[英]How to wildly and/or alternatingly read from stdout and/or stderr and write to stdin of a process in python?
我在这里搜索了很多不同的问题和答案，但我没有找到一个通用的方法：
此处可找到的大多数示例仅将 ONCE 写入 stdin，而从 stdout 和/或 stderr 仅读取 ONCE（之前/之后）。 我的意图是“编织”从标准输出和/或标准错误读取并写入标准输入！ 这里有一个例子：
python3.exe>>>print('Hello World.')\nHello World.\n ）并从标准输出阅读>>>x = [6, 0]\n>>>y = x[0] / x[1]\nZeroDivisionError: division by zero ）我试图用这个找到的互联网示例来解决它（在其他失败的尝试之后）：
# Example #27
# of https://www.programcreek.com/python/example/85342/asyncio.create_subprocess_shell
# Source Project: Python-Journey-from-Novice-to-Expert Author: PacktPublishing File: 07_processes.py License: MIT License 5 votes vote downvote up
import asyncio
import sys
async def read_from_pipe(pipe, buf, timeout_sec):
while True:
try:
pipe_byte = await asyncio.wait_for(pipe.read(1), timeout_sec)
except asyncio.TimeoutError:
break
else:
if len(pipe_byte) == 1:
buf.append(pipe_byte[0])
else:
pipe_byte == b'\n' # in case of end of file: fake end of line
if pipe_byte == b'\n':
return len(buf)
async def run_script(version):
process = await asyncio.create_subprocess_shell(
r'C:\Programs\Python\Python38-32\python.exe',
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE,
stdin=asyncio.subprocess.PIPE,
)
if version == 0:
# Write a simple Python script to the interpreter
process.stdin.write(b'\n'.join((
b'import math',
b'x = 2 ** 8',
b'y = math.sqrt(x)',
b'z = math.sqrt(y)',
b'print("x: %d" % x)',
b'print("y: %d" % y)',
b'print("z: %d" % z)',
b'for i in range(int(z)):',
b' print("i: %d" % i)',
)))
# Make sure the stdin is flushed asynchronously
await process.stdin.drain()
# And send the end of file so the Python interpreter will
# start processing the input. Without this the process will
# stall forever.
process.stdin.write_eof()
# Fetch the lines from the stdout asynchronously
async for out in process.stdout:
# Decode the output from bytes and strip the whitespace
# (newline) at the right
print(out.decode('utf-8').rstrip())
# Wait for the process to exit
await process.wait()
elif version == 1:
cmds = [b'import math',
b'x = 2 ** 8',
b'y = math.sqrt(x)',
b'z = math.sqrt(y)',
# b'q = z / 0',
b'print("x: %d" % x)',
b'print("y: %d" % y)',
b'print("z: %d" % z)',
b'for i in range(int(z)):',
b' print("i: %d" % i)',
b'exit(0)',
]
idx = 0
while True:
stdout_buf = bytearray(b'')
out_read = await read_from_pipe(process.stdout, stdout_buf, 0.5)
print(f'stdout[{out_read}]: {stdout_buf.decode("ascii")}\n') if out_read else None
stderr_buf = bytearray(b'')
err_read = await read_from_pipe(process.stderr, stderr_buf, 0.5)
print(f'stderr[{err_read}]: {stdout_buf.decode("ascii")}\n') if err_read else None
if idx < len(cmds):
current_cmd = cmds[idx].decode('ascii')
print(f'writing command at index {idx}: "{current_cmd}"')
process.stdin.write(cmds[idx])
process.stdin.write(b'\n')
await process.stdin.drain()
process.stdin.write_eof() # tried with/without this line, afterwards program hangs
idx += 1
else:
break
await process.wait()
if sys.platform == "win32":
codepage = 'cp437'
loop = asyncio.ProactorEventLoop() # For subprocess' pipes on Windows
asyncio.set_event_loop(loop)
else:
codepage = 'utf-8'
loop = asyncio.get_event_loop()
version = 1 # version = 0 runs but is not alternatingly reading stdout/stderr and writing to stdin!
returncode = loop.run_until_complete(run_script(1))
print(f'done with return code = {returncode}.')
目前它不会从stdout和stderr读取任何内容。 并且在cmds中的条目写入后，程序也会挂起。 最后它应该在 linux 下运行。
如何正确编写程序？
python3.exe 是不是一个“太特殊”的命令行工具，是这些问题的根本原因吗？
提示：这个例子和解决方案根本不必是高性能的。 用于控制的预期命令行工具非常慢（总体执行时间为 20 秒到 20 分钟）。 如果（简化的）工作解决方案不需要多线程和多处理，则实际上并不需要多线程和多处理。
我发现python3.exe有点太特殊了，无法控制。 我最好在 windows 上使用例如cmd /S （我为 Linux 阅读了/bin/bash ） - 现在可以使用：
# Example #27
# of https://www.programcreek.com/python/example/85342/asyncio.create_subprocess_shell
# Source Project: Python-Journey-from-Novice-to-Expert Author: PacktPublishing File: 07_processes.py License: MIT License 5 votes vote downvote up
import asyncio
import sys
async def read_from_pipe(pipe, buf, timeout_sec):
while True:
try:
pipe_byte = await asyncio.wait_for(pipe.read(1), timeout_sec)
except asyncio.TimeoutError:
return len(buf) # no more bytes available currently on that pipe
else:
if len(pipe_byte) == 1:
buf.append(pipe_byte[0])
else:
return len(buf) # end of pipe reached
async def run_script():
process = await asyncio.create_subprocess_shell(
'cmd /S',
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE,
stdin=asyncio.subprocess.PIPE,
)
cmds = [b'dir P*C*S*.*',
b'echo %temp%',
b'exit']
idx = 0
while True:
stdout_buf = bytearray(b'')
out_read = await read_from_pipe(process.stdout, stdout_buf, 0.5)
print(f'stdout[{out_read}]: {stdout_buf.decode("ascii")}\n') if out_read else None
stderr_buf = bytearray(b'')
err_read = await read_from_pipe(process.stderr, stderr_buf, 0.5)
print(f'stderr[{err_read}]: {stdout_buf.decode("ascii")}\n') if err_read else None
if idx < len(cmds):
current_cmd = cmds[idx].decode('ascii')
print(f'writing command at index {idx}: "{current_cmd}"')
process.stdin.write(cmds[idx])
process.stdin.write(b'\n')
await process.stdin.drain()
idx += 1
else:
pass
if process.returncode is not None:
print(f'return code = {process.returncode}')
return process.returncode
if sys.platform == "win32":
codepage = 'cp437'
loop = asyncio.ProactorEventLoop() # For subprocess' pipes on Windows
asyncio.set_event_loop(loop)
else:
codepage = 'utf-8'
loop = asyncio.get_event_loop()
returncode = loop.run_until_complete(run_script())
print(f'done with return code = {returncode}.')
output 在我的电脑上：
PS C:\Git\ownPythonRepository\Python\CliTap> c:; cd 'c:\Git\ownPythonRepository\Python\CliTap'; & 'C:\Programs\Python\Python38-32\python.exe' 'c:\Users\BitLauncher\.vscode\extensions\ms-python.python-2022.14.0\pythonFiles\lib\python\debugpy\adapter/../..\debugpy\launcher' '63136' '--' 'c:\Git\ownPythonRepository\Python\CliTap\PythonConsoleSandbox.py'
stdout[137]: Microsoft Windows [Version 10.0.11111.2222]
(c) Microsoft Corporation. All rights reserved.
C:\Git\ownPythonRepository\Python\CliTap>
stdout[340]: dir P*C*S*.*
Volume in drive C is What
Volume Serial Number is 9999-9999
Directory of C:\Git\ownPythonRepository\Python\CliTap
2022-09-26 23:52 2,365 PythonConsoleSandbox.py
1 File(s) 2,365 bytes
0 Dir(s) 99,999,999,999 bytes free
C:\Git\ownPythonRepository\Python\CliTap>
writing command at index 1: "echo %temp%"
stdout[93]: echo %temp%
C:\Users\BitLau~1\AppData\Local\Temp
C:\Git\ownPythonRepository\Python\CliTap>
writing command at index 2: "exit"
stdout[5]: exit
return code = 1
done with return code = 1.
PS C:\Git\ownPythonRepository\Python\CliTap>
就是这样 - 现在我将能够根据 stdout 和/或 stderr 特定命令向 stdin 写入......太好了。 稍后我可以通过多线程改进它:-) 如果需要。
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