python 3.x - How to use a generator inside an openhook in a fileinput object? -

i try replace tabulation characters 8 whitespaces in fileinput structure using openhook argument of fileinput class.

here current source code:

from io import textiowrapper  class iterstream(textiowrapper):     """     file-like streaming iterator.     """     def __init__(self, generator):         self.generator = generator         self.iterator = iter(generator)         self.leftover = ''      def __iter__(self):         return self.iterator      def next(self):         return self.iterator.next()      def __next__(self):         return self.iterator.__next__()      def read(self, size):         data = self.leftover         count = len(self.leftover)         try:             while count < size:                 chunk = self.__next__()                 data += chunk                 count += len(chunk)         except stopiteration:             self.leftover = ''             return data          return data[:size]      def readline(self, size):         return self.read(size)      def readlines(self, size):         return self.read(size)      def close(self):         pass  def streamfilter(filter):     def stream(iostream):         return iterstream(filter(iostream))     return stream  @streamfilter def tab_filter(stream):     line in stream:         yield line.replace ('\t', ' ' * 8)   def fileinput_hook(filename, mode):     return tab_filter(open(filename, mode))          if __name__ == "__main__":     import fileinput      f = fileinput.input(files='file.txt', openhook=fileinput_hook)      line in f:         print(f.filename() + ": " + str(f.filelineno()) + ": " + line) 

note follow reasonning (i might wrong way do):

1. i try create generator (tab_filter) able transform tabulation 8 whitespaces.

2. then, create wrapper can take generator/iterator , pretend normal file (iterstream).

3. i add few cosmetic changes make easier manipulate filters (the @streamfilter decorator).

4. i create fileinput_hook() function intended hook on file inside fileinput object.

once done, have create fileinput object , browse through it.

unfornately, following error:

traceback (most recent call last):   file "./example.py", line 60, in <module>     line in f:   file "/usr/lib/python3.5/fileinput.py", line 265, in __next__     line = self.readline()   file "/usr/lib/python3.5/fileinput.py", line 370, in readline     self._buffer = self._file.readlines(self._bufsize)   file "./example.py", line 36, in readlines     return self.read(size)   file "./example.py", line 23, in read     chunk = self.iterator.next() attributeerror: 'generator' object has no attribute 'next' 

so, did wrong, , how achieve want? far? there better ways it?

edit after solving confusion between __next__ , next, following error:

traceback (most recent call last):   file "./example.py", line 63, in <module>     line in f:   file "/usr/lib/python3.5/fileinput.py", line 265, in __next__     line = self.readline()   file "/usr/lib/python3.5/fileinput.py", line 370, in readline     self._buffer = self._file.readlines(self._bufsize)   file "./example.py", line 39, in readlines     return self.read(size)   file "./example.py", line 26, in read     chunk = self.__next__() valueerror: i/o operation on uninitialized object 

edit2

in fact, works alokthakur said... not know happened.

if using python 3.x should use __next__() instead of next()

change

self.iterator.next() 

to

self.iterator.__next__()