Python practice

Python dictionary practice questions

16 problems, ordered from easiest. They run in your browser, and 7 are free.

The idea in a minute

A dictionary stores values under keys, so you can look something up by name instead of by position. It is the tool for counting, grouping and quick lookups.

Most problems here follow one pattern: walk through the data once, and update a dictionary as you go.

Example: Group names by city

people = [("Asha", "Pune"), ("Ravi", "Delhi"), ("Meera", "Pune")]
by_city = {}
for name, city in people:
    by_city.setdefault(city, []).append(name)
print(by_city)

What it prints

{'Pune': ['Asha', 'Meera'], 'Delhi': ['Ravi']}

What to watch for

Use get(key, default) so a missing key does not raise an error.
Keys must be unchangeable, so a list cannot be a key but a tuple can.
Looping over a dictionary gives its keys. Use .items() for keys and values.

Dictionaries problems

Want a guided order across every topic? Open the practice sheets or the Python hub.