Reversing "group" of strings in Python -

how reverse "groups" (not list) of strings? example convert "123456789" "321654987" given "group" size equals 3.

followings code turns out print empty strings:

string = "12345678901234567890" new_string = "" in range(0, len(string), 5):     new_string = new_string + string[i:i+5:-1] print (new_string) 

thanks input , advice.

when using negative step, swap start , end values too:

new_string += string[i + 4:i - 1 if else none:-1] 

note end value excluded, , none should used include first character (-1 slice end again , string[4:-1:-1] empty).

demo:

>>> string = "12345678901234567890" >>> new_string = "" >>> in range(0, len(string), 5): ...     new_string = new_string + string[i + 4:i - 1 if else none:-1] ...  >>> new_string '54321098765432109876' 

however, may easier first slice, reverse, , save headaches of such slicings:

new_string += string[i:i + 4][::-1]