为了您的有趣任务，我决定实现相当复杂但通用的异步处理任何命令的解决方案。命令在cmds.txt 文件中提供，每行一个命令。现在只支持两个命令save 和exit。 save 可以在空格之后包含第二个可选参数，要保存到的文件名（默认为 save.txt）。
如果程序异常退出（未提供exit 命令），则工作将保存到临时文件save.txt.tmp。
cmds.txt 文件在单独的线程中处理，文件每秒检查一次，检查速度非常快，因此不占用 CPU，检查只是测试文件修改时间是否已更改。每个新命令都应添加到文件末尾的新行，不应删除已处理的行。在程序启动命令文件被清理。
主线程只检查has_cmds bool 变量（如果有新命令）它非常快并且可以经常完成，例如在处理 10-20 毫秒之类的最小任务之后。没有互斥体，因此所有的工作都非常快。
使用示例主线程在随机时间点产生任务处理的结果并将结果存储到数组中。在保存命令时，此结果数组保存为 JSON。
程序将有关其所做操作的所有信息打印到包含时间戳的控制台中。
接下来要测试程序：
- 启动程序。它立即开始处理计算工作。
- 在任何文本编辑器中打开
cmds.txt。
- 使用
save 字符串添加新行。保存文件。
- 程序应打印出
save 命令已被识别、处理并且工作已保存到文件save.txt。
- 在编辑器
save other.txt 中添加另一行。保存文件
- 程序应打印出已将工作保存到
save.txt。
- 添加新行
exit并保存。
- 程序应该退出。
- 再次尝试运行程序。
- 尝试在程序控制台中按
Ctrl+C。
- 程序应捕获此键盘中断并说明这一点，并将工作保存到临时文件
save.txt.tmp 并退出程序。
在最简单的情况下，为了节省键盘中断的工作，应该像in this answer那样完成。
您还可以通过像this solution 中处理 SIGINT 来优雅地实现进程终止。 SIGINT可以使用this program windows-kill发送给程序，语法windows-kill -SIGINT PID，其中PID可以通过microsoft's pslist获得。
import threading, random, os, json, time, traceback
cmds = []
has_cmds = False
cmds_fname = 'cmds.txt'
save_fname = 'save.txt'
save_fname_tmp = 'save.txt.tmp'
def CurTimeStr(*, exact = False):
from datetime import datetime
return (datetime.now(), datetime.utcnow())[exact].strftime(('[%H:%M:%S]', '[%Y-%m-%d %H:%M:%S.%f UTC]')[exact])
def Print(*pargs, **nargs):
print(CurTimeStr(), *pargs, flush = True, **nargs)
def AddCmd(c, *, processed = False):
global cmds, has_cmds
cmds.append({**{'processed': threading.Event()}, **c})
if processed:
cmds[-1]['processed'].set()
has_cmds = True
return cmds[-1]
def ExternalCommandsThread():
global cmds, has_cmds
Print('Cmds thread started.')
first, next_line, mtime = True, 0, 0.
while True:
try:
if first:
Print(f'Cleaning cmds file "{cmds_fname}".')
with open(cmds_fname, 'wb') as f:
pass
first = False
if os.path.exists(cmds_fname) and abs(os.path.getmtime(cmds_fname) - mtime) > 0.0001 and os.path.getsize(cmds_fname) > 0:
Print(f'Updated cmds file "{cmds_fname}". Processing lines starting from {next_line + 1}.')
with open(cmds_fname, 'r', encoding = 'utf-8-sig') as f:
data = f.read()
lines = list(data.splitlines())
try:
mtime = os.path.getmtime(cmds_fname)
for iline, line in zip(range(next_line, len(lines)), lines[next_line:]):
line = line.strip()
if not line:
continue
if line[0] not in ['[', '{', '"']:
cmd = line.split()
else:
cmd = json.loads(line)
pargs = []
if type(cmd) is list:
cmd, *pargs = cmd
cmd = {'cmd': cmd, 'pargs': pargs}
assert 'cmd' in cmd, 'No "cmd" in command line!'
c = cmd['cmd']
if c in ['save']:
assert len(set(cmd.keys()) - {'cmd', 'fname', 'pargs'}) == 0
AddCmd({'cmd': 'save', 'fname': cmd.get('fname', (cmd['pargs'] or [save_fname])[0])})
elif c == 'exit':
AddCmd({'cmd': 'exit'})
else:
assert False, f'Unrecognized cmd "{c}"!'
Print(f'Parsed cmd "{c}" on line {iline + 1}.')
next_line = iline + 1
except (json.decoder.JSONDecodeError, AssertionError) as ex:
traceback.print_exc()
Print(f'Failed to parse cmds line {iline + 1} with text "{line}"!')
except:
raise
for i, c in enumerate(cmds):
if c is None:
continue
if not c['processed'].is_set():
has_cmds = True
while not c['processed'].wait(10):
Print(f'Timed out waiting for cmd "{c["cmd"]}" to be processed, continuing waiting!')
Print(f'Processed cmd "{c["cmd"]}".')
cmds[i] = None
if c['cmd'] == 'exit':
Print('Exit cmd. Cmds thread finishes.')
return
has_cmds = False
time.sleep(1)
except Exception as ex:
traceback.print_exc()
Print(f'Exception ^^^^^ in Cmds thread!')
AddCmd({'cmd': 'exit'})
time.sleep(3)
def Main():
global cmds, has_cmds
Print('Main thread started.')
threading.Thread(target = ExternalCommandsThread, daemon = False).start()
results = []
def SaveWork(fname):
with open(fname, 'w', encoding = 'utf-8') as f:
f.write(json.dumps(results, ensure_ascii = False, indent = 4))
Print(f'Work saved to "{fname}".')
def ProcessCmds():
# Returns False only if program should exit
for c in cmds:
if c is None or c['processed'].is_set():
continue
if c['cmd'] == 'save':
SaveWork(c['fname'])
elif c['cmd'] == 'exit':
Print('Exit cmd. Main thread finishes...')
c['processed'].set()
return False
else:
assert False, 'Unknown cmd "c["cmd"]"!'
c['processed'].set()
return True
try:
# Main loop of tasks processing
for i in range(1000):
for j in range(10):
if has_cmds and not ProcessCmds(): # Very fast check if there are any commands
return # Exit
# Emulate small work of 0-200 ms long.
time.sleep(random.random() * 0.2)
# Store results of work in array
results.append({'time': CurTimeStr(exact = True), 'i': i, 'j': j})
assert False, 'Main finished without exit cmd!'
except BaseException as ex:
traceback.print_exc()
Print(f'Exception ^^^^^ in Main thread!')
SaveWork(save_fname_tmp)
AddCmd({'cmd': 'exit'}, processed = True)
if __name__ == '__main__':
Main()
示例输出 1：
[08:15:16] Main thread started.
[08:15:16] Cmds thread started.
[08:15:16] Cleaning cmds file "cmds.txt".
[08:15:21] Updated cmds file "cmds.txt". Processing lines starting from 1.
[08:15:21] Parsed cmd "save" on line 1.
[08:15:21] Work saved to "save.txt".
[08:15:21] Processed cmd "save".
[08:15:31] Updated cmds file "cmds.txt". Processing lines starting from 2.
[08:15:31] Parsed cmd "save" on line 2.
[08:15:31] Work saved to "other.txt".
[08:15:31] Processed cmd "save".
[08:15:35] Updated cmds file "cmds.txt". Processing lines starting from 3.
[08:15:35] Parsed cmd "exit" on line 3.
[08:15:35] Exit cmd. Main thread finishes...
[08:15:35] Processed cmd "exit".
[08:15:35] Exit cmd. Cmds thread finishes.
上面的输出对应的命令文件cmds.txt：
save
save other.txt
exit
示例输出 2：
[08:14:39] Main thread started.
[08:14:39] Cmds thread started.
[08:14:39] Cleaning cmds file "cmds.txt".
Traceback (most recent call last):
File "stackoverflow_64165394_processing_commands_in_prog.py", line 127, in Main
time.sleep(random.random() * 0.2)
KeyboardInterrupt
[08:14:40] Exception ^^^^^ in Main thread!
[08:14:40] Work saved to "save.txt.tmp".
[08:14:41] Processed cmd "exit".
[08:14:41] Exit cmd. Cmds thread finishes.
例子save.txt:
[
{
"time": "[2020-10-02 05:15:16.836030 UTC]",
"i": 0,
"j": 0
},
{
"time": "[2020-10-02 05:15:16.917989 UTC]",
"i": 0,
"j": 1
},
{
"time": "[2020-10-02 05:15:17.011129 UTC]",
"i": 0,
"j": 2
},
{
"time": "[2020-10-02 05:15:17.156579 UTC]",
"i": 0,
"j": 3
},
................