count_by()

Count instances in an array based on a function's result.

Implementation

Args: array: The array to count key_func: A function that returns a grouping key Returns: A dictionary of counts by key Raises: TypeError: If array is not iterable or key_func is not callable

Example

count_by([1, 2, 3], lambda x: x % 2)

Expected output: {0: 2, 1: 1}

Source Code

                        def count_by(array: List[T], key_func: Callable[[T], K]) -> dict:
    if not hasattr(array, "__iter__"):
        raise TypeError("The 'array' parameter must be iterable.")
    if not callable(key_func):
        raise TypeError("The 'key_func' parameter must be callable.")

    counts = {}
    for item in array:
        try:
            key = key_func(item)
            counts[key] = counts.get(key, 0) + 1
        except Exception:
            # Handle exceptions securely
            # Optionally log the exception without exposing sensitive information
            continue  # Skip elements that cause exceptions

    return counts
                    