def read_str_num(string, sep = None):
    """Returns a list of floats pulled from a string.
    
    Delimiter is optional; if not specified, uses whitespace.
    
    Parameters
    ----------
    string : str
        String to be parsed.
    sep : str, optional
        Delimiter (default is None, which means consecutive whitespace).
    
    Returns
    -------
    list of float
        Floats separated by `sep` in `string`.
    
    """
        
    # separate string into space-delimited strings of numbers
    num_str = string.split(sep)
    return [float(n) for n in num_str]