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  1. import functools
  2. import sys
  3.  
  4. def file_reader(func):
  5.     @functools.wraps(func)
  6.     def helper(file, *args, **kwargs):
  7.         return File(file, func, *args, **kwargs)
  8.     return helper
  9.  
  10.  
  11. class File(object):
  12.  
  13.     def __init__(self, file, func, *args, **kwargs):
  14.         self.close_file = kwargs.pop('close', True)
  15.         # accept either filename or file-like object
  16.         self.file = file if hasattr(file, 'read') else open(file)
  17.  
  18.         try:
  19.             # func is responsible for self.file if it doesn't return it
  20.             self.file = func(self.file, *args, **kwargs)
  21.         except:  # clean up on any error
  22.             self.__exit__(*sys.exc_info())
  23.             raise
  24.  
  25.     # context manager support
  26.     def __enter__(self):
  27.         return self
  28.  
  29.     def __exit__(self, *args, **kwargs):
  30.         if not self.close_file:
  31.             return  # do nothing
  32.         # clean up
  33.         exit = getattr(self.file, '__exit__', None)
  34.         if exit is not None:
  35.             return exit(*args, **kwargs)
  36.         else:
  37.             exit = getattr(self.file, 'close', None)
  38.             if exit is not None:
  39.                 exit()
  40.  
  41.     # iterator support
  42.     def __iter__(self):
  43.         return self
  44.  
  45.     def __next__(self):
  46.         return next(self.file)
  47.  
  48.     next = __next__  # Python 2 support
  49.  
  50.     # delegate everything else to file object
  51.     def __getattr__(self, attr):
  52.         return getattr(self.file, attr)
  53.  
  54.  
  55. @file_reader
  56. def f(file):
  57.     print(repr(file.read(10)))
  58.     return file
  59.  
  60. file = f('prog.py')  # use as ordinary function
  61. print(repr(file.read(20)))
  62. file.seek(0)
  63. for line in file:
  64.     print(repr(line))
  65.     break
  66. file.close()  # need to close explicitly
  67.  
  68. with f('prog.py') as file:  # use as a context manager
  69.     print(repr(file.read(20)))
Success #stdin #stdout 0.02s 5824KB
comments (?)
stdin
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Standard input is empty
stdout
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'import fun'
'ctools\nimport sys\n\nd'
'import functools\n'
'import fun'
'ctools\nimport sys\n\nd'
https://ideone.com/RMhe4r
language:
Python 3 (python  3.9.5)
created:
11 years ago
visibility:
secret

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