Cleanup guarantees?

[Alf P. Steinbach]

* Gabriel Genellina:
> En Fri, 09 Apr 2010 01:13:37 -0300, Alf P. Steinbach <alfps at start.no> 
> escribió:
> 
>  > <code language="Py3">
>  > import urllib.request   # urlopen
>  > import codecs           # getreader
>  > import sys              # stderr
>  >
>  > def text_stream_from( url, encoding ):
>  >      text_reader = codecs.getreader( encoding )
>  >      connection = urllib.request.urlopen( url )
>  >      return text_reader( connection )
>  >
>  > def list_text( url, encoding ):
>  >      lines = text_stream_from( url, encoding )
>  >      for line in lines:
>  >          print( line, end = "" )
>  >      lines.close()       # Undocumented?
>  >
>  > url = "http://www.rfc-editor.org/rfc/rfc1149.txt"
>  > list_text( url, "ascii" )
>  > </code>
>  >
>  > First, I'm unable to find documentation that there /is/ a close 
> method in the
>  > text_reader object, and I'm unable to find documentation that there 
> is a close
>  > method in the file like connection object; is there such documentation?
> 
> codecs.getreader returns a StreamReader instance (see [1])
> StreamReader is documented here [2] and it says "In addition to the 
> above methods, the StreamReader must also inherit all other methods and 
> attributes from the underlying stream." -- the stream being 
> 'connection', from urllib.request.urlopen.
> The 3.x version of the documentation in [3] doesn't provide any details 
> except being "a file-like object". The 2.x version [4] is much more 
> clear: "a file-like object is returned. This supports the following 
> methods: read(), readline(), readlines(), fileno(), close(), info(), 
> getcode() and geturl(). It also has proper support for the iterator 
> protocol."
> 
> [1] http://docs.python.org/py3k/library/codecs.html#codecs.getreader
> [2] http://docs.python.org/py3k/library/codecs.html#codecs.StreamReader
> [3] 
> http://docs.python.org/py3k/library/urllib.request.html#urllib.request.urlopen 
> 
> [4] http://docs.python.org/library/urllib.html#urllib.urlopen

Thanks.


>  > Second, I'm unable to find documentation of when they're called and 
> what they
>  > do. It seems that (A) when the connection object's st
>  method is called automatically, and (B) that when the
>  > text_reader object's close method is called it calls the close method 
> of the
>  > wrapped stream (i.e. on the connection object). But where is this 
> documented?
> 
> Nowhere, AFAIK.
> I bet documentation patches are welcome.

Well, I think I know too little about intentions to do any documentation patches.


Cheers,

- Alf