Python Structs, Associated Functions & Methods (impl)
Structs allow you to name and package multiple related values into a cohesive custom type. Methods are defined inside impl blocks and take &self as their first parameter, while associated functions (like Self::new) act as constructors without &self.
"A struct is like an architect’s blueprint for a house specifying dimensions and materials. An impl block is the user manual explaining what that house can do (like house.turn_on_lights())."
Deep Dive: How It Works
Struct Definition: struct User { username: String, active: bool }
Methods with &self: Borrow the struct instance immutably to read its fields.
Associated Functions (Self::new): Functions associated with the type but not an instance (called with Type::function()).
Syntax Blueprint
impl Rectangle { fn area(&self) -> u32 { self.width * self.height } }Define methods inside impl blocks with &self to access fields.
Core Rules to Remember
Common Beginner Traps & How to Fix Them
Forgetting &self in method signatures.Why it happens: Writing fn area(self) consumes ownership of the instance, preventing you from using it again.
How to fix: Use &self for read-only methods and &mut self for mutating methods.
Live Interactive Example
Hit Run Code to see it liveYour Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Implement a BankAccount struct
- Create struct BankAccount { balance: i32 }
- Implement impl BankAccount with fn new(balance: i32) -> Self { Self { balance } } and fn get_balance(&self) -> i32 { self.balance }
- In main(), let acc = BankAccount::new(500); print "Account Balance: $500".
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