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 byLEPTRIS_LIB_PATH(which must name the library file — the loaderdlopens 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/format-time, JSON, map:/array: constructors · format-number works in plain XPath since 1.9.80 |
| 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.
Advisory: libleptris dispatch-index regression (leptris/leptris#875)
Stylesheets with more than ~48 distinct literal template names can
silently drop output from the overflow templates under
leptris 1.9.93.0 and 1.9.94.0 (a fixed-capacity table in
the 1.9.93 predicate index; verified binding-side — 48 of 120
fire, still present in 1.9.94). If you transform large
stylesheets, pin leptris==1.9.90.0 until the fix ships; this
advisory is removed with the fix release.
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
Since libleptris 1.9.76 the output is byte-exact with lxml's
etree.HTMLParser (minimized attributes are empty strings; no
empty <head/> is emitted) — leptris/leptris#813.
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; XSLT raises XSLTError, XQuery XQueryError — all 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 inelement.pyleptris/element.py,document.py,node.py,xpath.py— the Python surface: queries, walks, documents;node.pyexposes the full DOM (comments, CDATA, PIs) beneath the ElementTree shapeleptris/api.py—fromstring/parse/tostring/c14n/iterparseleptris/sax.py— SAX one-shot and streamingtests/— pytest suite (pytestwithLEPTRIS_LIB_PATHset)benchmarks/— matrix vs lxml/ElementTree/minidom (pip install .[bench], thenpython -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. Since 1.9.76.0 the package version is
{c-full-semver}.{patch} — the pinned libleptris version plus
a binding-local patch counter: lib 1.9.76 → 1.9.76.0, then
1.9.76.1 for binding-only fixes against the same pin, resetting
the patch whenever the pin moves. (1.2.0–1.27.1 were the interim
own-semver line.) 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
Release files for leptris 1.9.94.1
For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.
Source distribution (sdist)
| File | Size | Uploaded | |
|---|---|---|---|
| leptris-1.9.94.1.tar.gz | 71.7 kB | Details |
Built distributions (wheels)
| File | Reset | |||
|---|---|---|---|---|
| leptris-1.9.94.1-cp39-abi3-win_amd64.whl | CPython 3.9 | abi3 | Windows x86-64 | Details |
| leptris-1.9.94.1-cp39-abi3-manylinux_2_17_aarch64.manylinux2014_aarch64.whl | CPython 3.9 | abi3 | Linux glibc 2.17+ ARM64 | Details |
| leptris-1.9.94.1-cp39-abi3-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_17_x86_64.manylinux2014_x86_64.whl | CPython 3.9 | abi3 | Linux glibc 2.17+ x86-64, Linux glibc 2.5+ x86-64 | Details |
| leptris-1.9.94.1-cp39-abi3-macosx_11_0_arm64.whl | CPython 3.9 | abi3 | macOS 11.0+ ARM64 | Details |
| leptris-1.9.94.1-cp39-abi3-macosx_10_9_x86_64.whl | CPython 3.9 | abi3 | macOS 10.9+ x86-64 | Details |
Total release size: 428.2 kB
Release files / leptris-1.9.94.1.tar.gz
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