Custom Class Iteration¶

You can create iterable custom classes by implementing __getitem__ and __len__.

Required Methods¶

Method	Signature	Purpose
`__getitem__`	`(self, index: int) -> T`	Get element at index
`__len__`	`(self) -> int`	Return number of elements

Example¶

class MyList:
    pub data: list[int]

    pub def __new__(self, values: list[int]):
        self.data = values

    pub def __getitem__(self, index: int) -> int:
        return self.data[index]

    pub def __len__(self) -> int:
        return len(self.data)

def main() -> int:
    let arr = MyList([10, 20, 30, 40, 50])

    for x in arr:
        print(x)  # Prints: 10 20 30 40 50

    return 0

How It Works¶

When you write for x in custom_obj:, the compiler:

Calls obj.__len__() to get the count
Loops from 0 to count-1
Calls obj.__getitem__(index) for each element

Negative Indexing¶

Since __getitem__ is called directly, negative indexing works if your implementation supports it:

pub def __getitem__(self, index: int) -> int:
    return self.data[index]  # data[-1] will work!