import random


def create_random_string(length):
    """Create random string from a character set.
    
    Parameters
    ----------
    length : int
        Size of the expected string.
        
    Returns
    -------
    str
        Random string.

    Notes
    -----
    String is created from unambiguous letters.
    
    """
    return ''.join(random.choice("ACDEFGHJKMNPQRTWXYZ")
                     for _ in range(length)
                    )