[Python-Dev] cpython: Optimize tostringlist by taking the stream class outside the function. It's now

[Georg Brandl]

Uh, optimizations are not exactly what I want to see during feature freeze.

Georg

On 07/17/2012 02:10 PM, eli.bendersky wrote:
> http://hg.python.org/cpython/rev/51978f89e5ed
> changeset:   78156:51978f89e5ed
> user:        Eli Bendersky <eliben at gmail.com>
> date:        Tue Jul 17 15:09:12 2012 +0300
> summary:
>   Optimize tostringlist by taking the stream class outside the function. It's now 2x faster on short calls. Related to #1767933
> 
> files:
>   Lib/xml/etree/ElementTree.py |  38 +++++++++++++----------
>   1 files changed, 22 insertions(+), 16 deletions(-)
> 
> 
> diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
> --- a/Lib/xml/etree/ElementTree.py
> +++ b/Lib/xml/etree/ElementTree.py
> @@ -1184,23 +1184,29 @@
>  # @defreturn sequence
>  # @since 1.3
>  
> +class _ListDataStream(io.BufferedIOBase):
> +    """ An auxiliary stream accumulating into a list reference
> +    """
> +    def __init__(self, lst):
> +        self.lst = lst
> +        
> +    def writable(self):
> +        return True
> +
> +    def seekable(self):
> +        return True
> +
> +    def write(self, b):
> +        self.lst.append(b)
> +
> +    def tell(self):
> +        return len(self.lst)
> +
>  def tostringlist(element, encoding=None, method=None):
> -    data = []
> -    class DataStream(io.BufferedIOBase):
> -        def writable(self):
> -            return True
> -
> -        def seekable(self):
> -            return True
> -
> -        def write(self, b):
> -            data.append(b)
> -
> -        def tell(self):
> -            return len(data)
> -
> -    ElementTree(element).write(DataStream(), encoding, method=method)
> -    return data
> +    lst = []
> +    stream = _ListDataStream(lst)
> +    ElementTree(element).write(stream, encoding, method=method)
> +    return lst
>  
>  ##
>  # Writes an element tree or element structure to sys.stdout.  This
> 
> 
> 
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