leptris (Python) — lxml-shaped bindings for libleptris

leptris wraps the libleptris C API (XML 1.0 parsing, XPath 1.0) using cffi in ABI mode, with a required C accelerator for Element allocation and the hot accessors (tag, text, attrib, get, indexing, sibling navigation and plain-path XPath evaluation). Wheels ship it compiled; sdist builds require a C compiler.

The pinned libleptris version lives in libleptris-version.txt (lockstep releases); CI builds it from the release tarball. The binding loads the shared library from LEPTRIS_LIB_PATH or the loader path.

Requirements

  • Python 3.9+
  • cffi (installed automatically)
  • libleptris 1.9.3+ as a shared library (1.9.1 has an options-struct ABI break — leptris/leptris#568)
  • libleptris as a shared library (libleptris.dylib / .so / .dll) on the loader path, or pointed to by LEPTRIS_LIB_PATH (which must name the library file — the loader dlopens it verbatim). For a development checkout:
cmake -B build -S /path/to/leptris -DLEPTRIS_BUILD_SHARED=ON
cmake --build build --target leptris_shared
export LEPTRIS_LIB_PATH=/path/to/leptris/build/src/libleptris.dylib

Quick start

from leptris import fromstring, tostring

root = fromstring("<library><book id='1' lang='en'>Ulysses</book></library>")

root.tag                                # "library"
root[0].get("id")                       # "1"
root[0].attrib                          # {"id": "1", "lang": "en"}
root[0].text                            # "Ulysses"

root.xpath("count(//book)")             # 1.0
[b.text for b in root.findall("book")]  # ["Ulysses"]

tostring(root[0], encoding="unicode")   # "<book id=\"1\" lang=\"en\">Ulysses</book>"

Documents own the tree; use the context manager or close():

from leptris import parse

with parse("catalog.xml") as doc:
    doc.xpath("//book[@lang='en']")

Namespaces, variables, canonical XML and streaming:

root.xpath("//x:item", namespaces={"x": "urn:ex"})
root.xpath("//book[@id=$id]", variables={"id": "2"})
c14n(root, exclusive=True)

from leptris import sax
sax.parse(xml, handler)                       # one-shot
with sax.StreamingParser(handler) as parser:  # push, constant memory
    parser.feed(chunk, final=last)

XSLT and XPath version support

leptris.XSLT(stylesheet) compiles once, applies to any Document, and returns a Document; leptris.XPath(expression) compiles an XPath for repeated evaluation. Which language constructs work is decided by the engine — the matrix below is measured against libleptris 1.9.32 (audited through this binding; the upstream gap ledger is leptris/leptris#685).

language status notes
XSLT 1.0 full libxslt conformance suite 205/205 upstream; EXSLT math/set/str/date included
XSLT 2.0 partial ✓ for-each-group, analyze-string + regex-group(), xsl:number formats, xsl:assert, xsl:sequence (multi-item), xsl:perform-sort · ✗ xsl:function, tunnel parameters, shadow attributes, xsl:result-document, @separator
XSLT 3.0 increments ✓ try/catch (with $err:description), accumulator (gated by xsl:mode use-accumulators), iterate + break + on-completion, on-empty, evaluate, grouping, modes, where-populated, on-non-empty, next-match, fork, @start-at, composite keys, tunnel params, copy/@select, xsl:namespace, xsl:document, @default, merge, result-document (writes the href target), character maps · ✗ package, xsl:map, xsl:evaluate with-params, next-iteration chaining
XPath 1.0 full complete core function library
XPath 2.0 grammar complete ✓ quantified (some/every), set algebra (union/intersect/except), node comparisons (is, <<, >>), (), ends-with, deep-equal, value comparisons, cast/castable/treat/instance of, function items + HOFs (1.9.73+) · function slices by group (sequences, regex, math:, strings/QNames/URIs, dates, xs: constructors); remaining: format-date, duration arithmetic, JSON, map:/array:
XPath 3.1 lane 0 ✓ let, simple map !, arrow =>, string concat || — through both XPath() and XSLT · ✗ function items, inline functions, maps, arrays, string constructors
XQuery 1.0 core + 3.x increments leptris.XQuery(query) — FLWOR (for/let/where/order by/return/group by, positional at, tumbling/sliding windows), prolog (declare variable/namespace/function local:*), constructors, doc()/collection(), try/catch, typeswitch — libleptris 1.9.68+; 3.1 remainder (maps/arrays, modules) tracked in #684

XQuery 1.0 core is a first-class API since libleptris 1.9.64:

from leptris import Document, XQuery

with Document.parse("<r><item v='1'>alpha</item><item v='5'>beta</item></r>") as doc:
    XQuery("for $i in //item where $i/@v > 1 return string($i)")(doc)  # ['beta']
    XQuery("declare variable $n := 3; <out>{$n * 2}</out>")(doc)       # '<out>6</out>'
    XQuery("declare function local:dbl($x) { $x * 2 }; local:dbl(4)")(doc)  # 8.0

XPath 3.1 composition and XSLT 3.0 instructions flow through the existing API with zero binding change:

from leptris import Document, XPath, XSLT, tostring

with Document.parse("<r><item v='1'>alpha</item><item v='5'>beta</item></r>") as doc:
    doc.getroot().xpath("let $n := //item[2] return $n/@v")      # ['5']
    doc.getroot().xpath("(//item ! string(.)) => count()")        # 2.0

    style = XSLT("""<xsl:stylesheet version="3.0"
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
      <xsl:mode use-accumulators="depth"/>
      <xsl:accumulator name="depth" initial-value="0">
        <xsl:accumulator-rule match="*" phase="start" select="$value + 1"/>
        <xsl:accumulator-rule match="*" phase="end" select="$value - 1"/>
      </xsl:accumulator>
      <xsl:template match="/"><o>
        <xsl:iterate select="//item">
          <i d="{accumulator-before('depth')}"/>
        </xsl:iterate>
      </o></xsl:template>
    </xsl:stylesheet>""")
    print(tostring(style(doc), encoding="unicode"))
    # <o><i d="2"/><i d="2"/></o>   # items sit at depth 2 (r → item)

Unsupported constructs fail at XSLT() compile time or at evaluation with LeptrisError — except two instructions that still produce empty output instead of an error (xsl:map/xsl:map-entry, and xsl:value-of/@separator is ignored); tracked in the #685/#690 ledgers above.

HTML parsing

leptris.html (libleptris 1.9.75+) — tolerant HTML in the shape of lxml's etree.HTMLParser: implied end tags, void elements, case-insensitive names, unquoted attributes, the named-entity table, and a synthesized <html>/<head>/<body> wrapper:

from leptris import html

r = html.fromstring("<p>hello <b>world")   # <html><head/><body><p>hello <b>world</b></p></body></html>
with html.document("<td>c") as doc:
    doc.xpath("count(//td)")               # 1.0

Known divergences from libxml2 (tracked in leptris/leptris#813): minimized attributes take their own name as value (<div a> → a="a"), and an empty <head/> is emitted.

Migrating from lxml

lxml leptris Notes
etree.fromstring / etree.XML fromstring / XML
etree.parse parse paths and file-likes; no URLs
etree.tostring(elem, …) tostring(elem, …) bytes by default, encoding="unicode" for str
elem.tag / .text / .tail same tag uses {uri}local Clark notation; CDATA merges into text (lxml's default parser behavior)
elem.attrib / .get() / .keys() / .items() same attrib is a read-only Mapping
elem.getparent/getnext/getprevious same
elem[i], len(elem), iteration, slices same indexing is child indexing, never attribute lookup
elem.iter() / .iterdescendants() / .itertext() same elements only (ElementTree semantics); lxml's iter() also yields comments/PIs
elem.find/findall/findtext same accepts full XPath 1.0 — a superset of ElementPath — including {uri}local names
elem.xpath(expr, namespaces=…) same plus variables={…} (leptris extension)
etree.c14n / etree.XInclude c14n(…) / doc.process_xinclude()
etree.XMLSyntaxError ParseError XPath failures raise XPathError; both subclass LeptrisError
etree.Element, SubElement, append, set, remove not exposed libleptris has partial mutation upstream (node content setters, set_root, remove_children) — not surfaced here; build trees elsewhere
document-level comments / PIs doc.toplevel_comments() / doc.toplevel_pis() prolog then epilog; requires libleptris 1.9.3+
etree.iterparse leptris.iterparse(source, full_document=False) bounded by the largest subtree; yields ("end", element); elements borrowed until the next yield; tags resolve namespaces (Clark notation, libleptris 1.9.4+). Truncated or malformed input raises ParseError (both modes, libleptris 1.9.15+). full_document=True yields every element in completion order
smart strings plain str XPath string/attribute results
elem.nsmap absent use elem.namespace / elem.prefix and xpath(namespaces=…)
etree.XPath compiled objects leptris.XPath(expression) compile once, evaluate many; contexts, namespaces, and variables supported
etree.XSLT leptris.XSLT(stylesheet) compile once, apply to any Document — see the version support matrix above
parser options (resolve_entities, …) absent libleptris 1.2.0 has no per-parse options
elem.sourceline same requires libleptris 1.3.0+
undeclared XPath prefix raises in lxml evaluates to an empty nodeset here
ATTLIST default attributes applied by lxml's default parser excluded by default (ElementTree-like; XML 1.0 §5 permits either) — Document.parse(xml, attribute_defaults=True) opts in
declared non-UTF-8 bytes (UTF-16, latin-1, …) auto-detected auto-detected — declared encodings route through the converter, others retry on failure (libleptris 1.9.15+)
parser options (remove_blank_text, …) etree.XMLParser(remove_blank_text=True) Document.parse(xml, remove_blank_text=True) — ~35% faster on pretty-printed input; also attribute_defaults=True, recover=True

Layout

  • leptris/_ffi.py — cdef mirror of the public headers + loader (the only place libleptris is declared)
  • leptris/_leptrisaccel.c — the C accelerator (abi3): allocates Elements and runs the hot accessors, subtree iteration, the parse and serialization seams, and the per-document element registry; bound to libleptris by the positional protocol in element.py
  • leptris/element.py, document.py, node.py, xpath.py — the Python surface: queries, walks, documents; node.py exposes the full DOM (comments, CDATA, PIs) beneath the ElementTree shape
  • leptris/api.py — fromstring/parse/tostring/c14n/ iterparse
  • leptris/sax.py — SAX one-shot and streaming
  • tests/ — pytest suite (pytest with LEPTRIS_LIB_PATH set)
  • benchmarks/ — matrix vs lxml/ElementTree/minidom (pip install .[bench], then python -m benchmarks.matrix)

Memory model

The Document owns the whole tree and its pool. Accessor strings are copied into Python str at the boundary, so nothing depends on document lifetime after a call returns. Elements keep a reference to their Document, so the pool cannot be freed while any wrapper is alive. Prefer explicit close() / the context manager; __del__ is a refcounting safety net, not a contract. Using an element after its document is closed raises LeptrisError.

Versioning

libleptris-version.txt pins the library release the binding is built and tested against. From 1.3.0 the package follows its own semver: 1.2.0 shipped an interim bespoke API to no adopters, and 1.3.0 replaces it with the lxml-shaped API (breaking, but pre-adoption). pyproject.toml and leptris/__init__.py must agree at release time.

Publishing

Releases publish to PyPI via .github/workflows/release.yml, using PyPI trusted publishing (no stored credentials). The workflow runs on manual dispatch (ships the version in pyproject.toml) and is called by the libleptris release flow (publish: true), so every libleptris release ships the wheel.

Local development

python3 -m venv .venv
./.venv/bin/pip install --upgrade build pytest cffi
./.venv/bin/pip install -e .[test,bench]
LEPTRIS_LIB_PATH=/path/to/libleptris.dylib ./.venv/bin/python -m pytest tests/ -q

Project links

Data verified by PyPI on Sep 3, 2026
Data provided by the project maintainers, verified at the time the release was uploaded to PyPI.

Key dates

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  • Released:
Newer release available (1.27.1)

1 maintainer

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Avatar for leptris from gravatar.com leptris

Credits

Author: Ribose

GitHub Statistics

Data verified by PyPI on Sep 3, 2026
The GitHub source repository was provided by the project maintainers and verified by PyPI at the time of upload. Stars, forks, and open issues/PRs are derived from that repository and have not been independently verified.

License expression

MIT
View SPDX License List

Requires

Python >=3.9

Provides Extra

test bench

Tags

xml xpath parser lxml ffi cffi

Classifiers

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