PCEP Certification Practice: Checking the Existence of Dictionary Keys

Question 1: What is the most common way to check if a key exists in a dictionary?

1. my_dict.has_key('key')
2. 'key' in my_dict
3. my_dict['key']
4. my_dict.key_exists('key')

Question 2: Which of the following methods can be used to check if a key exists in a dictionary? (Choose all that apply)

1. if 'key' in my_dict:
2. if my_dict.get('key') is not None:
3. if my_dict.has_key('key'):
4. if 'key' not in my_dict:

Question 3: Complete the code to print "Key exists" if the key 'age' exists in the dictionary person.

person = {'name': 'Alice', 'age': 30}
if ______:
    print("Key exists")

Question 4: What will be the output of the following code?

my_dict = {'a': 1, 'b': 2, 'c': 3}
if 'b' in my_dict:
    print("Found")
else:
    print("Not Found")

1. Found
2. Not Found
3. Error
4. None

Question 5: Insert the correct code to print "Key not found" if the key 'city' is not present in the dictionary person.

person = {'name': 'Alice', 'age': 30}
if ______:
    print("Key not found")

Question 6: What is the result of the following code?

person = {'name': 'Bob', 'age': 25}
if 'address' in person:
    print("Address found")
else:
    print("Address not found")

1. Address found
2. Address not found
3. Error
4. None

Question 7: Which of the following statements correctly check for the existence of a key in a dictionary? (Choose all that apply)

1. if 'key' in my_dict:
2. if my_dict.get('key') is None:
3. if my_dict.get('key', 'default') == 'default':
4. if my_dict['key'] == None:

Question 8: Arrange the steps to correctly check if a key exists in a dictionary and print a message accordingly.

1. Use an if statement to check if the key exists.
2. Print "Key exists" if the key is found.
3. Define the dictionary person.

Question 9: Complete the code to print "Key found" if the key 'email' exists in the dictionary contact.

contact = {'name': 'John', 'phone': '123-456-7890'}
if ______:
    print("Key found")

Question 10: What will be the output of the following code?

inventory = {'apples': 10, 'bananas': 5}
if 'oranges' not in inventory:
    print("Out of stock")

1. Out of stock
2. In stock
3. Error
4. None

Question 11: Insert the correct code to check if the key 'username' does not exist in the dictionary user_data and add it if it doesn't.

user_data = {'email': '[email protected]'}
if ______:
    user_data['username'] = 'new_user'

Question 12: What will happen if you try to check the existence of a key using the expression if my_dict['key'] when the key does not exist?

1. A new key-value pair is added to the dictionary.
2. The program raises a KeyError.
3. The program returns None.
4. The program prints False.

Question 13: Which of the following are safe ways to check if a key exists in a dictionary without raising an error? (Choose all that apply)

1. 'key' in my_dict
2. my_dict.get('key')
3. my_dict['key']
4. 'key' not in my_dict

Question 14: Arrange the steps to correctly check if a key exists and return a default value if it does not.

1. Use the get() method with a default value.
2. Define the dictionary config.
3. Print the retrieved value or the default value

Question 15: Complete the code to safely retrieve the value of the key 'password' from the dictionary login_info or return 'Not set' if the key does not exist.

login_info = {'username': 'admin'}
password = login_info.get('password', ______)
print(password)

Question 16: What will be the output of the following code?

settings = {'theme': 'dark', 'notifications': True}
if 'volume' not in settings:
    print("Default volume setting")

1. None
2. Default volume setting
3. Error
4. True

17. Insert the correct method to retrieve the value of the key 'api_key' from the dictionary config, or return 'No API key' if the key does not exist.

config = {'version': '1.0'}
api_key = config.______ ('api_key', 'No API key')
print(api_key)

Question 18: Which statement is true about checking the existence of keys in a Python dictionary?

1. Using my_dict['key'] will return None if the key doesn't exist.
2. Using 'key' in my_dict will raise a KeyError if the key doesn't exist.
3. Using my_dict.get('key') is a safe way to check for the existence of a key.
4. Using my_dict.keys() is required to check if a key exists.

Question 19: Which of the following methods allow you to check for the existence of a key and retrieve its value if it exists? (Choose all that apply)

1. my_dict['key']
2. my_dict.get('key')
3. 'key' in my_dict
4. my_dict.setdefault('key', 'default')

Question 20: Arrange the steps to correctly check if a key exists in a dictionary and add a new key-value pair if it doesn't.

1. Use the not in operator to check if the key exists.
2. Add the new key-value pair.
3. Define the dictionary preferences.

Question 21: Complete the code to add the key 'location' with the value 'unknown' to the dictionary data only if the key doesn't already exist.

data = {'name': 'Alice'}
if 'location' ______ data:
    data['location'] = 'unknown'

Question 22: What will be the output of the following code?

preferences = {'theme': 'light', 'language': 'English'}
if 'font_size' not in preferences:
    preferences['font_size'] = '12pt'
print(preferences)

1. {'theme': 'light', 'language': 'English'}
2. {'theme': 'light', 'language': 'English', 'font_size': '12pt'}
3. {'font_size': '12pt'}
4. Error

Question 23: Insert the correct code to check if the key 'admin' exists in the dictionary users and print a message if it does.

users = {'user1': 'Alice', 'user2': 'Bob', 'admin': 'Charlie'}
if ______:
    print("Admin exists")

Question 24: What will happen if you use the get() method to check for a key that does not exist and provide a default value?

1. The method returns the default value.
2. The method raises a KeyError.
3. The method returns None.
4. The method adds the key to the dictionary with the default value.

Question 25: Which of the following statements correctly check for the existence of a key in a dictionary and handle it safely? (Choose all that apply)

1. if 'key' in my_dict:
2. value = my_dict.get('key', 'default_value')
3. if 'key' not in my_dict:
4. value = my_dict['key']