A strange behavior for isinstance method

Dear all,

Happy new year!

The isinstance method return diffrent value for a certain object with differenct conditions.

1. Create a 'point.py' file which contains a Point class:

class Point(): 
    def __init__(self, x=0, y=0): 
    self.x = x 
    self.y = y 

    def __str__(self): 
        return "({0},{1})".format(self.x, self.y) 

    def __add__(self, other): 
        print 'Type test inside: ' + str(isinstance(other, Point)) 
        print str(other) 
        x = self.x + other.x 
        y = self.y + other.y 
        return Point(x, y) 

    @staticmethod 
    def output(): 
    print 'Output test' 

#Run test in module 
print '-------------Test inside module ---------------' 
p1 = Point(2,3) 
p2 = Point(-1,2) 
print 'Type test outside: '+ str(isinstance(p2, Point)) 
p3 = p1 + p2 
print str(p2) 
Point.output()


2. Create a 'test_type.py' file to call the 'point' module:

import sys 
sys.path.append('D:/Working/MIScript/Jython/mis')   #You may change the path
import point 
from point import Point 
reload(point) 

#Run test 
print '-------------Test outside module ---------------' 
p1 = Point(2,3) 
p2 = Point(-1,2) 
print 'Type test outside: '+ str(isinstance(p2, Point)) 
p3 = p1 + p2 
print str(p2) 
Point.output()

The running result is:
-------------Test inside module --------------- 
Type test outside: True 
Type test inside: True 
(-1,2) 
(-1,2) 
Output test 
-------------Test outside module --------------- 
Type test outside: True 
Type test inside: False 
(-1,2) 
(-1,2) 
Output test 

I can not understand why the diffrence occured (with red color lines). Can anybody help me to expain it ? Thanks a lot!

By the way, I tested the diffrent version of Jython and also CPython 2.6 with same result.

Regards
Yaqiang


*************************************************
Dr. Yaqiang Wang
Chinese Academy of Meteorological Sciences (CAMS)
46, Zhong-Guan-Cun South Avenue
Beijing, 100081
China
　　　　　　　　　　　　　
[email protected]

http://www.meteothinker.com
**************************************************

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