对Python2与Python3中__bool__方法的差异详解

class Demo():

def __init__(self,value = 0):

  self.value = value

def __bool__(self):

  return bool(self.value > 5)


obj = Demo()

obj.value = 0

if obj:

print(\"yes\")

else:

print(\"no\")

print(bool(obj))

grey@DESKTOP-3T80NPQ:/mnt/e/01_workspace/02_programme_language/03_python/03_OOP/2017/08/16$python bool_demo.py

yes

True

grey@DESKTOP-3T80NPQ:/mnt/e/01_workspace/02_programme_language/03_python/03_OOP/2017/08/16$python -V

Python 2.7.6

E:\\01_workspace\\02_programme_language\\03_python\\03_OOP\\2017\\08\\16>pythonbool_demo.py

no

False


E:\\01_workspace\\02_programme_language\\03_python\\03_OOP\\2017\\08\\16>python-V

Python 3.6.0