🎯 What you will learn
- Write list comprehensions
- Sort and filter data
- Calculate averages, max and min
👋 Let’s get started!
Data scientists turn piles of numbers into answers 📊. Who scored highest? What’s the average? Python makes it fast — often in just one line.
🪜 Step by step
1. ⚡ List comprehensions
Build a new list in one line: [expression for item in list if condition]
nums = [1, 2, 3, 4, 5, 6]
evens = [n for n in nums if n % 2 == 0]
squares = [n * n for n in nums]
print(evens, squares)2. 🔃 Sorting
sorted() returns a sorted copy. key= chooses what to sort by.
players = [("Ana", 88), ("Ben", 95), ("Cho", 72)]
ranked = sorted(players, key=lambda p: p[1], reverse=True)
print(ranked[0])3. 🧮 Summaries
sum(), max(), min() and len() answer big questions.
temps = [70, 75, 68, 80, 77]
print("Average:", sum(temps) / len(temps))
print("Hottest:", max(temps))🧪 Try it!
Change the code and press ▶ Run to see what happens. You can’t break anything!
Class survey analyzer
answers = ["pizza", "tacos", "pizza", "sushi", "pizza", "tacos"]
counts = {}
for food in answers:
counts[food] = counts.get(food, 0) + 1
for food, n in sorted(counts.items(), key=lambda x: x[1], reverse=True):
print(f"{food:<6} {'█' * n} {n}")Top score
scores = [42, 97, 65]
best = max(scores)
print("Best:", best)📖 Key words
Tap a card to flip it over!
- List comprehension
- A one-line list builder ⚡
- sorted()
- Returns a sorted copy 🔃
- lambda
- A tiny unnamed function λ
- Average
- Sum divided by count ➗
🏆 Challenge
Print a list of the names of everyone who scored 80 or more, in the original order.
Challenge
results = [("Ana", 88), ("Ben", 95), ("Cho", 72)]
Knowledge Check Quiz
- What prints?
- What does sorted(x, reverse=True) do?
- What prints?