intermediateLibraries

Collections Module

Specialized container types: Counter, defaultdict, namedtuple, deque.

In this lesson

01Counter & defaultdict
02namedtuple & deque

01Counter & defaultdict

Powerful alternatives to plain dictionaries.

Python

1from collections import Counter, defaultdict
2
3# Counter - count occurrences
4words = "the cat sat on the mat the cat".split()
5counts = Counter(words)
6print(counts.most_common(3))
7
8# defaultdict - auto-create missing keys
9groups = defaultdict(list)
10for name, score in [("Alice", 90), ("Bob", 85), ("Alice", 95)]:
11    groups[name].append(score)
12print(dict(groups))

Output

[('the', 3), ('cat', 2), ('sat', 1)]
{'Alice': [90, 95], 'Bob': [85]}

02namedtuple & deque

Lightweight data structures for specific use cases.

Python

1from collections import namedtuple, deque
2
3# namedtuple - readable tuple alternative
4Point = namedtuple("Point", ["x", "y"])
5p = Point(3, 4)
6print(f"x={p.x}, y={p.y}")
7
8# deque - fast appends/pops from both ends
9d = deque([1, 2, 3])
10d.appendleft(0)
11d.append(4)
12d.rotate(1)
13print(list(d))

Output

x=3, y=4
[4, 0, 1, 2, 3]

Data Classes