filter.py 文件源码

def _check_method(method, iir_params, extra_types):
    """Helper to parse method arguments"""
    allowed_types = ['iir', 'fft'] + extra_types
    if not isinstance(method, string_types):
        raise TypeError('method must be a string')
    if method not in allowed_types:
        raise ValueError('method must be one of %s, not "%s"'
                         % (allowed_types, method))
    if method == 'iir':
        if iir_params is None:
            iir_params = dict(order=4, ftype='butter')
        if not isinstance(iir_params, dict):
            raise ValueError('iir_params must be a dict')
    elif iir_params is not None:
        raise ValueError('iir_params must be None if method != "iir"')
    method = method.lower()
    return iir_params