matplotlib 条形图bar 缺少x

代码如下
import numpy as np
import matplotlib.pyplot as plt

            N = 5
            y = [20,10,30,25,15]

            index = np.arange(N)

            pl = plt.bar(left=index,height=y)
            plt.show()

            运行后 
             pl = plt.bar(left=index,height=y)
            TypeError: bar() missing 1 required positional argument: 'x'

plt.bar(x=index,height=y)