[issue8198] Importing pydoc and overwriting sys.stdout, causes one char to be sent to the console when calling help()

[Daniel Diniz]

Daniel Diniz <ajaksu at gmail.com> added the comment:

Nice buglet, please take a look at Lib/pydoc.py to follow :)

As you point out, this is issue 1700304.
 
'plainpager', which outputs the help in these cases, uses 'sys.stdout.write(plain(text))', but Helper.help has a         "self.output.write('\n')" line that causes the behavior you see.

We could change "self.output.write('\n')" to "pager('\n')", but the real bug is that self.output is bound early to sys.stdout. So 'help()' is still redirecting to the old sys.stdout with your test.

I see a solution by turning Helper.output into a property, but it smells of over-engineering :) Passing all output to pagers should work too, unless we need Helper.output as a sort of sys.stderr.

The patch below shows that importing pydoc sets self.output prematurely and includes the "self.output.write('\n')" line.

Index: pydoc.py
===================================================================
--- pydoc.py    (revision 79447)
+++ pydoc.py    (working copy)
@@ -1765,6 +1765,7 @@
         elif isinstance(request, Helper): self()
         else: doc(request, 'Help on %s:')
         self.output.write('\n')
+        print >> sys.stderr, repr(self.output)

     def intro(self):
         self.output.write('''

----------
dependencies: +pydoc.help samples sys.stdout and sys.stdin at import time
keywords: +easy
nosy: +ajaksu2
priority:  -> low
stage:  -> test needed
type:  -> behavior

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue8198>
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