python：py2exe cryptography多後端無法初始化，沒有後端

Question

我在Windows 7 64位上使用python 2.7.11與py2exe 0.6.9，運行.exe文件後出現以下錯誤。

ValueError: Multibackend cannot be initialized with no backends.

If you are seeing this error when trying to use default_backend() please try uninstalling and reinstalling cryptography.

Answer 1

我寫了波紋管代碼，然後問題就解決了。

def patch_crypto_be_discovery(): 

""" 
Monkey patches cryptography's backend detection. 
Objective: support pyinstaller freezing. 
""" 

from cryptography.hazmat import backends 

try: 
    from cryptography.hazmat.backends.commoncrypto.backend import backend as be_cc 
except ImportError: 
    be_cc = None 

try: 
    from cryptography.hazmat.backends.openssl.backend import backend as be_ossl 
except ImportError: 
    be_ossl = None 

backends._available_backends_list = [ 
    be for be in (be_cc, be_ossl) if be is not None 
] 

patch_crypto_be_discovery()