Add ordered_dict.py

Author: yyossy5

src/basic/ordered_dict.py

@@ -0,0 +1,62 @@
+"""
+OrderedDict operations in Python.
+
+This module demonstrates the usage of collections.OrderedDict and its differences from regular dict:
+- OrderedDict maintains the order of item insertion
+- Key differences between OrderedDict and regular dict
+- Common OrderedDict operations and methods
+"""
+
+from collections import OrderedDict
+
+# When to use OrderedDict vs regular dict:
+# Use OrderedDict when:
+# - Order of insertion needs to be preserved and is meaningful
+# - You need equality comparisons that consider order
+# - You need to move items to the start/end of the dictionary
+
+# Use regular dict when:
+# - Order is not important
+# - Memory efficiency is a concern
+# - You're using Python 3.7+ and just need basic insertion order preservation
+#   (regular dict maintains insertion order since Python 3.7)
+
+# Key differences between dict and OrderedDict:
+# 1. Order matters in equality comparison
+dict1 = {"a": 1, "b": 2}
+dict2 = {"b": 2, "a": 1}
+print(dict1 == dict2)  # Output: True (order doesn't matter for regular dict)
+
+odict1 = OrderedDict([("a", 1), ("b", 2)])
+odict2 = OrderedDict([("b", 2), ("a", 1)])
+print(odict1 == odict2)  # Output: False (order matters for OrderedDict)
+
+# 2. Memory usage
+# OrderedDict uses more memory than regular dict as it maintains a doubly-linked list
+
+# Creating an OrderedDict
+# OrderedDict remembers the order in which keys were inserted
+ordered_fruits = OrderedDict()
+ordered_fruits["apple"] = 100
+ordered_fruits["banana"] = 200
+ordered_fruits["orange"] = 150
+# Output: OrderedDict([('apple', 100), ('banana', 200), ('orange', 150)])
+
+# Creating from list of tuples
+items = [("a", 1), ("b", 2), ("c", 3)]
+ordered_dict = OrderedDict(items)
+# Output: OrderedDict([('a', 1), ('b', 2), ('c', 3)])
+
+# Common operations (similar to regular dict)
+ordered_fruits["grape"] = 300  # Adding new element
+del ordered_fruits["apple"]  # Removing element
+price = ordered_fruits.pop("banana")  # Removing and returning value
+
+# OrderedDict specific operations
+# Moving element to end
+ordered_dict.move_to_end("a")
+# Output: OrderedDict([('b', 2), ('c', 3), ('a', 1)])
+
+# Moving element to beginning
+ordered_dict.move_to_end("a", last=False)
+# Output: OrderedDict([('a', 1), ('b', 2), ('c', 3)])