我有一个调用外部程序的Python脚本(sox
是准确的)。现在我必须用sox
做几件事,但总是要等到一个文件完成写入,所以我可以在下一个命令中将它用作输入文件。
subprocess.wait()
不起作用,因为sox
的执行将完成,但文件不会写完。
这是我的代码:
import tempfile
import shlex
file_url = '/some/file.wav'
out_file = 'some/out.wav'
tmp_file = tempfile.NamedTemporaryFile()
pad_cmd = 'sox ' + file_url + ' ' + tmp_file.name + ' pad 0.0 3.0'
subprocess.call(shlex.split(pad_cmd))
trim_cmd = 'sox ' + tmp_file.name + ' -t wav ' + out_file + ' trim 0.0 3.0'
任何等待文件完成写入tmp_file.name
而不使用等待一段固定时间的计时器的方法。或者sox
中是否有内置方式将输出文件用作输入?特殊文件名-
不适用于pad
和trim
。
答案 0 :(得分:2)
如果sox
works with stdin/stdout:
#!/bin/sh
sox input.wav -t wav - pad 0.0 3.0 | sox -t wav - out.wav trim 0.0 3.0
然后你可以用Python编写它:
#!/usr/bin/env python
from subprocess import Popen, PIPE
pad = Popen(["sox", "input.wav", "-t", "wav", "-", "pad", "0.0", "3.0"],
stdout=PIPE)
trim = Popen(['sox', '-t', 'wav', '-', 'out.wav', 'trim', '0.0', '3.0'],
stdin=pad.stdout)
pad.stdout.close() # notify pad on write if trim dies prematurely
pipestatus = [p.wait() for p in [pad, trim]]
注意:如果您不使用不受信任的输入来构造命令,那么您可以将它们作为单行传递以便于阅读(在这种情况下,shell会创建管道):
#!/usr/bin/env python
from subprocess import check_call
cmd = "sox input.wav - -t wav pad 0.0 3.0 | sox - -t wav out.wav trim 0.0 3.0"
check_call(cmd, shell=True)
如果你不能写入/读取stdout / stdin,那么你可以尝试命名管道,以避免等待文件:
#!/bin/sh
mkfifo /tmp/sox.fifo
sox /tmp/sox.fifo -t wav out.wav trim 0.0 3.0 & # read from fifo
sox input.wav /tmp/sox.fifo pad 0.0 3.0 # write to fifo
或在Python中相同:
#!/usr/bin/env python
from subprocess import Popen, check_call
with named_pipe() as path:
trim = Popen(["sox", path, '-t', 'wav', 'out.wav', 'trim', '0.0', '3.0'])
check_call(["sox", "input.wav", path, "pad", "0.0", "3.0"]) # pad
rc = trim.wait()
其中named_pipe()
定义为:
import os
from contextlib import contextmanager
from shutil import rmtree
from tempfile import mkdtemp
@contextmanager
def named_pipe():
dirname = mkdtemp()
try:
path = os.path.join(dirname, 'named_pipe')
os.mkfifo(path)
yield path
finally:
rmtree(dirname)
答案 1 :(得分:1)
您可以等待文件,然后才能阅读:
handle = open(tmp_file.name)
from subprocess import select
select.select([handle], [], [])