pycomtypelib

A pure-Python, cross-platform decoder for the MSFT COM type library binary format (.tlb files, and RT_TYPELIB resources embedded in .dll / .ocx / .exe files). No Windows, no COM, no oleaut32.dll required.

This is a Python port of the type library reading logic in Wine's dlls/oleaut32/typelib.c and typelib.h, cross-checked against public documentation of the format (notably Geoff Chappell's notes on ITypeLib). Only the MSFT format is supported (the format produced by ICreateTypeLib2 / MIDL and used by essentially all modern type libraries); the older SLTG format (ICreateTypeLib, legacy VB5/VB6) is out of scope.

Wine's typelib.c is licensed LGPL-2.1-or-later; this project inherits that license since its parsing logic is derived from it.

Install

pip install -e .

Library usage

from pycomtypelib import load_typelib_file

tlb = load_typelib_file("stdole2.tlb")
print(tlb.name, tlb.guid, tlb.version)
for ti in tlb.typeinfos:
    print(ti.typekind.name, ti.name)

To pull a type library out of a compiled binary (DLL/OCX/EXE) instead of a standalone .tlb file:

from pycomtypelib import load_typelib_from_pe

tlb = load_typelib_from_pe("MSCOMCTL.OCX")

CLI

pycomtypelib dump stdole2.tlb
pycomtypelib dump MSCOMCTL.OCX --json > mscomctl.json

Cross-library references (e.g. an interface inheriting from IUnknown or IDispatch, which live in stdole2.tlb) can't be resolved to a full TypeInfo without also parsing the imported library, so by default they're shown by name via a small built-in table of well-known COM/OLE Automation interface GUIDs (pycomtypelib.WELL_KNOWN_INTERFACES). Pass -n / --no-wellknown-guids to disable that and show the raw GUID and import library name instead:

pycomtypelib dump -n stdole2.tlb

This only affects display (--json's wellknown_name field, and the IDL-like text renderer); it never affects decoding itself.

Scope

• Reads the MSFT binary layout: header, segment directory, GUID/name/string tables, type descriptors, array descriptors, per-TypeInfo function/variable/ implemented-type records, imported type libraries, and custom data.
• Resolves this into a friendly object model (TypeLib, TypeInfo, FuncDesc, VarDesc, ParamDesc, TypeDesc, ...) analogous to what ITypeInfo exposes, including resolution of VT_USERDEFINED references to other TypeInfo entries (in the same library or in imported libraries).
• Read-only: this library decodes type libraries, it does not write/compile them.