Question

我有一个python脚本，它在raspberry pi 3的开头用一个守护进程启动。

这是我修改过的脚本，之前它运行得很好。该脚本从RFID阅读器获取卡的ID，然后在本地服务器上发布请求。

我修改了脚本只是为了在CSV文件中写入卡ID和日期。

当我手动运行脚本时，一切运行正常，它会将数据写入CSV并完美无缺。

但是当我重新启动覆盆子时，CSV文件中的写入不起作用。帖子请求有效。

我没有错误，无论如何脚本继续有效。

我不知道发生了什么。

这是我的剧本：

import requests
import binascii
import sys
import time
import subprocess
import Adafruit_PN532 as PN532
import csv
import datetime

duration = 20000
def post_url(uid, duration):
    url = 'http://localhost:1339/app=web/uid=%s/duration=%d' % (uid, duration)
    requests.post(url)
def get_url(uid, duration):
    url = 'http://localhost:1339/app=web/uid=%s/duration=%d' % (uid, duration)
    requests.get(url)

# RPI GPIO pins configuration
CS = 18
MOSI = 23
MISO = 24
SCLK = 25

# Create an instance of the PN532 class
pn532 = PN532.PN532(cs=CS, sclk=SCLK, mosi=MOSI, miso=MISO)

# Call beign to initialize communication with the PN532
pn532.begin()
pn532.SAM_configuration()

# Main loop to detect cards and read a block
with open('log.csv', 'a') as log:

    while True:
        # Check if a card is available to read
        uid = pn532.read_passive_target()
        # Try again if no card is available
        if uid is None:
            continue
        # Transforming card ui into hex format for comparison against
        # registereed uid cards
        card_uid = '0x{0}'.format(binascii.hexlify(uid))
        if card_uid is not None:
            subprocess.call("date")
            print('Hello')

            writer = csv.writer(log)
            data=[card_uid, datetime.datetime.now()]
            writer.writerow([data[0], date[1]])

            post_url(card_uid, duration)
            time.sleep(5)
        else:
            continue

.sh文件：

DIR=my/path/to/file
DAEMON=$DIR/card_read.py
DAEMON_NAME=card_read
# Add any command line options for your daemon here
DAEMON_OPTS=""
# This next line determines what user the script runs as.
# Root generally not recommended but necessary if you are using the Raspberry Pi GPIO from Python.
DAEMON_USER=root
# The process ID of the script when it runs is stored here:
PIDFILE=/var/run/$DAEMON_NAME.pid
. /lib/lsb/init-functions
do_start () {
    log_daemon_msg "Starting system $DAEMON_NAME daemon"
    start-stop-daemon --start --background --pidfile $PIDFILE --make-pidfile --user $DAEMON_USER --chuid $DAEMON_USER --startas $DAEMON -- $DAEMON_OPTS
    log_end_msg $?
}
do_stop () {
    log_daemon_msg "Stopping system $DAEMON_NAME daemon"
    start-stop-daemon --stop --pidfile $PIDFILE --retry 10
    log_end_msg $?
}
case "$1" in
    start|stop)
        do_${1}
        ;;
    restart|reload|force-reload)
        do_stop
        do_start
        ;;
    status)
        status_of_proc "$DAEMON_NAME" "$DAEMON" && exit 0 || exit $?
        ;;
    *)
        echo "Usage: /etc/init.d/$DAEMON_NAME {start|stop|restart|status}"
        exit 1
        ;;
esac
exit 0

Answer 1

不要打开文件一次，请尝试等待，直到有东西要写，然后只在写入期间保持文件打开。这将强制缓冲区刷新到磁盘，允许您tail -f并实时查看数据。像这样：

while True:
    uid = pn532.read_passive_target()
    if uid is not None:
        record(uid)
        time.sleep(5)

def record(uid):
    card_uid = '0x{0}'.format(binascii.hexlify(uid))
    with open('log.csv', 'a') as log:
        writer = csv.writer(log)
        writer.writerow([card_uid, datetime.datetime.now()])
    post_url(card_uid, duration)

Python CSV不在守护进程上工作，但在手动启动时有效

1 个答案: