How do I reverse a sublist in a list in place?

Question

I\'m supposed to create a function, which input is a list and two numbers, the function reverses the sublist which its place is indicated by the two numbers. for example this is

Answer 1

I've conducted a tiny experiment and it seems that any assignment to list slice causes memory allocation:

import resource
resource.setrlimit(resource.RLIMIT_AS, (64 * 1024, 64 * 1024))

try:
    # Python 2
    zrange = xrange
    arr_size = 3 * 1024
except NameError:
    # Python 3
    zrange = range
    arr_size = 4 * 1024

arr = list(zrange(arr_size))

# We could allocate additional 100 integers, so there should be enough free memory
# to allocate a couple of variables for indexes in the statement below
#   additional_memory = list(zrange(100))

# MemoryError is raised here
arr[:] = zrange(arr_size)

So you have to use for loop to reverse a sublist in place.

PS: If you want to repeat this test, you should ensure that setrlimit RLIMIT_AS works fine on your platform. Also arr_size may vary for different python implementations.