def read_lines_decimal(read_file):
    """
    Read all lines of a file that are decimal values into a list.
    :param read_file: File handler for the file to read.
    :return: List of decimal values.
    """
    # Read all lines with decimal values into list.
    data_list = []
    for line in read_file:
        # Strip whitespace from line
        value = str.strip(line)
        # Try converting to floating point. If successful, add to list of numbers.
        try:
            data_list.append(float(value))
        # Do nothing if line is not decimal
        except ValueError:
            pass
    return data_list