Collections Module Overview

The collections module provides specialized container alternatives to Python's built-in containers like list, dict, set, and tuple. Key components include:

• namedtuple: Creates tuple subclasses with named fields
• deque: Double-ended queue for efficient appends/pops
• Counter: Dictionary subclass for counting hashable objects
• OrderedDict: Dictionary that preserves insertion order

Named Tuple Implementation

namedtuple combines tuple benefits with attribute-style access:

Tuple Fundamentals

# Tuple unpacking examples
coordinates = ('x_val', 'y_val')
point = (*coordinates, 'z_val', 'w_val')

x, y = coordinates
first, *remaining = point

print(x, y)
print(first, remaining)

Named Tuple Creation

from collections import namedtuple

Person = namedtuple('Person', ['first_name', 'last_name', 'age'])

# Create instance
p = Person(first_name='Jane', last_name='Doe', age=30)
print(p._fields)  # Output: ('first_name', 'last_name', 'age')

# Access attributes
print(p.first_name)  # Output: Jane

Advanced Usage

from collections import namedtuple

Employee = namedtuple('Employee', ['id', 'department', 'level'])

# Create from iterable
emp_data = ['E123', 'Engineering', 'L4']
e1 = Employee._make(emp_data)

# Create from dictionary
emp_dict = {'id': 'E456', 'department': 'Marketing', 'level': 'L3'}
e2 = Employee(**emp_dict)

# Field modification
e1 = e1._replace(level='L5')
print(e1._asdict())  # Convert to OrderedDict

Other Collection Types

Counter Implementation

from collections import Counter

class CounterOperations:
    def run_examples(self):
        c1 = Counter()
        words = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
        for word in words:
            c1[word] += 1
        
        c2 = Counter({'cats': 5, 'dogs': 3})
        c3 = Counter(a=3, b=2, c=1, d=0)
        
        print(c1.most_common(2))  # Top 2 frequent items
        print(list(c3.elements()))  # Non-zero elements
        
        c3.subtract(c1)
        print(c3)
        
        c3.update(c2)
        print(c3 + c2)

if __name__ == "__main__":
    ops = CounterOperations()
    ops.run_examples()

Deque Characteristics

Double-ended queues provide efficient O(1) operations for appending and popping from either end, ideal for queue implementations and sliding window algorithms.

Defaultdict Behavior

Automatically initailizes missing keys with default values, reducing key existence checks in dictionary operations.