Counter
- Python course
- Intermediate
- Lesson 88/116
- 5 min
Learn counting with Counter.
Counter
Counter is a dictionary type from the collections module that counts how many of each item there is. It quickly gives the count of items in a list, string or any iterable.
Example: Counter("apple") produces {'p': 2, 'a': 1, 'l': 1, 'e': 1}. Writing c["p"] returns 2. With c.most_common(2) you can get the two most frequent items. Counter is very useful for word frequency or vote counting.
The most_common method
most_common(n) returns the n most frequent items as a list of (item, count) tuples. Counts are in decreasing order; the most frequent item is first.
Example: Counter([1, 1, 2, 3, 1]).most_common(2) returns [(1, 3), (2, 1)]. So 1 appeared three times, 2 once. If n is not given, all items are returned as a sorted list. This method is ideal for finding the most frequent values quickly.
Practice Count letters with Counter
Start with from collections import Counter. Create a Counter with c = Counter("apple") and print the count of p with print(c["p"]).
Starter code
# Count letters with CounterSample solution
# Count letters with Counter
from collections import Counter
c = Counter("apple")
print(c["p"])Expected output
2
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which module does Counter come from?
- functools
- collections Correct answer
- itertools
- typing
Explanation: Counter is in the collections module.
2 Counter import line
from collections import ____
c = Counter("apple")
print(c["p"])from collections import Counter
c = Counter("apple")
print(c["p"])Explanation: Counter is imported from the collections module.
3 Match the Counter parts
| Term | Meaning |
|---|---|
Counter |
Counting dict |
c["p"] |
Item count |
most_common |
Most frequent |
collections |
Module |