Python 3写入管道 [英] Python 3 writing to a pipe

问题描述

我正在尝试编写一些代码以将数据放入管道，并且我希望该解决方案与python 2.6+和3.x兼容. 示例:

I'm trying to write some code to put data into a pipe, and I'd like the solution to be python 2.6+ and 3.x compatible. Example:

from __future__ import print_function

import subprocess
import sys

if(sys.version_info > (3,0)):
    print ("using python3")
    def raw_input(*prmpt):
        """in python3, input behaves like raw_input in python2"""
        return input(*prmpt)

class pipe(object):
    def __init__(self,openstr):
        self.gnuProcess=subprocess.Popen(openstr.split(),
                                         stdin=subprocess.PIPE)

    def putInPipe(self,mystr):
        print(mystr, file=self.gnuProcess.stdin)

if(__name__=="__main__"):
    print("This simple program just echoes what you say (control-d to exit)")
    p=pipe("cat -")
    while(True):
        try:
            inpt=raw_input()
        except EOFError:
            break
        print('putting in pipe:%s'%inpt)
        p.putInPipe(inpt)

上面的代码在python 2.6上有效，但在python 3.2上失败(请注意，上面的代码主要是使用2to3生成的-我只是为了使它与python 2.6兼容而稍微弄乱了.)

The above code works on python 2.6 but fails in python 3.2 (Note that the above code was mostly generated with 2to3 -- I just messed with it a little to make it python 2.6 compatible.)

Traceback (most recent call last):
  File "test.py", line 30, in <module>
   p.putInPipe(inpt)
  File "test.py", line 18, in putInPipe
   print(mystr, file=self.gnuProcess.stdin)
TypeError: 'str' does not support the buffer interface

我尝试了此处建议的字节函数(例如print(bytes(mystr，'ascii'))， TypeError:"str"不支持缓冲区接口 但这似乎不起作用. 有什么建议吗?

I've tried the bytes function (e.g. print(bytes(mystr,'ascii')) suggested here, TypeError: 'str' does not support the buffer interface But that doesn't seem to work. Any suggestions?

推荐答案

print函数将其参数转换为字符串表示形式，并将此字符串表示形式输出到给定文件.对于Python 2.x和Python 3.x，字符串表示形式始终为str类型.在Python 3.x中，管道仅接受bytes或缓冲区对象，因此这将不起作用. (即使将bytes对象传递给print，它也将转换为str.)

The print function converts its arguments to a string representation, and outputs this string representation to the given file. The string representation always is of type str for both, Python 2.x and Python 3.x. In Python 3.x, a pipe only accepts bytes or buffer objects, so this won't work. (Even if you pass a bytes object to print, it will be converted to a str.)

一种解决方案是改用write()方法(并在写入后刷新):

A solution is to use the write() method instead (and flushing after writing):

self.gnuProcess.stdin.write(bytes(mystr + "\n", "ascii"))
self.gnuProcess.stdin.flush()

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