Python の systemd service のファイルIO

Raspbian 上で動く Systemd Service を Python でログを取りたいときのメモ．
Raspbian に限った話ではないかもしれない．

.service ファイル

logwrite.service

[Unit]
Description = Log write test

[Service]
ExecStart = path/to/main.py

[Install]
WantedBy = multi-user.target

ファイルに書いてくれないコード

※ Systemd Service として実行しなければ（python3 main.py などとすれば）このコードでも書き込める．

main.py

#!/usr/bin/python3

from writer import LogWriter


if __name__ == '__main__':
    writer = LogWriter('path/to/logfile')
    writer.write('foo')
    writer.write('bar')
    writer.write('baz')
    writer.close()

writer.py

import csv
import time


TIME_FORMAT = '%y/%m/%d;%H:%M:%S'


class LogWriter:
    def __init__(self, path):
        self.logfile = open(path, 'a')
        self.writer = csv.writer(self.logfile, lineterminator='\n')

    def write(self, data):
        self.writer.writerow([time.strftime(TIME_FORMAT), data])

    def close(self):
        self.logfile.close()

ファイルに書いてくれるコード

main.py で open した．

main.py

#!/usr/bin/python3

from writer import LogWriter


if __name__ == '__main__':
    logfile = open('path/to/logfile', 'a')
    writer = LogWriter(logfile)
    writer.write('foo')
    writer.write('bar')
    writer.write('baz')
    writer.close()

writer.py

import csv
import time


TIME_FORMAT = '%y/%m/%d;%H:%M:%S'


class LogWriter:
    def __init__(self, logfile):
        self.logfile = logfile
        self.writer = csv.writer(logfile, lineterminator='\n')

    def write(self, data):
        self.writer.writerow([time.strftime(TIME_FORMAT), data])

    def close(self):
        self.logfile.close()