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STUDENT NOTES · DAY 11 OF 24
The Magic Register 📖
A list numbers its wagons. A dictionary NAMES them — like the class register: name on the left, marks on the right.
1Keys and values
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Py: A dictionary stores pairs: key → value. Ask by NAME, get the answer instantly — no counting wagons.
2Add, update, remove
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Bittu: Assigning to a NEW key adds it. Assigning to an OLD key replaces it. I never keep two entries with the same key.
3Bugly's trap: the missing key
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Bugly: Ask for someone who is not in the register… hehehe:
The polite fix — .get() with a backup answer:
Register lookup — try a name!
Renu → 78
register = {"Renu": 78, "Akash": 92, "Priya": 65}
4Looping through the register
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Professor Hoot: .items() hands you both halves of each pair. The most useful dict loop there is.
5Quick quiz! 🧠
d = {"a": 1}. What does d["z"] do?
💡 Square brackets on a missing key crash with KeyError. Use d.get("z", "backup") to stay safe.
Which loop gives you keys AND values?
💡 .items() yields (key, value) pairs — unpack them into two names.
6Your mission 🚀
Mission 1: Make a menu dict: {"samosa": 15, "chai": 10, "momo": 40}. Print the price of momos.
Mission 2: Add "dosa": 50, then print the whole menu with a .items() loop like "samosa costs ₹15".
Mission 3: Use .get() to ask for "pizza" with the backup answer "not on the menu!".
Day 11 done — registrar of power! 📖
Next: tuples that never change and sets that hate duplicates.
Go to Day 12: Tuples & Sets →