How to modify list entries during for loop?

Question

Now I know that it is not safe to modify the list during an iterative looping. However, suppose I have a list of strings, and I want to strip the strings themselves. Does re

Answer 1

The answer given by Jemshit Iskenderov and Ignacio Vazquez-Abrams is really good. It can be further illustrated with this example: imagine that

a) A list with two vectors is given to you;

b) you would like to traverse the list and reverse the order of each one of the arrays

Let's say you have

v = np.array([1, 2,3,4])
b = np.array([3,4,6])

for i in [v, b]:
    i = i[::-1]   # this command does not reverse the string

print([v,b])

You will get

[array([1, 2, 3, 4]), array([3, 4, 6])]

On the other hand, if you do

v = np.array([1, 2,3,4])
b = np.array([3,4,6])

for i in [v, b]:
   i[:] = i[::-1]   # this command reverses the string

print([v,b])

The result is

[array([4, 3, 2, 1]), array([6, 4, 3])]