def get_param_val(
        param_str,
        param_key='',
        case_sensitive=False):
    """
    Extract numerical value from string information.
    This expects a string containing a single parameter.

    Parameters
    ==========
    name : str
        The string containing the information.
    param_key : str (optional)
        The string containing the label of the parameter.
    case_sensitive : bool (optional)
        Parsing of the string is case-sensitive.

    Returns
    =======
    param_val : int or float
        The value of the parameter.

    See Also
    ========
    set_param_val, parse_series_name

    """
    if param_str:
        if not case_sensitive:
            param_str = param_str.lower()
            param_key = param_key.lower()
        if param_str.startswith(param_key):
            param_val = param_str[len(param_key):]
        elif param_str.endswith(param_key):
            param_val = param_str[:-len(param_key)]
        else:
            param_val = None
    else:
        param_val = None
    return param_val