安装M2Crypto遇ModuleNotFoundError: No module named 'swig'错误求助

我已按照M2Crypto安装先决条件文档安装了SWIG，但执行pip3 install M2Crypto时仍抛出错误：ModuleNotFoundError: No module named 'swig'。

环境版本信息 #

• Python版本：3.8
• OpenSSL版本：OpenSSL 1.1.1k
• SWIG版本：4.2.1
• Pip版本：24.0

执行pip3 install --force-reinstall M2Crypto的报错日志 #

pip3 install --force-reinstall M2Crypto
Defaulting to user installation because normal site-packages is not writeable
Looking in indexes: ****
Collecting M2Crypto
  Using cached ****
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'done'
  Installing backend dependencies: started
  Installing backend dependencies: finished with status 'done'
  Preparing metadata (pyproject.toml): started
  Preparing metadata (pyproject.toml): finished with status 'done'
Building wheels for collected packages: M2Crypto
  Building wheel for M2Crypto (pyproject.toml): started
  Building wheel for M2Crypto (pyproject.toml): finished with status 'error'
  error: subprocess-exited-with-error
  
  × Building wheel for M2Crypto (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [59 lines of output]
      INFO:run_command:running bdist_wheel
      INFO:run_command:running build
      INFO:run_command:running build_py
      INFO:copy_file:copying src/M2Crypto/util.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/threading.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/m2xmlrpclib.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/m2urllib2.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/m2urllib.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/m2.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/httpslib.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/ftpslib.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/callback.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/__init__.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/X509.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/SMIME.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/Rand.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/RSA.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/RC4.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/Err.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/Engine.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/EVP.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/EC.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/DSA.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/DH.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/BN.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/BIO.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/AuthCookie.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:copy_file:copying src/M2Crypto/ASN1.py -> build/lib.linux-x86_64-cpython-38/M2Crypto
      INFO:mkpath:creating build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/timeout.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/cb.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/__init__.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/TwistedProtocolWrapper.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/Session.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/SSLServer.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/Context.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/Connection.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/Cipher.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:copy_file:copying src/M2Crypto/SSL/Checker.py -> build/lib.linux-x86_64-cpython-38/M2Crypto/SSL
      INFO:run_command:running egg_info
      INFO:write_pkg_info:writing src/M2Crypto.egg-info/PKG-INFO
      INFO:write_file:writing dependency_links to src/M2Crypto.egg-info/dependency_links.txt
      INFO:write_file:writing requirements to src/M2Crypto.egg-info/requires.txt
      INFO:write_file:writing top-level names to src/M2Crypto.egg-info/top_level.txt
      INFO:read_manifest:reading manifest file 'src/M2Crypto.egg-info/SOURCES.txt'
      INFO:read_template:reading manifest template 'MANIFEST.in'
      WARNING:process_template_line:warning: no files found matching 'src/SWIG/_m2crypto_wrap.c'
      WARNING:process_template_line:warning: no files found matching 'src/M2Crypto/m2crypto.py'
      INFO:add_license_files:adding license file 'LICENCE'
      INFO:execute:writing manifest file 'src/M2Crypto.egg-info/SOURCES.txt'
      INFO:run_command:running build_ext
      INFO:build_extension:building 'M2Crypto._m2crypto' extension
      INFO:swig_sources:swigging src/SWIG/_m2crypto.i to src/SWIG/_m2crypto_wrap.c
      INFO:spawn:swig -python -I/usr/lib/gcc/x86_64-redhat-linux/8/include -I/usr/local/include -I/usr/include -D__x86_64__ -I/usr/local/include/python3.8 -I/usr/include/openssl -includeall -builtin -outdir build/lib.linux-x86_64-cpython-38/M2Crypto -o src/SWIG/_m2crypto_wrap.c src/SWIG/_m2crypto.i
      Traceback (most recent call last):
        File "/home/****/.local/bin/swig", line 5, in <module>
          from swig import swig
      ModuleNotFoundError: No module named 'swig'
      error: command '/home/****/.local/bin/swig' failed with exit code 1
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
  ERROR: Failed building wheel for M2Crypto
Failed to build M2Crypto
ERROR: Could not build wheels for M2Crypto, which is required to install pyproject.toml-based projects

解决方案 #

从报错日志可以看到，调用的是/home/****/.local/bin/swig，这是一个Python脚本而非系统级的SWIG工具，问题出在这里：

1. 卸载冲突的Python swig包
   执行以下命令卸载误装的Python版swig：

   pip uninstall -y swig
   

2. 确认系统级SWIG工具的存在
   执行which swig，如果输出是系统路径（如/usr/bin/swig）则正常；如果没有输出，说明系统未安装SWIG，用对应包管理器安装：

   • Debian/Ubuntu系：sudo apt-get install swig
   • RHEL/CentOS系：sudo yum install swig

3. 重新安装M2Crypto
   执行：

   pip3 install M2Crypto
   

内容的提问来源于stack exchange，提问作者Thomas