def natural(message, err='Please enter an integer greater than zero.', zero
    =False):
    """Command line input and error checking for natural numbers.

    Args:
        message (str): The input message displayed in the command line.
        err (str, optional): The message displayed for an erroneous input.
            Defaults to "Please enter an integer greater than zero.".
        zero (bool, optional): Zero status. True includes zero, False excludes
            zero. Defaults to False.

    Returns:
        int: The first sucessfully input natural number.
    """
    if zero:
        minimum = 0
    else:
        minimum = 1
    while True:
        data = input(message)
        data = data.strip()
        if data == '':
            print('Please provide an input.')
            continue
        if '.' in data:
            print(err)
            continue
        try:
            data = int(data)
        except ValueError:
            print(err)
            continue
        if data < minimum:
            print(err)
            continue
        return data
