Named Tuples and OrderedDict

Introduction

OrderedDict maintains insertion order, useful when order matters and you need dict features.

OrderedDict Basics

from collections import OrderedDict

od = OrderedDict()
od["a"] = 1
od["b"] = 2
od["c"] = 3

# Preserves insertion order
for k, v in od.items():
    print(k, v)

Move to End/Start

od = OrderedDict({"a": 1, "b": 2, "c": 3})

od.move_to_end("a")     # Move 'a' to end
od.move_to_end("a", last=False)  # Move to start

# Reverse iteration
for k in reversed(od):
    print(k)

Comparison

from collections import OrderedDict

od1 = OrderedDict({"a": 1, "b": 2})
od2 = OrderedDict({"b": 2, "a": 1})
d = {"a": 1, "b": 2}

# OrderedDict considers order
print(od1 == od2)  # False
print(dict(od1) == d)  # True (regular dict, Python 3.7+)

Practice Problems

1. Create LRU cache with OrderedDict
2. Track access order of items
3. Implement most recently used tracking
4. Reorder dictionary by values
5. Serialize OrderedDict to JSON