Python · Theory

dict.setdefault()

Theory

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dict.setdefault() works on a dictionary — labelled data like marks["Asha"] = 90. Keys map to values. Loop with .items() when you need both.

dict.setdefault() — output — 90, then 0, then {'Asha': 90, 'Neha': 0}. setdefault adds only if missing.

Trap for dict.setdefault() — writing d[missing] in a viva. Prefer get when the key might not exist.

Diagram

{ "Asha": 90, "Ravi": 85 }
         │           │
        key        value

Exam tip

get vs [] — one sentence + tiny dict of marks.

# dict.setdefault()
d = {"Asha": 90}
print(d.setdefault("Asha", 0))
print(d.setdefault("Neha", 0))
print(d)

dict.setdefault() — output: 90, then 0, then {'Asha': 90, 'Neha': 0}. setdefault adds only if missing.