今天會延續昨天做的事，然後嘗試使用感測機接收資料並且修改一下程式碼儲存至csv檔，以便進行後續的視覺化。

首先修改昨天的程式碼

import Adafruit_DHT
import time
import csv

sensor = Adafruit_DHT.DHT22

sensor_pin = 4

running = True

csvfile = "sensor_readings_1.csv"

while running:
    try:
    #read the humidity and temperature
        humidity, temperature = Adafruit_DHT.read_retry(sensor, sensor_pin)

        if humidity is not None and temperature is not None:
            humidity = round(humidity, 2)
            temperature = round(temperature, 2)
            print ('Temperature = {0:0.1f}*C  Humidity = {1:0.1f}%'.format(temperature, humidity))

        else:
            print('Failed to get reading. Try again!')

            
        timeC = time.strftime("%I")+':' +time.strftime("%M")+':'+time.strftime("%S")
        data = [temperature, timeC]

        with open(csvfile, "a") as output:
            writer = csv.writer(output, delimiter=",", lineterminator ='\n')
            writer.writerow(data)
        time.sleep(1)
        
    except KeyboardInterrupt:
        print ('Program stopped')

記得time.sleep可以自行設定更長的間隔，因為現在是實驗所以設為1秒。

接下來我們已經產出了csv檔，所以現在可以使用各種視覺化工具來畫圖，我們來用一個很常見的python matplotlib畫折線圖。

首先先安裝matplotlib

sudo apt-get install python3-matplotlib

再來編緝我們的程式碼

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import matplotlib.animation as animation
from datetime import datetime

fig = plt.figure()
rect = fig.patch
rect.set_facecolor('#fff8dc')
def animate(i):
    ftemp = 'sensor_readings_1.csv'
    fh = open(ftemp)
    temp = list()
    timeC = list()
    for line in fh:
        pieces = line.split(',')
        degree = pieces[0]
        timeB = pieces[1]
        
        ax = fig.add_subplot(1,1,1,facecolor='white')
        ax.plot(timeB, degree, 'o-', linewidth = 3.3)
        plt.ylabel('Temperature')
        plt.xlabel('Time')
        ani = animation.FuncAnimation(fig, animate, i  nterval = 6000)   
        plt.show()

然後再執行

python3 plot.py

這樣我們就會獲得折線圖了，如果觀察時間與間隔再拉長，就可以看出更明顯的一天氣溫差異了。