You can't say just looking at b[:] that its creates a copy unless you know its type e.g., if `b` is a numpy array then it doesn't copy the data and by changing

You can't say just looking at b[:] that its creates a copy unless you know its type e.g., if `b` is a numpy array then it doesn't copy the data and by changing b[i] you change a[i]. list(a), copy.copy(a) are more explicit.