夫学须志也，才须学也，非学无以广才，非志无以成学。——诸葛亮
生活有度，自得慈铭 ——杜锦阳
今天新来的同事安装环境遇到个莫名其妙的问题：
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。
|| 版权声明：本文为博主杜锦阳原创文章
