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

【问题标题】：ffi library can't be loaded from cryptography.hazmat.bindings._opensslffi 库无法从 cryptography.hazmat.bindings._openssl 加载
【发布时间】：2018-11-06 11:42:39
【问题描述】：

我正在尝试使用 anaconda（python 3.7 64 位）和 pymysql 包在 Windows 10 上打开一个 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、密码和端口正确；主机应该是本地主机（如果我通过 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）在其标准频道中看不到 ffi 包。

我已经尝试过这个建议（添加 conda-forge 频道）：

conda config --add 通道 conda-forge conda 安装 libffi

但是 conda 在“解决环境”中需要很长时间，并且不会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

【问题讨论】：

标签： python mysql windows anaconda ffi

【解决方案1】：

我遇到了同样的问题。这是为我解决的问题： 1. pip uninstall scrapy 2. conda uninstall scrapy 3. pip install --force --upgrade scrapy 4. scrapy startproject dingding 它有效。

【讨论】：

谢谢，为我做了。

【解决方案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

解决办法：

在/usr/lib 和/usr/local/lib 中搜索_cffi_backend.cpython*.so
杀死这些_cffi_backend.cpython*.so
在/usr/lib 和/usr/local/lib 中搜索cffi 目录
杀死这些目录
pip3 install --force-reinstall cryptography

【讨论】：