ffi 库无法从 cryptography.hazmat.bindings._openssl 加载

Question

我正在尝试使用 anaconda（python 3.7 64 位）和 pymysql 包在 Windows 10 上打开 mysql 数据库。

在 Windows 命令提示符下，我执行以下操作：

import pymysql
db = pymysql.connect(host='localhost', user='tester', passwd='xxxx', port=3306, db='mydb')

用户名、密码、端口正确；主机应该是 localhost（如果我传递 127.0.0.1，我会得到同样的错误）；但我收到以下错误，最后指出它找不到 ffi 包：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\programs\Anaconda3\lib\site-packages\pymysql\__init__.py", line 94, in Connect
    return Connection(*args, **kwargs)
  File "C:\programs\Anaconda3\lib\site-packages\pymysql\connections.py", line 327, in __init__
    self.connect()
  File "C:\programs\Anaconda3\lib\site-packages\pymysql\connections.py", line 598, in connect
    self._request_authentication()
  File "C:\programs\Anaconda3\lib\site-packages\pymysql\connections.py", line 873, in _request_authentication
    auth_packet = _auth.caching_sha2_password_auth(self, auth_packet)
  File "C:\programs\Anaconda3\lib\site-packages\pymysql\_auth.py", line 252, in caching_sha2_password_auth
    data = sha2_rsa_encrypt(conn.password, conn.salt, conn.server_public_key)
  File "C:\programs\Anaconda3\lib\site-packages\pymysql\_auth.py", line 132, in sha2_rsa_encrypt
    rsa_key = serialization.load_pem_public_key(public_key, default_backend())
  File "C:\programs\Anaconda3\lib\site-packages\cryptography\hazmat\backends\__init__.py", line 15, in default_backend
    from cryptography.hazmat.backends.openssl.backend import backend
  File "C:\programs\Anaconda3\lib\site-packages\cryptography\hazmat\backends\openssl\__init__.py", line 7, in <module>
    from cryptography.hazmat.backends.openssl.backend import backend
  File "C:\programs\Anaconda3\lib\site-packages\cryptography\hazmat\backends\openssl\backend.py", line 53, in <module>
    from cryptography.hazmat.bindings.openssl import binding
  File "C:\programs\Anaconda3\lib\site-packages\cryptography\hazmat\bindings\openssl\binding.py", line 13, in <module>
    from cryptography.hazmat.bindings._openssl import ffi, lib
ImportError: DLL load failed: The specified module could not be found.

我发现 conda navigator（也不是 pip）没有从其标准通道中看到 ffi 包。

我已经尝试过这个建议（添加 conda-forge 频道）：

conda config --添加通道 conda-forge conda 安装 libffi

但是 conda 在“解决环境”中花费了很长时间，并且没有在合理的时间内给出答案。

我应该怎么做才能安装 ffi 并能够连接到数据库？我是世界上第一个在 Windows 上从 python/Anaconda 调用 mysql 的人吗？我想一定有解决办法。

谢谢，马可

Answer 1

我遇到了同样的问题。这就是为我解决的问题：

1. pip uninstall scrapy
2. conda uninstall scrapy
3. pip install --force --upgrade scrapy
4. scrapy startproject dingding

它有效。

Answer 2

我遇到了类似的错误：

File "/root/ncs/bootloader/mcuboot/scripts/imgtool.py", line 22, in <module>
    main.imgtool()
  File "/usr/lib/python3.7/site-packages/lib/python3.7/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3.7/site-packages/lib/python3.7/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3.7/site-packages/lib/python3.7/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/lib/python3.7/site-packages/lib/python3.7/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3.7/site-packages/lib/python3.7/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/root/ncs/bootloader/mcuboot/scripts/imgtool/main.py", line 111, in getpub
    key = load_key(key)
  File "/root/ncs/bootloader/mcuboot/scripts/imgtool/main.py", line 74, in load_key
    key = keys.load(keyfile)
  File "/root/ncs/bootloader/mcuboot/scripts/imgtool/keys/__init__.py", line 52, in load
    backend=default_backend())
  File "/usr/lib/python3.7/site-packages/cryptography/hazmat/backends/__init__.py", line 14, in default_backend
    from cryptography.hazmat.backends.openssl.backend import backend
  File "/usr/lib/python3.7/site-packages/cryptography/hazmat/backends/openssl/__init__.py", line 6, in <module>
    from cryptography.hazmat.backends.openssl.backend import backend
  File "/usr/lib/python3.7/site-packages/cryptography/hazmat/backends/openssl/backend.py", line 113, in <module>
    from cryptography.hazmat.bindings.openssl import binding
  File "/usr/lib/python3.7/site-packages/cryptography/hazmat/bindings/openssl/binding.py", line 14, in <module>
    from cryptography.hazmat.bindings._openssl import ffi, lib
ImportError: this module was compiled for Python 3.5

解决方案：

• 在

  _cffi_backend.cpython*.so

  和

  /usr/lib

   中搜索 

  /usr/local/lib

• 杀掉这些

  _cffi_backend.cpython*.so

• 在

  cffi

  和

  /usr/lib

   中搜索 

  /usr/local/lib
  目录

• 杀死这些目录

• pip3 install --force-reinstall cryptography

Answer 3

cryptography.hazmat.bindings 是不稳定的，人们可能需要查看来源。我求助于这样的非面向未来的代码：

try:
    from cryptography.hazmat.bindings._openssl import lib as libopenssl
except ImportError:
    from cryptography.hazmat.bindings._rust import _openssl
    libopenssl =  _openssl.lib