ImportError: cannot import name packaging from pkg_resources in Causal-Conv1d
Upgrade setuptools (pip install --upgrade setuptools wheel packaging) and install with --no-build-isolation to share the active host environment.
Root Cause Analysis
This error occurs when Python tries to build a custom CUDA/C++ extension (such as causal_conv1d, flash-attn, or mamba-ssm) from source, and the extension's setup.py attempts to import packaging from pkg_resources (from pkg_resources import packaging), which was removed in modern setuptools releases (setuptools >= 70.0.0).
1. Deprecation and Removal of Vendored packaging in pkg_resources
Historically, setuptools.pkg_resources vendored an internal copy of the packaging module. In modern versions of setuptools, vendored sub-modules were removed, and developers must import directly from the standalone packaging package (import packaging.version).
2. Hardcoded Legacy Imports in CUDA Extension Repositories
Many deep learning acceleration repositories authored between 2021 and 2023 hardcoded from pkg_resources import packaging inside their setup.py to compare PyTorch and CUDA versions.
3. Pip Build Isolation Creating Fresh Incompatible Environments
By default, pip install creates an isolated ephemeral build environment with the latest version of setuptools, triggering the import failure.
4. Standalone packaging Package Availability
The standalone packaging library is available in all modern Python environments and provides direct access to packaging.version.parse.
Reproduction Code (MCVE)
# **Note de reproductibilité :** Lié à l'environnement de build Python.
raise ImportError("cannot import name 'packaging' from 'pkg_resources' (/usr/local/lib/python3.12/site-packages/pkg_resources/__init__.py)")
Solution 1: Install with --no-build-isolation Flag
Pre-install build requirements in your active environment and disable pip build isolation during installation.
import sys
print('Execute in terminal to install CUDA extension with pinned build tools:')
print('pip install setuptools==69.5.1 wheel packaging ninja torch')
print('pip install causal-conv1d --no-build-isolation')
Solution 2: Patch setup.py to Import Standalone packaging
If building from a cloned repository, replace from pkg_resources import packaging with import packaging.version.
import packaging.version
v1 = packaging.version.parse('2.1.0')
v2 = packaging.version.parse('2.2.0')
print(f'Version comparison working correctly: {v1 < v2}')
A common mistake is repeatedly running pip install causal-conv1d without --no-build-isolation. Because pip creates a temporary isolated build virtualenv with the latest setuptools on every run, the fix will not take effect without the flag. Edge cases occur in Docker builds: set ENV PIP_NO_BUILD_ISOLATION=1 in your Dockerfile. Contrast this error with ImportError: cannot import name 'version' from 'packaging', which indicates an outdated standalone packaging package.