[Tutor] help on StringIO

[Kent Johnson]

On Mon, May 26, 2008 at 12:53 PM, inhahe <inhahe at gmail.com> wrote:
> I guess that makes sense, but it seems a lot more useful to have a
> function that only reads what's been written since the last time you
> read.  That way reading from a file that's growing would be
> transparent--the same as reading it as if it were already full size.
> It seems with this read function if you were copying a file, because
> the file might be growing you'd have to do this:
> while 1:
>  p = f1.tell()
>  f2.write(f1.read(4096))
>  f1.seek(p+4096)
> otherwise your copy process would quit as soon as any new data is
> written, because the file position would jump to the end of the file.

You are confusing reading and writing a single file using a single
file handle, and reading from one file and writing to another.
>
> and getvalue just returns the entire contents of the buffer.
>>>> s.write('hi')
>>>> s.getvalue()
> 'hi'
>>>> s.write('hi')
>>>> s.getvalue()
> 'hihi'
>
> so i'd be getting redundant data.
>
> What i'm wondering about specifically is WSGI.  it's supposed to
> return a file-like object, wsgi.input, for reading the http request.
> and if you read beyond what's currently received, it's supposed to
> block until more is received.  so are we actually supposed to read
> from wsgi.input by doing this?
>
> while 1:
>  p = wsgi.input.tell()
>  processe(wsgi.input.read(4096))
>  wsgi.input.seek(p+4096)  # otherwise the next time something is
> added to wsgi.input your reading will return nothing

No, just read from the input.

> and even then i suppose the WSGI server had better not write anything
> to the stream before it's all read up otherwise it'll overwrite to
> some position in the middle of the stream (wherever the current
> position is).  this makes no sense to me.  how is this done? (and
> where's the file class that works in a way that makes sense?)

Can you show an example of why you need this?

Kent

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