Py3K: file inheritance

[Yosifov Pavel]

In the Python 2.x was simple to create own file object:

class MyFile(file):
pass

for example to reimplement write() or something else. How to do it in
Python 3.x?

 

[Ian Kelly]

In the Python 2.x was simple to create own file object:

class MyFile(file):
špass

for example to reimplement write() or something else. How to do it in
Python 3.x?

See the docs for the io module. Depending on what you want to do, you
probably need to subclass either io.FileIO or io.TextIOWrapper.

 

[Yosifov Pavel]

See the docs for the io module.  Depending on what you want to do, you
probably need to subclass either io.FileIO or io.TextIOWrapper.

Little silly example:

class MyFile(file):
def __init__(self, *a, **ka):
super(MyFile, self).__init__(*a, **ka)
self.commented = 0
def write(self, s):
if s.startswith("#"):
self.commented += 1
super(MyFile, self).write(s)

When I tried in Python 3.x to inherit FileIO or TextIOWrapper and then
to use MyFile (ex., open(name, mode, encoding), write(s)...) I get
errors like 'unsupported write' or AttributeError 'readable'... Can
you show me similar simple example like above but in Python 3.x?

 

[Ian Kelly]

Little silly example:

class MyFile(file):
šdef __init__(self, *a, **ka):
š šsuper(MyFile, self).__init__(*a, **ka)
š šself.commented = 0
šdef write(self, s):
š šif s.startswith("#"):
š š šself.commented += 1
š š šsuper(MyFile, self).write(s)

When I tried in Python 3.x to inherit FileIO or TextIOWrapper and then
to use MyFile (ex., open(name, mode, encoding), write(s)...) I get
errors like 'unsupported write' or AttributeError 'readable'... Can
you show me similar simple example like above but in Python 3.x?

class MyTextIO(io.TextIOWrapper):
def __init__(self, *args, **kw):
super().__init__(*args, **kw)
self.commented = 0
def write(self, s):
if s.startswith('#'):
self.commented += 1
super().write(s)

buffered = open(name, 'wb')
textio = MyTextIO(buffered, encoding='utf-8')
textio.write('line 1')
textio.write('# line 2')
textio.close()
print(textio.commented)

HTH,
Ian