取最大最小值 np.where要比df.max要快很多

%%timeit
stgg=np.where(df['close']>df['open'],df['close'],df['open'])
stdd=np.where(df['close']<df['open'],df['close'],df['open'])
#196 µs ± 1.72 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

%%timeit
stgg = df[['open', 'close']].max(axis=1)
stdd = df[['open', 'close']].min(axis=1)
#599 µs ± 6.93 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)