[Python-Dev] Idle, site.py, and the release candidates

Antoine Pitrou solipsis at pitrou.net
Sun Mar 31 12:01:50 CEST 2013

On Sat, 30 Mar 2013 22:34:32 -0400
Terry Jan Reedy <tjreedy at udel.edu> wrote:
> I do not know enough about other circumstances in which stdin.fileno 
> would do something other than return 0 to be sure of what the proper fix 
> would be.
> (I increasingly dislike bare excepts as they hide the 
> thinking and knowledge of the original programmer.

You should learn to use the power of version control:

$ hg ann Lib/site.py

will tell you that the lines you mention come from the following

$ hg log -r 86358b43c8bb -vp
changeset:   44390:86358b43c8bb
parent:      44385:5670104acd39
user:        Christian Heimes <christian at cheimes.de>
date:        Mon Dec 31 03:07:24 2007 +0000
files:       Lib/site.py
Don't close sys.stdin with quit() if sys.stdin wraps fd 0. Otherwise it
will raise a warning: Lib/io.py:1221: RuntimeWarning: Trying to close
unclosable fd

diff --git a/Lib/site.py b/Lib/site.py
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -247,7 +247,12 @@
             # Shells like IDLE catch the SystemExit, but listen when
their # stdin wrapper is closed.
-                sys.stdin.close()
+                fd = -1
+                if hasattr(sys.stdin, "fileno"):
+                    fd = sys.stdin.fileno()
+                if fd != 0:
+                    # Don't close stdin if it wraps fd 0
+                    sys.stdin.close()
             raise SystemExit(code)

In this case the original motivation seems obsolete:

>>> import sys
>>> sys.stdin.fileno()
>>> sys.stdin.close()

That said, if IDLE users expect those global functions, perhaps IDLE
should define its own ones rather than rely on site.py.



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