Tech With Galvan

Tuples and Sets — When and Why

Lists are the general-purpose container. But two specialized cousins solve specific problems better: tuples (unchangeable sequences) and sets (uniqueness machines).

Tuples: lists that took a vow

A tuple is a list that can never change — same syntax, round brackets:

code

coordinates = (28.6139, 77.2090)     # Delhi's location
rgb = (255, 128, 0)
date_of_birth = ("2009", "August", "15")

Everything you know about lists works: indexing, slicing, len(), in, loops:

code

print(coordinates[0])      # 28.6139
print(rgb[-1])             # 0
lat, lng = coordinates     # UNPACKING — a tuple superpower!
print(lat, lng)            # 28.6139 77.2090

That unpacking move is everywhere — you already used it: left, right = st.columns(2) returns a tuple, and you unpacked it.

Why tuples exist (the point of "unchangeable")

code

coordinates[0] = 40      # TypeError: 'tuple' object does not support item assignment

That restriction is a feature. Use a tuple when the data is a fixed unit:

Coordinates that must stay paired

Days of the week

A function returning multiple values (return lat, lng — that's a tuple!)

If code tries to modify it, Python crashes loudly — protecting data that shouldn't change. Lists say "edit me"; tuples say "I am what I am."

Sets: automatic uniqueness

A set is an unordered collection where every value appears at most once:

code

visited = {"Delhi", "Mumbai", "Delhi", "Goa", "Mumbai"}
print(visited)              # {'Delhi', 'Mumbai', 'Goa'} — duplicates vanished!

Curly brackets, no keys (that's a dict you'll meet next lesson), duplicates silently dropped.

The killer use case: deduplication

code

votes = ["Aarav", "Diya", "Aarav", "Kabir", "Diya", "Aarav"]

unique_voters = set(votes)
print(len(votes), "votes,", len(unique_voters), "unique voters")
# 6 votes, 3 unique voters

print(list(unique_voters))   # back to a list if you need one

One conversion, every duplicate gone. Doing this manually with loops takes ten lines.

Set operations — the math you'll actually use

code

python_devs = {"Aarav", "Diya", "Kabir"}
js_devs = {"Diya", "Rohan"}

print(python_devs | js_devs)    # union: everyone           {'Aarav','Diya','Kabir','Rohan'}
print(python_devs & js_devs)    # intersection: in BOTH     {'Diya'}
print(python_devs - js_devs)    # difference: only python   {'Aarav', 'Kabir'}

print("Diya" in python_devs)    # True — membership (very fast!)

Union, overlap, and "who's only in this group" — real questions, one symbol each.

The fast membership secret

code

big_list = list(range(1_000_000))
big_set = set(big_list)

# 999999 in big_list   → scans one by one... slow
# 999999 in big_set    → jumps almost instantly... fast

Sets check membership dramatically faster than lists. When you need "have I seen this before?" on lots of data — set, not list.

Common Errors & Fixes

`TypeError: 'tuple' object does not support item assignment` — you tried to change a tuple. Convert if you must: my_list = list(my_tuple).

`{}` is an empty DICT, not a set — the empty set is set(). Classic trap.

Sets have no order — don't index them (s[0] fails); convert to a list if order matters.

✅ Checkpoint

What's the key difference between a list and a tuple? *(Mutability — tuples never change)*

set([1, 1, 2, 3, 3]) gives? *({1, 2, 3})*

How do you get items in BOTH sets A and B? *(A & B)*

lat, lng = (28.6, 77.2) — what's this called? *(Unpacking)*

Next: dictionaries — the container that runs the internet.