为什么我的并行代码会产生错误？

Question

问题1: 当sys.stdout.write未被包含在单独的函数中时，下面的代码会失败。

问题2: 当sys.stdout.write被包含在单独的函数中时，代码会在每个字母之间打印空格。

代码（v1）：

#!/usr/bin/env python

import pp
import sys

def main():
    server = pp.Server()

    for c in "Hello World!\n":
        server.submit(sys.stdout.write, (c,), (), ("sys",))()

if __name__=="__main__":
    main()

追踪:

$ ./parhello.py
Traceback (most recent call last):
  File "./parhello.py", line 15, in <module>
    main()
  File "./parhello.py", line 12, in main
    server.submit(write, (c,), (), ("sys",))()
  File "/Library/Python/2.7/site-packages/pp.py", line 461, in submit
    sfunc = self.__dumpsfunc((func, ) + depfuncs, modules)
  File "/Library/Python/2.7/site-packages/pp.py", line 639, in __dumpsfunc
    sources = [self.__get_source(func) for func in funcs]
  File "/Library/Python/2.7/site-packages/pp.py", line 706, in __get_source
    sourcelines = inspect.getsourcelines(func)[0]
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/inspect.py", line 688, in getsourcelines
    lines, lnum = findsource(object)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/inspect.py", line 527, in findsource
    file = getsourcefile(object)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/inspect.py", line 446, in getsourcefile
    filename = getfile(object)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/inspect.py", line 422, in getfile
    'function, traceback, frame, or code object'.format(object))
TypeError: <built-in method write of file object at 0x1002811e0> is not a module, class, method, function, traceback, frame, or code object
make: *** [test] Error 1

代码（v2）：

#!/usr/bin/env python

import pp
import sys

def hello(c):
    sys.stdout.write(c)

def main():
    server = pp.Server()

    for c in "Hello World!\n":
        server.submit(hello, (c,), (), ("sys",))()

if __name__=="__main__":
    main()

追踪：

$ ./parhello.py
H e l l o   W o r l d !

- mcandre

Answer 1

首先，pp 并不支持将内置函数作为参数传递给submit。第二个问题更加复杂。在 pp 调用提交的函数之前，它会重定向 stdout 和 stderr 到一个 StringIO 对象上。完成任务后，它会打印来自 StringIO 对象的值。

print sout,

这意味着在打印之前，它会将一个空格附加到sout的内容。为了避免这种情况，请不要让您的函数直接使用sys.stdout，而是将其打印到文件或您管理的队列中，并以更好的方式处理打印。

- Abe Karplus