Python `print` 将额外的文本传递给 sys.stdout？

Question

这可能是我遗漏的一些愚蠢的东西，但它确实让我挂断了我正在编写的一个更大的项目(c 扩展名)。

为什么 print "Hello, World!" 将 None 和一个额外的 \n 传递给 sys.stdout 这里？

>>> 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() 打印 x() 的返回值，隐式为 None

将 print "Hello world" 替换为 return "Hello world" 或将 print x() 替换为 x()