Fix Windows compatibility: replace platform-specific num_fds() with runtime check

[Copilot]

Arachnado crashes on Windows with AttributeError: 'Process' object has no attribute 'num_fds'. The psutil library provides num_fds() only on Unix/Linux/macOS, while Windows uses num_handles().

Changes

• arachnado/process_stats.py: Replace direct num_fds() call with runtime method detection using hasattr()
  • Try num_fds() first (Unix/Linux/macOS)
  • Fall back to num_handles() (Windows)
  • Return None if neither exists
• CHANGES.rst: Document the fix

Before/After

# Before - crashes on Windows
'num_fds': self.process.num_fds(),

# After - works cross-platform
num_fds = None
if hasattr(self.process, 'num_fds'):
    num_fds = self.process.num_fds()
elif hasattr(self.process, 'num_handles'):
    num_fds = self.process.num_handles()

'num_fds': num_fds,

Note: The second error in the issue (singledispatch/DeferredList.__mro__) is a Python 2.7 compatibility issue resolved in Python 3+.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Can't run arachnado </issue_title> <issue_description>I use annacoda27 for Windows 64-bit and my machine is Windows 10 pro.

When I type arachnado in CMD And this is an issue like that:

2017-03-10 11:57:28 [tornado.application] ERROR: Exception in callback <bound method ProcessStatsMonitor._emit of <arachnado.process_stats.ProcessStatsMonitor object at 0x00000000041854A8>> Traceback (most recent call last): File "c:\users\king\anaconda2\lib\site-packages\tornado\ioloop.py", line 1041, in _run return self.callback() File "c:\users\king\anaconda2\lib\site-packages\arachnado\process_stats.py", line 61, in _emit 'num_fds': self.process.num_fds(), AttributeError: 'Process' object has no attribute 'num_fds'

This information refresh per second

When I stop arachnado some infomations come out

2017-03-10 11:57:33 [scrapy.crawler] INFO: Received SIGINT, shutting down gracefully. Send again to force 2017-03-10 11:57:33 [tornado.application] ERROR: Exception in callback <functools.partial object at 0x0000000004247188> Traceback (most recent call last):Traceback (most recent call last): File "c:\users\king\anaconda2\lib\site-packages\tornado\ioloop.py", line 612, in _run_callback ret = gen.convert_yielded(ret) File "c:\users\king\anaconda2\lib\site-packages\singledispatch.py", line 210, in wrapper return dispatch(args[0].__class__)(*args, **kw) File "c:\users\king\anaconda2\lib\site-packages\singledispatch.py", line 191, in dispatch impl = _find_impl(cls, registry) File "c:\users\king\anaconda2\lib\site-packages\singledispatch.py", line 142, in _find_impl mro = _compose_mro(cls, registry.keys()) File "c:\users\king\anaconda2\lib\site-packages\singledispatch.py", line 98, in _compose_mro bases = set(cls.__mro__) AttributeError: class DeferredList has no attribute '__mro__'

I don't know what happend in the code.

Could you help me to point it out ?

Best wishes</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes TeamHG-Memex/arachnado#32

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