Dictionary keys, values, and items in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of dictionary keys() method

What is the output of this code snippet?

Python

my_dict = {'a': 1, 'b': 2, 'c': 3}
print(list(my_dict.keys()))

A ['a', 'b', 'c']

B ['1', '2', '3']

C ['a', 'b', 'c', 'd']

D dict_keys(['a', 'b', 'c'])

💡 Hint

The keys() method returns a view of the dictionary's keys. Converting it to a list shows the keys as a list.

The keys() method returns a view object showing the keys. Converting it to a list gives ['a', 'b', 'c']. Option A shows the view object itself, not a list.

❓ Predict Output

intermediate

Output of dictionary values() method

What will this code print?

Python

data = {'x': 10, 'y': 20}
vals = data.values()
print(sum(vals))

A 30

B ['10', '20']

C TypeError

D dict_values([10, 20])

💡 Hint

The values() method returns a view of values which can be summed directly.

The values() method returns a view of the dictionary's values. sum() can add these numbers directly, resulting in 30.

❓ Predict Output

advanced

Output of iterating dictionary items

What is the output of this code?

Python

d = {'one': 1, 'two': 2}
for k, v in d.items():
    print(f"{k}:{v}")

A 1\n2

B ('one', 1)\n('two', 2)

C one\ntwo

D one:1\ntwo:2

💡 Hint

items() returns key-value pairs which are unpacked in the loop.

The loop unpacks each key-value pair and prints them in the format key:value on separate lines.

❓ Predict Output

advanced

Length of dictionary keys view

What does this code print?

Python

my_dict = {1: 'a', 2: 'b', 3: 'c'}
keys_view = my_dict.keys()
print(len(keys_view))

A TypeError

B 3

C dict_keys([1, 2, 3])

D 0

💡 Hint

The keys view supports len() to get the number of keys.

The keys() method returns a view of keys which supports len(), returning the number of keys in the dictionary.

❓ Predict Output

expert

Output of modifying dictionary during iteration

What happens when this code runs?

Python

d = {'a': 1, 'b': 2, 'c': 3}
for k in d.keys():
    if k == 'b':
        d.pop(k)
print(d)

A {'a': 1, 'c': 3}

B {'a': 1, 'b': 2, 'c': 3}

C RuntimeError: dictionary changed size during iteration

D {'a': 1, 'b': 2}

💡 Hint

Modifying a dictionary while iterating over its keys causes an error.

Python raises a RuntimeError if the dictionary size changes during iteration over keys or items.