def alpha(algorithm_period_return, treasury_period_return,
          benchmark_period_returns, beta):
    """
    http://en.wikipedia.org/wiki/Alpha_(investment)

    Args:
        algorithm_period_return (float):
            Return percentage from algorithm period.
        treasury_period_return (float):
            Return percentage for treasury period.
        benchmark_period_return (float):
            Return percentage for benchmark period.
        beta (float):
            beta value for the same period as all other values

    Returns:
        float. The alpha of the algorithm.
    """
    return algorithm_period_return - \
        (treasury_period_return + beta *
         (treasury_period_return - benchmark_period_returns))

###########################
# End Risk Metric Section #
###########################
dataset/ETHPy150Open quantopian/zipline/zipline/finance/risk/risk.py/alpha/swapped operands of `-`