Python Dictionary Interview Questions (Top 50+)

Dictionaries are one of the most powerful data structures in Python. They store data in key-value pairs and are widely used in real-world applications.

In this tutorial, we cover the most frequently asked Python dictionary interview questions with examples and explanations.

1. Basic Dictionary Questions

Q1. What is a dictionary in Python?

A dictionary is a collection of key-value pairs.

Q2. How to create a dictionary?

              
Python

          Create dictionary
        
d = {"a": 1, "b": 2}

Q3. Are dictionary keys unique?

Yes, keys must be unique.

Q4. Can dictionary values be duplicated?

Yes, values can be duplicated.

2. Intermediate Questions

Q5. Access value using key

              
Python

          Access value
        
d = {"a": 10}
print(d["a"])

Q6. Add or update elements

              
Python

          Add/update
        
d = {}
d["x"] = 100
print(d)

Q7. Remove elements

              
Python

          Remove key
        
d.pop("a")

Q8. Iterate dictionary

              
Python

          Loop dictionary
        
for k, v in d.items():
    print(k, v)

3. Advanced Questions

Q9. Dictionary comprehension

              
Python

          Dict comprehension
        
squares = {x: x*x for x in range(5)}
print(squares)

Q10. Merge dictionaries

              
Python

          Merge dict
        
d1 = {"a":1}
d2 = {"b":2}
print({**d1, **d2})

Q11. Find key with max value

              
Python

          Max value key
        
d = {"a":10, "b":20}
print(max(d, key=d.get))

4. Coding Problems

Problem 1: Count frequency of elements

              
            
Python

          Frequency count
        
lst = [1,2,2,3]
freq = {}
for i in lst:
    freq[i] = freq.get(i, 0) + 1
print(freq)

Problem 2: Invert dictionary

              
Python

          Invert dict
        
d = {"a":1, "b":2}
inv = {v:k for k,v in d.items()}
print(inv)

Problem 3: Group anagrams

              
            
Python

          Group anagrams
        
words = ["eat","tea","tan","ate"]
d = {}
for w in words:
    key = ''.join(sorted(w))
    d.setdefault(key, []).append(w)
print(d.values())

5. Common Mistakes

1. Using mutable keys (not allowed).

2. Accessing non-existing keys without get().

3. Confusing keys and values.

4. Not understanding shallow copy.

6. Interview Tips

1. Use get() to avoid errors.

2. Practice dictionary problems.

3. Use defaultdict when needed.

4. Understand hashing concept.

7. Practice Questions

1. Merge multiple dictionaries.

2. Sort dictionary by value.

3. Find duplicate values.

4. Convert list to dictionary.

5. Count words in sentence.

Conclusion

Dictionaries are essential for efficient data handling in Python. Mastering dictionary operations will greatly improve your coding skills.

Practice regularly and explore real-world use cases to gain confidence in interviews.