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STUDENT NOTES · DAY 7 OF 24
A Train of Boxes 📦📦📦
One box holds one thing. A LIST is a whole train of boxes under one name — and every wagon has a number.
1Meet the list
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Py: 60 students = 60 variables? No way. ONE list holds them all. The wagons are numbered starting from 0 — that surprises everyone once!
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Professor Hoot: marks[0] is the FIRST wagon. And marks[-1] counts from the back — the last one. Very handy.
2Lists grow and shrink
List builder — add your own wagons!
snacks = []
3Loop + list = power couple
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Bittu: sum, max, min, len — I compute these for a million students before you blink.
4Changing a wagon — and Bugly's trap
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Bugly: Hehehe… there are only wagons 0, 1, 2. Ask for wagon 3 and—
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Py: IndexError = you asked for a wagon that doesn't exist. Check len() when unsure.
5Quick quiz! 🧠
fruits = ["mango", "apple", "banana"]. What is fruits[1]?
💡 Counting starts at 0: mango is [0], apple is [1].
What does fruits[-1] give?
💡 -1 counts from the back: the LAST item. banana wins.
6Your mission 🚀
Mission 1: Make a list of your 4 favourite foods. Print the first and the last using [0] and [-1].
Mission 2: Append a 5th food, then print the new len().
Mission 3: Make a marks list and print the average: sum(marks) / len(marks).
Day 7 done — the train is yours! 🚂
Next: strings — slicing words, shouting in CAPITALS, and secret reversing.
Go to Day 8: Strings →