Printing a string with start, stop, and step

Question

hello = "Hello there"
print(hello[10:0:-1])

This outputs:

ereht olle

And I can't figure out how or why.

print(hello[10:0:-2])

And this one outputs:

eetol

Could someone please help me to understand what the [10:0:-1] is actually doing?

Thanks!

Answer 1

The notation is in order start, stop and step. So you start at index ten, go to index zero where the endpoint is exclusive with a step of negative two, meaning backwards two. Here is a diagram of indices:

# -------------------------------------------------------------------
# |  H  |  e  |  l  |  l  |  o  |     |  t  |  h  |  e  |  r  |  e  |
# -------------------------------------------------------------------
#    X           5           4           3           2           1