import numpy as np

data = [3, 5, 2, 8, 1, 9, 4, 7]
data_array = np.array(data)

from scipy.signal import find_peaks

# 计算波峰
# 注意 用 python3 !!!
peaks, _ = find_peaks(data_array)

# 索引值 array([1, 3, 5])
# peaks

# 计算波谷
# Numpy数组前加负号（-） ,表示取数组的逆序
valleys, _ = find_peaks(-data_array)
#  索引值 [2 4 6]
# valleys

import matplotlib.pyplot as plt

# 绘制原始数据
plt.plot(data_array)
# 标注波峰和波谷
plt.plot(peaks, data_array[peaks], "x", color='red')
plt.plot(valleys, data_array[valleys], "x", color='blue')
plt.show()