2, 6, 4]

This will only work for slices with a constant increment. For the more general A[I] = B, you need to use a for loop:

for i, b in itertools.izip(I, B):
    A[i] = b