Understanding - Advanced, exercise 19

Text

The variable the variable my_family_name contains the strings of a a family name. The variable my_mat_number contains the string of a matriculation number of ten digits (e.g. "0000123456"). Study the execution of the following function when it is called as follows: f(my_family_name, my_mat_number).

def f(last_name, mat):
   d = {}
   i = -1
   for c in last_name:
       if c not in d:
           i = i + 1
           d[i] = c

   if len(d) > 0:
       for n in mat:
           i = int(n) % len(d)
           return d[i] + f(last_name[1:], mat[1:])

   return "$"

Hints

The function f is a recursive function organised in two blocks. The second block contains the recursive step, while the if len(d) > 0 statement hides the basic case of the recursion when the condition is False.

Additional material

The runnable Python file is available online. You can run it executing the command python exercise_19.py in a shell, and then following the instructions on screen to specify the intended input.