Question

This is probably something stupid I am missing but it has really got me hung up on a larger project (c extension) that I am writing.

Why is print "Hello, World!" passing None and an extra \n to sys.stdout here?

>>> import sys
>>> class StdOutHook:
...     def write(self, text):
...         sys.__stdout__.write("stdout hook received text: %s\n" % repr(text))
... 
>>> class StdErrHook:
...     def write(self, text):
...         sys.__stderr__.write("stderr hook received text: %s\n" % repr(text))
... 
>>> sys.stdout = StdOutHook()
>>> sys.stderr = StdErrHook()
>>> 
>>> def x():
...     print "Hello, World!"
... 
>>> 
>>> print x()
stdout hook received text: 'Hello, World!'
stdout hook received text: '\n'
stdout hook received text: 'None'
stdout hook received text: '\n'
>>> 

Answer 1

print x() prints the return value of x() which is implicitly None

Either replace print "Hello world" with return "Hello world" or replace print x() with x()