导入的模块打印出无

Question

I am not sure if anyone asked this already but I could not find was I was looking for, so here we go. I have created a module named xxx.py. This is whats inside:

class A(object):
     def aaa(self):
        print "Ahaaaa!!!!!!!!!!!!!!!"

Also I have another script ex45.py:

from xxx import A

xxx = A()
print xxx.aaa()

When I run python ex45.py I get the following:

PS E:\python\ex\ex45> python ex45.py
Ahaaaa!!!!!!!!!!!!!!!
None

Why is there that 'None'???

My purpouse is to write multipe scripts where I create classes that I want to use in another script. I am sure there are better ways to code but I am now learning python and I want to understand how everything works.

PS: I am using python 2.7.9. and learning from the book Learn Python the hard way.

Answer 1

It's because your aaa() method returns None . Sou you print out something and then you also print out the returned value. Try this:

from xxx import A

xxx = A()
xxx.aaa()

And this (one at time):

class A(object):
     def aaa(self):
         return "Ahaaaa!!!!!!!!!!!!!!!"

And see what happens.

Answer 2

The aaa method prints out "Ahaaaa!!!!!!!!!!!!!!!" and returns nothing (in Python what doesn't return anything actually returns None ). Then, in ex45.py you print the return value of aaa , which is None .

To solve the problem, you may either do xxx.aaa() (without print ing), or in the aaa method return "Ahaaaa!!!!!!!!!!!!!!!" instead of print ing it.