Table of Contents
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>>> class Sample:
def __enter__(self):
return self
def __exit__(self,type,value,trace):
print("type:",type)
print("value:",value)
print("trace:",trace)
def do_something(self):
bar = 1/0
return bar+10
>>> with Sample() as sample:
sample.do_something
type: <class 'ZeroDivisionError'>
value: division by zero
trace: <traceback object at 0x000001F067DD8FC8>
Traceback (most recent call last):
File "<pyshell#75>", line 2, in <module>
sample.do_something()
File "<pyshell#70>", line 9, in do_something
bar = 1/0
ZeroDivisionError: division by zero
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>>> class Sample:
def __enter__(self):
return self
def __exit__(self,type,value,trace):
print("type:",type)
print("value:",value)
print("trace:",trace)
return isinstance(value,ZeroDivisionError)
def do_something(self):
bar = 1/0
return bar+10
>>> with Sample() as sample:
sample.do_something()
type: <class 'ZeroDivisionError'>
value: division by zero
trace: <traceback object at 0x000001F067DE6348>
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>>> class Sample:
def __enter__(self):
bar = 1/0
return self
def __exit__(self,type,value,trace):
print("type:",type)
print("value:",value)
print("trace:",trace)
def do_something(self):
print("In do_something function")
>>>
>>> with Sample() as sample:
sample.do_something()
Traceback (most recent call last):
File "<pyshell#79>", line 1, in <module>
with Sample() as sample:
File "<pyshell#76>", line 3, in __enter__
bar = 1/0
ZeroDivisionError: division by zero
ÎÒ½« bar = 1/0 Õâ¾ä»áÅ׳öÒì³£µÄ´úÂëдÔÚ __enter__º¯ÊýÖУ¬µ«ÊÇͨ¹ý½á¹û¿ÉÒÔ·¢ÏÖ£¬__exit__º¯ÊýÒÔ¼°do__somthingº¯Êý²¢Ã»Óб»Ö´ÐУ¬ËùÒÔ˵Ã÷Ö´ÐÐ__enter__º¯ÊýʱÅ׳öÒì³£ºó´úÂë¾ÍÖжÏÁË£¬´Ó¶ø¿ÉÒÔµÃÖªÒì³£²¢Ã»Óб»²¶»ñ¡£
µ±È»£¬__exit__º¯ÊýÖгöÏÖÒì³£Ò²ÊÇÎÞ·¨²¶»ñµÄ
class Sample:
def __enter__(self):
print("In __enter__ function")
return self
def __exit__(self,type,value,trace):
print("In __exit__ function")
bar = 1/0
print("type:",type)
print("value:",value)
print("trace:",trace)
def do_something(self):
print("In do_something function")
>>> with Sample() as sample:
sample.do_something()
In __enter__ function
In do_something function
In __exit__ function
Traceback (most recent call last):
File "<pyshell#103>", line 2, in <module>
sample.do_something()
File "<pyshell#101>", line 7, in __exit__
bar = 1/0
ZeroDivisionError: division by zero
Èç¹ûûÓÐÒì³£µÄ»°£¬__exit__º¯ÊýÖеĺóÈý¸ö²ÎÊý»á±»´«ÈëNone
>>> class Sample:
def __enter__(self):
return self
def __exit__(self,type,value,trace):
print("type:",type)
print("value:",value)
print("trace:",trace)
def do_something(self):
print("In do_something function")
>>> with Sample() as sample:
sample.do_something()
In do_something function
type: None
value: None
trace: None
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