python脚本在手动启动时打印到txt，但不是在启动时通过rc.local在启动时打印

Question

我正在尝试让我的树莓派将数据从外部传感器打印到显示器并同时将其保存为 .txt。

通过 ssh 在 shell 中启动脚本时，我所做的工作正常。但这会在关闭 shell 后停止脚本。

所以我尝试将它放在 rc.local 文件中以在启动时启动它。但这只是半途而废，因为它会在显示屏上显示数据，但不会将其保存到文件中。

import grovepi

from grovepi import *
from grove_rgb_lcd import *
from time import sleep, strftime
from math import isnan


#port definition
dht_sensor_port = 7 
dht_sensor_type = 0 
led_green = 5
led_red = 6
f = open("hwd.txt", "w")

#rgb display color
setRGB(0,255,0)

while True:
    try:
        [ temp,hum ] = dht(dht_sensor_port,dht_sensor_type)
        print("temp =", temp, "C\thumidity =", hum,"%")
        print("{0},{1}\n".format(strftime("%Y-%m-%d %H:%M:%S"),(temp,hum)), file=f)

        if isnan(temp) is True or isnan(hum) is True:
            raise TypeError('nan error')

        t = str(temp)
        h = str(hum)    
        
        setText_norefresh("Temp:" + t + "C\n" + "Humidity :" + h + "%")

        if hum < 40.0 or hum > 60.0:
            grovepi.digitalWrite(led_red,1)
            grovepi.digitalWrite(led_green,0)
        else:
            grovepi.digitalWrite(led_green,1)
            grovepi.digitalWrite(led_red, 0)

    except (IOError, TypeError) as e:
        print(str(e))
        setText("")

    except KeyboardInterrupt as e:
        print(str(e))
        setText("")
        break

    sleep(1)

``

Answer 1

您正在运行一个无限循环，因此您需要关闭文件流以将更改保存到您的文件中。如果您在没有循环的情况下运行脚本，您可以看到即使没有关闭 Steam，更改也会保存，这是因为它隐式处理。因此，您需要打开和关闭文件流，这可以使用 with 关键字轻松完成。我认为下面的代码很适合你。

import grovepi

from grovepi import *
from grove_rgb_lcd import *
from time import sleep, strftime
from math import isnan

# port definition
dht_sensor_port = 7
dht_sensor_type = 0
led_green = 5
led_red = 6

# rgb display color
setRGB(0, 255, 0)

while True:
    try:
        [temp, hum] = dht(dht_sensor_port, dht_sensor_type)
        print("temp =", temp, "C\thumidity =", hum, "%")
        with open("hwd.txt", "w") as f:
            print("{0},{1}\n".format(strftime("%Y-%m-%d %H:%M:%S"), (temp, hum)), file=f)

        if isnan(temp) is True or isnan(hum) is True:
            raise TypeError('nan error')

        t = str(temp)
        h = str(hum)

        setText_norefresh("Temp:" + t + "C\n" + "Humidity :" + h + "%")

        if hum < 40.0 or hum > 60.0:
            grovepi.digitalWrite(led_red, 1)
            grovepi.digitalWrite(led_green, 0)
        else:
            grovepi.digitalWrite(led_green, 1)
            grovepi.digitalWrite(led_red, 0)

    except (IOError, TypeError) as e:
        print(str(e))
        setText("")

    except KeyboardInterrupt as e:
        print(str(e))
        setText("")
        break

    sleep(1)