Eryk Sun added the comment:
In 2.7, the _handle attribute is a _subprocess_handle object, which
automatically calls CloseHandle when deallocated. For example:
>>> p = subprocess.Popen('python -c "import time; time.sleep(120)"')
CreateProcess returns both the process handle and the thread handle. Python
doesn't use the thread handle, so it explicitly closes it by calling ht.Close():
Breakpoint 0 hit
KERNELBASE!CloseHandle:
00007ffb`a32fdf70 4883ec28 sub rsp,28h
0:000> kc 5
Call Site
KERNELBASE!CloseHandle
python27!sp_handle_close
python27!PyCFunction_Call
python27!call_function
python27!PyEval_EvalFrameEx
0:000> g
(IMO, it should skip this step if creationflags contains CREATE_SUSPENDED. The
thread handle makes it simpler to call ResumeThread.)
On the other hand, the process handle is deallocated implicitly when it's no
longer referenced:
>>> type(p._handle)
<type '_subprocess_handle'>
>>> hex(int(p._handle))
'0x164L'
>>> p.terminate()
>>> del p
Breakpoint 0 hit
KERNELBASE!CloseHandle:
00007ffb`a32fdf70 4883ec28 sub rsp,28h
0:000> kc 5
Call Site
KERNELBASE!CloseHandle
python27!sp_handle_dealloc
python27!dict_dealloc
python27!subtype_dealloc
python27!PyDict_DelItem
0:000> r rcx
rcx=0000000000000164
If the process handles aren't being closed in your case, then you're probably
keeping a reference to the Popen instances.
P.S. A Windows handle is not a "file descriptor". Kernel handles are user-mode
references to kernel objects. They aren't "files" unless the object happens to
be a File object. A process handle references a kernel Process object.
----------
nosy: +eryksun
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<http://bugs.python.org/issue28364>
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