PPA-5

Question

Write the following functions:

  • dict_to_list: accept a dictionary D as argument. Return the key-value pairs in D as a list L of tuples. That is, every element of L should be of the form (key, value) such that D[key] = value. Going the other way, every key-value pair in the dictionary should be present as a tuple in the list L.
  • list_to_dict: accept a list of tuples L as argument. Each element of L is of the form (x, y). Return a dict D such that each tuple (x, y) corresponds to a key-value pair in D. That is, D[x] = y.
  • For the function dict_to_list, the order in which the key-value pairs are appended to the list doesn’t matter.
  • For the function list_to_dict, you can assume that if (x1, y1) and (x2, y2) are two different elements in L, x1 != x2. Why is this assumption important?
  • You do not have to accept input from the user or print the output to the console. You just have to write the definition of both the functions.

Hint

  • For the function dict_to_list, execute list(D.items()) and observe what you get.
  • For the function list_to_dict, execute dict(L) and observe what you get.

Solutions

Refer to this document and this document for more details regarding some aspects of dictionaries.

def dict_to_list(D):
    L = [ ]
    for key, value in D.items():
        L.append((key, value))
    return L

def list_to_dict(L):
    D = dict()
    for key, value in L:
        D[key] = value
    return D
def dict_to_list(D):
    return list(D.items())

def list_to_dict(L):
    return dict(L)

Video Solution