DSA: The 8-Week Grind — Day 6

Other Python Data Structure Methods — Tuples, Sets, Dictionaries & Deques

“Strings and lists are half the game. Today, we unlock the rest.”

---

🟡 Why This Day Matters

You’ve mastered strings and lists — now it’s time to learn the other core Python data structures that keep showing up in DSA problems.
Today’s focus:

• Tuples (immutable sequences)

• Sets (unique items)

• Dictionaries (key-value mapping)

• Deque (double-ended queue)

---

🔹 TUPLES — Immutable Sequences

Description: Tuples work like lists, but they cannot be modified after creation. Perfect for fixed collections or as keys in dictionaries.

---

✅ Create and Access

pythonCopyt = (1, 2, 3)
print(t[0])   # Output: 1
print(len(t)) # Output: 3

---

✅ count() — Count occurrences

Description: Returns how many times a value appears in the tuple.

pythonCopyt = (1, 2, 2, 3)
print(t.count(2))  # Output: 2

---

✅ index() — Find the position of a value

Description: Returns the index of the first occurrence of a value.

pythonCopyprint(t.index(3))  # Output: 3

---

🔹 SETS — Unique, Unordered Collections

Description: Sets store unique elements in no particular order and are very fast for membership checks.

---

✅ Create and Check Membership

pythonCopys = {1, 2, 3}
print(2 in s)  # Output: True

---

✅ add() — Add a single element

Description: Inserts a new element into the set.

pythonCopys.add(4)
print(s)  # Output: {1, 2, 3, 4}

---

✅ update() — Add multiple elements

Description: Inserts multiple values from an iterable into the set.

pythonCopys.update([5, 6])
print(s)  # Output: {1, 2, 3, 4, 5, 6}

---

✅ remove() vs discard() — Remove elements

Description: remove() raises an error if element not found, discard() doesn’t.

pythonCopys.remove(4)
s.discard(10)  # No error
print(s)       # Output: {1, 2, 3, 5, 6}

---

✅ Set Operations — union(), intersection(), difference()

Description: Combine sets, find common elements, or find unique elements.

pythonCopya = {1, 2, 3}
b = {3, 4, 5}
print(a.union(b))         # Output: {1, 2, 3, 4, 5}
print(a.intersection(b))  # Output: {3}
print(a.difference(b))    # Output: {1, 2}

---

🔹 DICTIONARIES — Key-Value Storage

Description: Stores data in {key: value} format for quick lookups.

---

✅ Create and Access

pythonCopyd = {"name": "Goutham", "age": 24}
print(d["name"])      # Output: Goutham
print(d.get("city"))  # Output: None

---

✅ keys(), values(), items() — View contents

Description: Retrieve all keys, values, or both.

pythonCopyprint(list(d.keys()))   # Output: ['name', 'age']
print(list(d.values())) # Output: ['Goutham', 24]
print(list(d.items()))  # Output: [('name', 'Goutham'), ('age', 24)]

---

✅ update() — Merge dictionaries

Description: Adds or updates key-value pairs from another dictionary.

pythonCopyd.update({"city": "Hyderabad"})
print(d)  # Output: {'name': 'Goutham', 'age': 24, 'city': 'Hyderabad'}

---

✅ pop() — Remove a key by name

Description: Deletes the specified key and returns its value.

pythonCopyd.pop("age")
print(d)  # Output: {'name': 'Goutham', 'city': 'Hyderabad'}

---

✅ popitem() — Remove last inserted pair

Description: Removes and returns the last key-value pair.

pythonCopyd.popitem()
print(d)  # Output: {'name': 'Goutham'}

---

🔹 DEQUE — Double-Ended Queue

Description: From collections, lets you add/remove from both ends in O(1) time.

---

✅ Create a Deque

pythonCopyfrom collections import deque
dq = deque([1, 2, 3])
print(dq)  # Output: deque([1, 2, 3])

---

✅ append() and appendleft() — Add to ends

Description: Add elements to right or left end.

pythonCopydq.append(4)
dq.appendleft(0)
print(dq)  # Output: deque([0, 1, 2, 3, 4])

---

✅ pop() and popleft() — Remove from ends

Description: Remove and return elements from right or left end.

pythonCopydq.pop()
dq.popleft()
print(dq)  # Output: deque([1, 2, 3])

---

✅ extend() and extendleft() — Add multiple elements

Description: Add elements from iterable to right or left end.

pythonCopydq.extend([5, 6])
dq.extendleft([-1, -2])
print(dq)  # Output: deque([-2, -1, 1, 2, 3, 5, 6])

---

🟢 Day 6 Takeaways

✅ Tuples: Immutable, safe for fixed data
✅ Sets: Unique, fast membership checks
✅ Dictionaries: Key-value data mapping
✅ Deque: Efficient double-ended operations

---