pydoc.help (aliased to the builtin help) uses the values of sys.stdout and sys.stdin that were in use when the pydoc module was imported.  This means that if sys.stdout and/or sys.stdin are later modified, subsequent calls to pydoc.help (or help) use the wrong stdout and stdin.

Instead, help should use the current values of sys.stdout and sys.stdin each time it is called.

Reported against Python 2.4.4.

issue8198 is related.

Re. 1700304, it's easy to work around by writing

from pydoc import help
import sys
help.output = sys.stdout
help.input = sys.stdin

From #8198:

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.

Duplicate of #8198.