63 lines
1.3 KiB
Python
63 lines
1.3 KiB
Python
class Resource():
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def __enter__(self):
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print('===connect to resource===')
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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print('===close resource connection===')
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print(exc_type)
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print(exc_val)
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print(exc_tb)
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return True
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def operate(self):
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1/0
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with Resource() as res:
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res.operate()
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import contextlib
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@contextlib.contextmanager
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def open_func(file_name):
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# __enter__方法
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print('open file:', file_name, 'in __enter__')
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file_handler = open(file_name, 'r')
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try:
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yield file_handler
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except Exception as exc:
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# deal with exception
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print('the exception was thrown')
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finally:
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print('close file:', file_name, 'in __exit__')
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file_handler.close()
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return
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with open_func('mytest.txt') as file_in:
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for line in file_in:
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1/0
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print(line)
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import contextlib
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@contextlib.contextmanager
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def open_func(file_name):
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# __enter__方法
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print('open file:', file_name, 'in __enter__')
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file_handler = open(file_name, 'r')
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# 【重点】：yield
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yield file_handler
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# __exit__方法
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print('close file:', file_name, 'in __exit__')
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file_handler.close()
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return
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with open_func('mytest.txt') as file_in:
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for line in file_in:
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print(line) |