Python Programs on Dictionaries

1. Write a python program for demonstrating the
• creation of dictionary
• accessing dictionary elements
• modifying dictionary elements
• finding length and possible operations.
2. Write a python program to create a dictionary of students with keys as roll numbers and values as names. Perform operations like insert, update and modify student data.

Logic:

• Initialize a dictionary using curly braces {} with key-value pairs. Keys can be strings, numbers, or tuples, values can be any type (strings, lists, dictionaries, etc.).
  sample_dict = {"name": "ipl", "age": 18, "city": "Mumbai", "hobbies": ["cricket", "football"]}
• Updating existing keys with new values (dict[key] = value).
• Use del to remove a specific key or pop(key, default) to remove and return a value.

Program:

Copy

# a) Program to demonstrate dictionary operations

# 1. Creating a dictionary
sample_dict = {"name": "Ram", "age": 25, "city": "New York", "hobbies": ["reading", "cycling"] }
print("Original dictionary:", sample_dict)

# 2. Accessing dictionary elements
print("\n Accessing elements:")
print("Name:", sample_dict["name"])
print("Hobbies:", sample_dict.get("hobbies"))

# 3. Modifying dictionary elements
print("\nModifying elements:")
sample_dict["age"] = 26  # Update existing key
sample_dict["city"] = "Boston"  # Update existing key
print("After modifying age and city:", sample_dict)

# 4. Adding new key-value pairs
sample_dict["occupation"] = "Scientist"  # Add new key-value pair
print("After adding occupation:", sample_dict)

# 5. Finding the length of the dictionary
print("\n Length of dictionary:", len(sample_dict))

# 6. Other possible operations
print("\n Other operations:")
# Removing a key-value pair
del sample_dict["hobbies"]
print("After removing hobbies:", sample_dict)

# Using pop() to remove and return a value
city = sample_dict.pop("city")
print("Popped city:", city)
print("After popping city:", sample_dict)


# Iterating over keys
print("Keys:")
for key in sample_dict:
    print(key)

# Iterating over values
print("Values:")
for value in sample_dict.values():
    print(value)

# Iterating over key-value pairs
print("Key-Value pairs:")
for key, value in sample_dict.items():
    print(f"{key}: {value}")

# Clearing all items
sample_dict.clear()
print("After clearing dictionary:", sample_dict)

Output:

Copy

####### b) Student Dictionary with Interactive Operations  ########

# Initialize student dictionary
students = {101: "kgps", 102: "kbk", 103: "grs"}
print("Initial student dictionary: {}".format(students))

while True:
    print("\n Options: 1=Insert, 2=Update, 3=Delete, 4=Display, 5=Exit")
    
    choice = input("Enter your choice (1-5): ").strip()

    if choice == "1":  # Insert new student
        roll_no_input = input("Enter roll number: ").strip()
        roll_no = int(roll_no_input)
        if roll_no in students:
            print("Roll number %d already exists!" % roll_no)
        else:
            name = input("Enter student name: ").strip()
            students[roll_no] = name
            print("Student added: {}: {}".format(roll_no, name))
            
    elif choice == "2":  # Update existing student
        roll_no_input = input("Enter roll number to update: ").strip()
        roll_no = int(roll_no_input)
        if roll_no in students:
            name = input("Enter new name: ").strip()
            students[roll_no] = name
            print("Updated student: {}: {}".format(roll_no, name))
        else:
            print("Roll number %d not found!" % roll_no)

    elif choice == "3":  # Delete student
        roll_no_input = input("Enter roll number to delete: ").strip()
        roll_no = int(roll_no_input)
        if roll_no in students:
            name = students.pop(roll_no)
            print("Deleted student: {}: {}".format(roll_no, name))
        else:
            print("Roll number %d not found!" % roll_no)

    elif choice == "4":  # Display all students
        if students:
            print("Student list:")
            for roll_no, name in students.items():
                print("Roll: %d, Name: %s" % (roll_no, name))
        else:
            print("No students in dictionary!")

    elif choice == "5":  # Exit
        print("Exiting program...")
        break

    else:
        print("Invalid choice! Please enter 1-5.")

Output: