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xpathlet

A pure Python XPath implementation that operates on ElementTree objects.

The only external dependency is PLY, which is a pure Python lex/yacc implementation. (There is also a alternate parser which uses parsley, but that's currently much slower and is therefore not the default.)

xpathlet is covered by the MIT license. See the LICENSE file for details.

Features

At the moment, xpathlet consists of:

  • A probably-buggy parser that builds a probably-broken AST.

  • A definitely-incomplete expression engine that understands:

    • Basic location paths and node tests.
    • Positional predicate expressions.
    • Comparison and arithmetic operators.
    • Functions calls.

  • A definitely-incomplete core function library.

In the future, it will hopefully be a fully standards-compliant XPath 1.0 implementation that operates on ElementTree objects. Except maybe not around namespaces.

Issues

There are a few things that are somewhat hard to implement completely, so they have "good enough" implementations. These might be fixed later.

  • Namespace handling is a bit weird. This is mostly a consequence of how ElementTree handles namespaces.

  • Element IDs are assumed to be in the id attribute.

Testing

There aren't very many unit tests around the actual implementation (yet), but there is a test harness (conformance.py) to run the subset of the OASIS XSLT test suite v0.4 (not included) that relates to XPath.

The harness includes a half-hearted partial implementation of some of XSLT. This should not be considered an actual XSLT implementation.

Why? WHY!?

I've been asking myself that a lot. I need an XPath implementation that doesn't pull in non-Python dependencies for my XForms implementation that isn't Java. The expected benefits outweigh the pain for now, but that may not last forever.