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Asked: 2026-05-13T05:42:39+00:00

Im working on a data packet retrieval system which will take a packet, and

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Im working on a data packet retrieval system which will take a packet, and process the various parts of the packet, based on a system of tags [similar to HTML tags].
[text based files only, no binary files].

Each part of the packet is contained between two identical tags, and here is a sample packet:

"<PACKET><HEAD><ID><ID><SEQ><SEQ><FILENAME><FILENAME><HEAD><DATA><DATA><PACKET>"

The entire packet is contained within the <PACKET><PACKET> tags.
All meta-data is contained within the <HEAD><HEAD> tags and the filename from which the packet is part of is contained within the, you guessed it, the <FILENAME><FILENAME> tags.

Lets say, for example, a single packet is received and stored in a temporary string variable called sTemp.
How do you efficiently retrieve, for example, only the contents of a single pair of tags, for example the contents of the <FILENAME><FILENAME> tags?

I was hoping for such functionality as saying getTagFILENAME( packetX ), which would return the textual string contents of the <FILENAME><FILENAME> tags of the packet.
Is this possible using Python?

Any suggestions or comments appreciated.

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1 Answer

  1. Editorial Team

    If the packet format effectively uses XML-looking syntax (i.e., if the “closing tags” actually include a slash), the xml.etree.ElementTree could be used.
    This libray is part of Python Standard Library, starting in Py2.5. I find it a very convenient one to deal with this kind of data. It provides many ways to read and to modify this kind of tree structure. Thanks to the generic nature of XML languages and to the XML awareness built-in the ElementTree library, the packet syntax could evolve easily for example to support repeating elements, element attributes.

    Example:

    >>> import xml.etree.ElementTree
>>> myPacket = '<PACKET><HEAD><ID>123</ID><SEQ>1</SEQ><FILENAME>Test99.txt</FILE
NAME></HEAD><DATA>spam and cheese</DATA></PACKET>'
>>> xt = xml.etree.ElementTree.fromstring(myPacket)
>>> wrk_ele = xt.find('HEAD/FILENAME')
>>> wrk_ele.text
'Test99.txt'
>>>
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