Question

Write a Python program that allows the user to perform three operations (implemented as three functions) on a dictionary:

add_to_dict(): takes a dictionary, a key, a value and adds the <key,value> pair to the dictionary. If the key is already in the dictionary, then the program displays the error message: "Error. Key already exists.".
remove_from_dict(): takes a dictionary and key and removes the key from the dictionary. If no such key is found in the dictionary then the program prints: "Key not found."
find_key(): takes dictionary and key and returns the value associated with the key or None if not found. The program prints the value if found, else prints: "Key not found."
No printing should be done inside these three functions.

The user is presented with a menu and repeatedly offered to perform an operation until he/she quits.

Finally, a list of the key-value pairs in the dictionary is printed out.

The main program is given - do not change it.

Example 1:

Menu: 
(a)dd, (r)emove, (f)ind: a
Key: rich
Value: 1
More (y/n)? y
Menu: 
(a)dd, (r)emove, (f)ind: a
Key: alireza
Value: 2
More (y/n)? n
[('alireza', '2'), ('rich', '1')]

def main():
    more_input = True
    a_dict = {}
  
    while more_input:    
        choice = menu_selection()
        execute_selection(choice, a_dict)
        again = input("More (y/n)? ")
        more_input = again.lower() == 'y'
  
    tuple_list = dict_to_tuples(a_dict)
    print(sorted(tuple_list))

main()

Answer 1

def add_to_dict(d, key, value):
    if key not in d:
        d[key] = value
        return 1
    else:
        return 0


def remove_from_dict(d, key):
    if key in d:
        del d[key]
        return 1
    else:
        return 0

def find_key(d, key):
    if key in d:
        return d[key]
    else:
        return None

def execute_selection(choice, a_dict):
    if(choice.lower()=="a"):
        key = input("Key: ")
        value = input("Value: ")
        result = add_to_dict(a_dict,key, value)
        if result==0:
            print("Error. Key already exists.")
    elif(choice.lower()=="r"):
        key = input("Key: ")
        result = remove_from_dict(a_dict, key)
        if result==0:
            print("Key not found.")
    elif(choice.lower()=="f"):
        key = input("Key: ")
        result = find_key(a_dict, key)
        if result==None:
            print("Key not found.")
        else:
            print(result)


def menu_selection():
    choice = input("Menu: (a)dd, (r)emove, (f)ind: ")
    return choice
def dict_to_tuples(d):
    list = [(k, v) for k, v in d.items()]
    return list
def main():
    more_input = True
    a_dict = {}
  
    while more_input:    
        choice = menu_selection()
        execute_selection(choice, a_dict)
        again = input("More (y/n)? ")
        more_input = again.lower() == 'y'
  
    tuple_list = dict_to_tuples(a_dict)
    print(sorted(tuple_list))

main()

NOTE: The above code is in Python3. Please refer to the attached screenshots for code indentation and sample I/O.

SAMPLE I/O: