pyrfcx

pyrfcx is an SAP NW RFC client for Python with a Rust core. It installs the import package pyrfc, a drop-in replacement for the client part of SAP's pyrfc 3.4, which SAP has archived. The pyrfc package reproduces the quirks of pyrfc 3.4, each one measured on real pyrfc first.

How it ships:

• Install with pip, no compiler. pyrfc 3.4 is not on PyPI. It needs a build from source for each CPython version.
• New CPython versions run without a new release. One abi3 wheel runs on CPython 3.10 and later. Tested from 3.10 to 3.15.
• New SDK patch levels run without a change. pyrfcx loads the SDK at run time. Tested from 7.50 patch level 11 to 20.

Limits: client only, standard (GIL) CPython only. A call releases the GIL during network operations.

Install

pip install pyrfcx

Remove real pyrfc from the environment first: both install the import name pyrfc.

Use

from pyrfc import Connection

with Connection(dest="MY_DEST") as conn:
    result = conn.call("STFC_CONNECTION", REQUTEXT="hi")
    print(result["ECHOTEXT"])

dest names a destination in a sapnwrfc.ini file. By default the SDK reads that file from the current directory. You can also pass the connection parameters directly (ashost, sysnr, client, user, passwd, and so on).

What is supported

Area	Members
Connection	Connection(config=..., **params), open(), close(), reopen(), is_valid(), alive, context manager
Calls	call(name, options=..., **params), ping(), cancel()
config keys	rstrip, return_import_params, dtime, check_date, check_time, timeout
call options	not_requested, timeout
Information	version, options, get_connection_attributes()
Descriptions	get_function_description(), with FunctionDescription, TypeDescription, RfcFieldType and RfcParameterDirection
Module functions	get_nwrfclib_version(), cancel_connection(), set_ini_file_directory(), reload_ini_file(), set_cryptolib_path()
Exceptions	The pyrfc classes, with the same names and the same attributes: RFCError, RFCLibError, CommunicationError, LogonError, ABAPApplicationError, ABAPRuntimeError, ExternalAuthorizationError, ExternalApplicationError, ExternalRuntimeError, RFCTypeError

What is not supported

• Server, Throughput, tRFC, qRFC, bgRFC and WebSocket RFC. This is a client library, so these are out of scope.
• Not built yet: free(), reset_server_context(), type_desc_get(), type_desc_remove(), func_desc_remove(), set_locale_radix(), the language converters and ConnectionParameters.
• Connection.handle is not exposed. The Rust core owns the SDK handle.

Tests

Every live test runs against a real ABAP system. The compat suite runs twice on the same SDK: once on pyrfc from pyrfcx and once on real pyrfc 3.4. Both runs must give the same results.

Suite	pyrfc 3.4	pyrfc (pyrfcx)	pyrfcx	C SDK
pyrfc 3.4's own tests, adapted (tests/compat/)	78	78	–	–
Added compat tests, each expectation measured on real pyrfc first	56	56	–	–
Behaviour facts (unpublished)	168	168	168	168

Performance against real pyrfc

Time was measured on macOS arm64 with SDK 7.50 patch level 15; memory on Windows x64 with patch level 18.

Time. On large tables pyrfc from pyrfcx is faster than pyrfc 3.4 and uses less CPU. On small calls the two are the same: the backend sets the pace. Seconds per call, median of 10 runs in fresh processes:

Case	Measure	pyrfc 3.4	pyrfc (pyrfcx)	pyrfc (pyrfcx) is
RFC_READ_TABLE, 100 000 rows of DD03L	Wall time CPU time	5.79 1.13	5.62 0.99	3 % better 13 % better
100 000 rows of 40 × CHAR(15)	Wall time CPU time	10.98 6.30	9.97 5.27	9 % better 16 % better

Memory. pyrfc from pyrfcx never uses more memory than pyrfc, and its results are smaller: all row dicts share one string object per key. Bytes per table row:

Table shape	Measure	pyrfc 3.4	pyrfc (pyrfcx)	pyrfc (pyrfcx) is
40 × CHAR(15)	Peak memory Size of the result	5 508 5 429	3 606 3 468	35 % better 36 % better
1 × CHAR(512)	Peak memory Size of the result	1 201 614	1 199 561	same 9 % better
Audit log, 30 fields incl. STRING	Peak memory Size of the result	4 993 4 007	4 989 2 333	same 42 % better

Status

• Version 0.1. The pyrfc API is complete for the client members listed below, and stable.
• Platforms. Wheels exist for Windows x64, macOS arm64 (macosx_11_0_arm64), and Linux x86_64 and aarch64 (manylinux_2_28). All are cp310-abi3.
• Client only. Server RFC, tRFC, qRFC and bgRFC are not supported.
• The native pyrfcx package is not a supported API yet. It ships in the same install because pyrfc runs on it. Its interface may change in any 0.x release and it is not documented here. See "The engine" below.

Requirements

1. The SAP NW RFC SDK 7.50, patch level 11 or later, for your platform. Patch levels from 5 should also work, but they are untested. The SDK changed its behaviour between patch levels in a few places: docs/sdk-patch-levels.md. The SDK belongs to SAP and is not part of this distribution. Download it from the SAP Support Portal (support.sap.com). You need an S-user.
2. The environment variable SAPNWRFC_HOME. Set it to the SDK directory (the directory that contains lib/).
3. CPython 3.10 or later, built for the same architecture as the SDK.
   • Windows: SAP ships the SDK for x64 only. Use an x64 Python, even on an ARM64 machine. An ARM64 Python cannot load the x64 SDK.
   • Linux: the wheel needs glibc 2.28, but the SDK needs more: GLIBCXX_3.4.26 (the libstdc++ of GCC 9) and libuuid.so.1. The wheel runs only where the SDK runs.

With SAPNWRFC_HOME set, nothing else is needed: no PATH or LD_LIBRARY_PATH entry, on any platform. Without it, the SDK is searched by name, and on Windows a stray copy of sapnwrfc.dll can be found whose ICU libraries are not: the first connect then hangs on a hidden "could not open ICU library" dialog instead of failing. Set SAPNWRFC_HOME.

pyrfc 3.4 quirks that the drop-in keeps

A program can depend on a quirk, so pyrfc from pyrfcx reproduces the quirks below.

Case	pyrfc 3.4 and the drop-in
A CHAR value ends with a tab or a newline that belongs to the data	The character is removed. "AB\t" comes back as "AB".
A STRING value ends with blanks	The blanks are removed. "AB " comes back as "AB".
A DATE field is initial	Comes back as "". You cannot tell it from an empty value.
A CHAR input is longer than the field	The SDK truncates the value. No error.
256 for an INT1 field, 32768 for an INT2 field	The value wraps. No error. For INT1 the backend gets 0.
An IntEnum value for an integer field	Raises TypeError.
An output parameter is deactivated with not_requested	The result contains the parameter with an initial value that the backend never sent.
A scalar parameter is in not_requested and also has a value	The value is sent.
str() of an exception	The text should start with the name of the return code, such as RFC_INVALID_HANDLE (rc=5): .... It shows the number twice instead: 5 (rc=5): ....
cancel() fails, for example because no call is running	cancel() runs the SDK call in a new thread and returns at once. The error is raised in that thread and printed to stderr; the caller cannot catch it.
get_connection_attributes()["dest"]	The value is always empty.

Each row is measured on real pyrfc 3.4.

Moving from pyrfc 3.3.1

The drop-in follows pyrfc 3.4, not pyrfc 3.3.1. One difference is visible: the message of a CommunicationError has no trailing newline. pyrfc 3.3.1 keeps the newline that the SDK sends. pyrfc 3.4 right-strips the message, and the drop-in does the same. Code that stores the message stores one character less.

The engine

pyrfcx shares no code with pyrfc. pyrfcx is a new binding of the SAP NW RFC SDK, written in Rust. The pyrfc package is a thin Python layer on top of it that reproduces the pyrfc 3.4 API.

You need no Rust and no compiler to use it. Pre-compiled wheels exist for Windows x64, macOS arm64 and Linux x86_64 and aarch64, for CPython 3.10 and later.

The Rust core loads the SDK at runtime and marshals the character, number, date and time, byte, structure and table types without loss. A call holds the GIL only to build the Python result. The core never closes a handle that the SDK has already freed. The pyrfc package is a facade over the core that reproduces pyrfc's conversions and its quirks.

The native pyrfcx Python API is installed with the facade, but it is not a supported interface yet. It may change in any 0.x release. Use import pyrfc. The native API gets its own documentation when it is ready.

Build from source

You need Rust (stable, 1.95 or later), CPython 3.10 or later and uv. On Windows the Python must be x64. The build does not need the SDK: the package loads it at runtime.

git clone https://github.com/bougebouge/pyrfcx
cd pyrfcx
uv venv --python <path-to-python>
uv pip install "maturin>=1.5,<2"    # or `just sync`, which installs every dev tool

# Build the wheel into target/wheels (on Windows add --target x86_64-pc-windows-msvc)
uv run maturin build --release --out target/wheels

# Install it
uv pip install --find-links target/wheels pyrfcx

just wheels builds the same pyrfcx wheel with the source paths remapped, so the binary holds no path of the build machine; prefer it for a wheel you give to others.

For a development install, use an editable build:

uv run maturin develop --uv     # on Windows add --target x86_64-pc-windows-msvc

The Linux wheels are built in Docker (just linux-wheel <arch>). The tests need a live ABAP system. See CONTRIBUTING.md.

More

• Development: CONTRIBUTING.md

License

pyrfcx is licensed under the Apache License, Version 2.0. The SAP NW RFC SDK is not covered by this license. See NOTICE.

SAP, SAP NetWeaver and the SAP NW RFC SDK are trademarks or registered trademarks of SAP SE in Germany and other countries. pyrfc is SAP's Python RFC connector. This project is not affiliated with, endorsed by or sponsored by SAP SE.