cppyy-cling

6.32.8 verified Fri May 01 auth: no python

Re-packaged Cling C++ interpreter, used as the JIT backend for cppyy. Provides the C++ runtime and interpreter for cppyy's automatic Python-C++ bindings. Version 6.32.8, released on 2025-05-26. Release cadence follows cppyy releases.

pip install cppyy-cling

Common errors

error ModuleNotFoundError: No module named 'cppyy_backend' ↓

cause Attempting to import cppyy_backend instead of cppyy, or missing cppyy-cling installation.

fix

Install cppyy-cling: pip install cppyy-cling. Then use 'import cppyy'.

error RuntimeError: cppyy backend not found. Please install cppyy-cling or set CPYY_BACKEND ↓

cause cppyy-cling not installed or not found by cppyy.

fix

Run: pip install cppyy-cling. Ensure it's installed in the same Python environment.

error ImportError: cannot import name 'gbl' from 'cppyy' ↓

cause Using 'from cppyy import gbl' incorrectly; correct is 'from cppyy import gbl' (if you write import cppyy.gbl it's wrong). But if you do from cppyy import gbl it works.

fix

Use either 'from cppyy import gbl' or 'import cppyy; gbl = cppyy.gbl'.

Warnings

gotcha cppyy-cling is a separate package from cppyy. You must install cppyy-cling explicitly (or let cppyy install it as a dependency). If only cppyy is installed, the backend may be missing. ↓

fix pip install cppyy-cling

gotcha Do not import cppyy_backend or cppyy_cling directly. The correct way to use the backend is through cppyy. cppyy auto-detects cppyy-cling. ↓

fix Use 'import cppyy' and then use cppyy functions.

breaking In cppyy-cling 6.32.x, the default C++ standard may be C++17. Code relying on C++11 or C++14 features might behave differently. Explicitly set standard with cppyy.add_include_path or cling flags. ↓

fix Use cppyy.cppdef('...') or pass -std=c++14 to cppyy.add_include_path via cppyy.load_library.

Imports

cppyy
wrong
```
import cppyy_backend
```
correct
```
import cppyy
```
cppyy-cling is not imported directly; it's a backend for cppyy
cppyy.gbl
wrong
```
import cppyy.gbl
```
correct
```
from cppyy import gbl
```
cppyy.gbl is a module, not a subpackage; use from cppyy import gbl

Quickstart

Basic usage: import cppyy (which loads cppyy-cling backend), include a C++ header, and call C++ functions.

import cppyy
cppyy.include('iostream')
cppyy.gbl.std.cout << 'Hello from C++ via cppyy' << cppyy.gbl.std.endl