python - Python动画实时绘图从Mysql表中获取数据

Question

我正在尝试从表中读取最新行并在 python 中使用 animate 和 matplotlib 绘制图形。该表每 1 秒用一个新值更新一次。我需要通过实时绘制值来模拟图表。但是，当我使用间隔为 1 秒的 animate 函数时，每次获取间隔都会得到相同的值。

我正在添加代码供您参考。请让我知道我错过了什么。当我使用平面文件而不是 MySql 表时，相同的代码运行良好。

import matplotlib.pyplot as plt
import matplotlib.animation as animation
from matplotlib import style
import mysql.connector
import pandas as pd

style.use('fivethirtyeight')

mydb = mysql.connector.connect(
  host="xxxxxxxxxx",
  user="xxxxx",
  passwd="xxxxxxx",
  database="sakila"
)


fig = plt.figure(figsize=(8,5))
ax = plt.subplot2grid((1,1), (0,0))
plt.ion()
cursor = mydb.cursor()

def animate(i):

    df = pd.read_sql("SELECT * FROM DATA_TEST ORDER BY ID DESC LIMIT 1", mydb)
    y = df["VALUE"]
    x = df["ID"]
    xs = []
    ys = []
    xs.append(x)
    ys.append(float(y)*100)
    ax.clear()
    ax.plot(xs,ys)

ani = animation.FuncAnimation(fig, animate, interval=1000)
plt.show()


## TESTING CURSOR IN FOR LOOP
import mysql.connector
import pandas as pd
import time


mydb = mysql.connector.connect(
  host="xxxxxxx",
  user="xxxx",
  passwd="xxxxxx",
  database="xxxxx"
)



for i in range(10):
    cursor = mydb.cursor()

    cursor.execute("SELECT * FROM DATA_TEST ORDER BY ID DESC LIMIT 1")
    result = cursor.fetchall()
    print("Total rows are:  ", len(result))
    for j in result:
        print(j[0])
        print(j[1])
    time.sleep(10)
    cursor.close()