Iteration in Sifr

Sifr keeps Python’s readable loop syntax while enforcing ownership and type rules at compile time. Iteration is usually borrowed: you can loop over a collection without consuming it.

For Loops

def total(values: list[int]) -> int:
    result: int = 0
    for value in values:
        result = result + value
    return result

The loop body sees each value as an int, and values remains usable after the loop.

Ranges

Use range for counted loops.

def factorial(n: int) -> int:
    result: int = 1
    for i in range(1, n + 1):
        result = result * i
    return result

Use enumerate when you need the index and the value together.

def label(items: list[str]) -> list[str]:
    result: list[str] = []
    for index, item in enumerate(items):
        result.append(str(index) + ": " + item)
    return result

Comprehensions

List and dictionary comprehensions keep their Python shape.

numbers: list[int] = [1, 2, 3, 4]
squares: list[int] = [n * n for n in numbers]
evens: list[int] = [n for n in numbers if n % 2 == 0]

labels: dict[str, int] = {f"n{n}": n for n in numbers}

The result type is checked from the expression and the declared binding.

Optional Values While Iterating

When a lookup can miss, handle None inside the loop before using the value.

def sum_known(users: list[str], scores: dict[str, int]) -> int:
    total: int = 0
    for user in users:
        score: int | None = scores[user]
        if score is not None:
            total = total + score
    return total

Mutation While Iterating

Prefer building a new collection when transforming data.

def positives(values: list[int]) -> list[int]:
    return [value for value in values if value > 0]

Mutating a collection while iterating over it is a place where ownership rules matter. Keep mutation outside the loop, or write into a separate result collection.

If you know Python, this is stricter by design. Mutating the collection you are iterating over is an ownership constraint the compiler can reject instead of a runtime surprise.

def doubled(values: list[int]) -> list[int]:
    result: list[int] = []
    for value in values:
        result.append(value * 2)
    return result

Next Steps

Values and Collections

Review the collection types that loops work with.

Ownership and Mutability

Learn when mutation needs mut, own, or own mut.

Get Started

Learn Sifr

CLI

Package Management

Standard Library

Concurrency

Error Codes

Iteration in Sifr

For Loops

Ranges

Comprehensions

Optional Values While Iterating

Mutation While Iterating

Next Steps

Values and Collections

Ownership and Mutability

​For Loops

​Ranges

​Comprehensions

​Optional Values While Iterating

​Mutation While Iterating

​Next Steps

Values and Collections

Ownership and Mutability

For Loops

Ranges

Comprehensions

Optional Values While Iterating

Mutation While Iterating

Next Steps