Python 【精】AttributeError: 'Module' object has no attribute 'STARTF_USESHOWINDOW'

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AttributeError: 'Module' object has no attribute 'STARTF_USESHOWINDOW' 

其它小伙伴好像都没遇到过，后来发现，应该是系统的问题，因为还出现了字节混乱的错误:
UNICODEENCODEERROR:‘ascii’ code can't encode...

这个先不提，我们先来看看下面的错误： STARTF_USESHOWINDOW

因公司信息，所以打上马赛克了。

百度了一会，发现网上解决方案都不靠谱。

出错原因：使用了subprocess模块，系统找不到这个模块。

你可以做个测试：在python下输出subprocess也会报这个错。

后来想到有可能系统环境的问题和模块代码引起，起初是替换了Lib\site-packages\matplotlib\compat下的subprocess.py，后来想到这是子模块，于是再替换了Lib\下的 subprocess.py ，再运行，一切正常。

国内外论坛都没找到相关的解释，后来去翻了源码才知道了原因，Cmd是WIN下命令符，pyc是编译后运行的，和JAVA一样，一次编译多处运行，如果出现这个错误的小伙伴可以找这几个地方替换下，或者直接拿可运行版本的丢进去覆盖下。

我们来翻看一下：

if mswindows:
    import threading
    import msvcrt
    import _subprocess
    class STARTUPINFO:
        dwFlags = 0
        hStdInput = None
        hStdOutput = None
        hStdError = None
        wShowWindow = 0
    class pywintypes:
        error = IOError
else:
    import select
    _has_poll = hasattr(select, 'poll')
    import fcntl
    import pickle

    # When select or poll has indicated that the file is writable,
    # we can write up to _PIPE_BUF bytes without risk of blocking.
    # POSIX defines PIPE_BUF as >= 512.
    _PIPE_BUF = getattr(select, 'PIPE_BUF', 512)

此处是引入了 import _subprocess 模块，也就是说 subprocess.py -> _subprocess

然后定位到：

if mswindows:
        #
        # Windows methods
        #

在这下面找到：

 def _execute_child(self, args, executable, preexec_fn, close_fds,
                           cwd, env, universal_newlines,
                           startupinfo, creationflags, shell, to_close,
                           p2cread, p2cwrite,
                           c2pread, c2pwrite,
                           errread, errwrite):
            """Execute program (MS Windows version)"""

            if not isinstance(args, types.StringTypes):
                args = list2cmdline(args)

            # Process startup details
            if startupinfo is None:
                startupinfo = STARTUPINFO()
            if None not in (p2cread, c2pwrite, errwrite):
                startupinfo.dwFlags |= _subprocess.STARTF_USESTDHANDLES
                startupinfo.hStdInput = p2cread
                startupinfo.hStdOutput = c2pwrite
                startupinfo.hStdError = errwrite

            if shell:
                startupinfo.dwFlags |= _subprocess.STARTF_USESHOWWINDOW
                startupinfo.wShowWindow = _subprocess.SW_HIDE
                comspec = os.environ.get("COMSPEC", "cmd.exe")
                args = '{} /c "{}"'.format (comspec, args)
                if (_subprocess.GetVersion() >= 0x80000000 or
                        os.path.basename(comspec).lower() == "command.com"):
                    # Win9x, or using command.com on NT. We need to
                    # use the w9xpopen intermediate program. For more
                    # information, see KB Q150956
                    # (http://web.archive.org/web/20011105084002/http://support.microsoft.com/support/kb/articles/Q150/9/56.asp)
                    w9xpopen = self._find_w9xpopen()
                    args = '"%s" %s' % (w9xpopen, args)
                    # Not passing CREATE_NEW_CONSOLE has been known to
                    # cause random failures on win9x.  Specifically a
                    # dialog: "Your program accessed mem currently in
                    # use at xxx" and a hopeful warning about the
                    # stability of your system.  Cost is Ctrl+C wont
                    # kill children.
                    creationflags |= _subprocess.CREATE_NEW_CONSOLE

看到这里，应该不难发现，CREATE_NEW_CONSOLE 是如何触发的。

再来看下main方法的测试入口：

"""
  KARL-Dujinyang
  QQ:309933706
"""
if __name__ == "__main__":
    if mswindows:
        _demo_windows()
    else:
        _demo_posix()

mswindows 在我们文章开头代码中已经提及了，测试的可以拿到此处代码进行测试：

mswindows = (sys.platform == "win32")

_demo_windows 方法的定义：

def _demo_windows():
    #
    # Example 1: Connecting several subprocesses
    #
    print "Looking for 'PROMPT' in set output..."
    p1 = Popen("set", stdout=PIPE, shell=True)
    p2 = Popen('find "PROMPT"', stdin=p1.stdout, stdout=PIPE)
    print repr(p2.communicate()[0])

    #
    # Example 2: Simple execution of program
    #
    print "Executing calc..."
    p = Popen("calc")
    p.wait()

可以看出，这里是由 OPEN->CLOSE 所引起的问题。如果出现这个错误的小伙伴可以找这几个地方替换下，或者直接拿可运行版本的丢进去覆盖下，也可以找我拿下源码覆盖，后面如果有时间我会上传到一份到CSDN上。

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