Thinking more…

最近需要做 public/private key 的加解密，所以找到 pycryptco 。

使用的例子可以參考 Python and cryptography with pycrypto

但使用時，卻遇到 unsupported operand type(s) for pow() 的問題，經過一番查找，才找到問題所在，詳情可以看這篇：Error with encrypt message with RSA python – Stack Overflow

主要是因為 Python 3 的字串預設是 unicode 字串，而 encrypt 沒辦法處理，所以得先 encode 為 utf-8 字串才行：

# -*- coding: utf-8 -*-
import os
import base64
from Crypto.PublicKey import RSA
from Crypto import Random
from Crypto.Cipher import PKCS1_OAEP, AES
from pprint import pprint


# Generate key
if os.path.exists('mykey.pem'):
    with open('mykey.pem', 'rb') as fin:
        key = RSA.importKey(fin.read())
else:
    random_generator = Random.new().read
    key = RSA.generate(1024, random_generator)
    with open('mykey.pem', 'wb') as fout:
        fout.write(key.exportKey('PEM'))

# Display key information
print("key = {}".format(key))
print("can_encrypt = {}".format(key.can_encrypt()))
print("can_sign = {}".format(key.can_sign()))
print("can_private = {}".format(key.has_private()))

# show public key
pprint(dir(key.publickey()))

# Encrypt
enc_data = key.publickey().encrypt("abcdef".encode('utf-8'), 32)
pprint(enc_data)

# Decrypt
print(key.decrypt(enc_data))

python2 的 sys.path 是

['',
 '/usr/local/lib/python2.7/dist-packages/python_nghttp2-1.3.5.dev0-py2.7-linux-x86_64.egg',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-x86_64-linux-gnu',
 '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old',
 '/usr/lib/python2.7/lib-dynload',
 '/home/ellery/.local/lib/python2.7/site-packages',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PILcompat',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/pymodules/python2.7',
 '/usr/lib/python2.7/dist-packages/ubuntu-sso-client',
 '/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode']

 

python3 的 sys.path 是

['',
 '/usr/local/lib/python3.4/dist-packages/onedrive_d-1.1.0dev-py3.4.egg',
 '/usr/local/lib/python3.4/dist-packages/daemonocle-0.8-py3.4.egg',
 '/usr/local/lib/python3.4/dist-packages/Send2Trash-1.3.0-py3.4.egg',
 '/usr/local/lib/python3.4/dist-packages/certifi-2015.11.20.1-py3.4.egg',
 '/usr/local/lib/python3.4/dist-packages/psutil-2.1.1-py3.4-linux-x86_64.egg',
 '/usr/lib/python3/dist-packages',
 '/usr/lib/python3.4',
 '/usr/lib/python3.4/plat-x86_64-linux-gnu',
 '/usr/lib/python3.4/lib-dynload',
 '/home/ellery/.local/lib/python3.4/site-packages',
 '/usr/local/lib/python3.4/dist-packages']

 

會發現兩邊的 $HOME/.local/lib/pythonX.Y/site-packages 順序是不一樣的，照理來說，應該是要以 $HOME/.local/lib/pythonX.Y/site-packages 為優先，這樣才有機會安裝最新版本的 package 而無需更動到系統的 package。

那該怎麼辦呢？這可以修改 /etc/python3.4/sitecustomize.py 來解決這問題。

在 /etc/python3.4/sitecustomize.py 的最後加入

import os
import sys

sys.path.insert(0,
        os.path.join(
            os.path.expanduser("~"),
            ".local",
            "lib",
            "python3.4",
            "site-packages"))

Python3 在執行前，會先執行這個檔案，這裡在 sys.path 串列最前面插入 $HOME/.local/lib/pythonX.Y/site-packages ，就能解決這問題了。

參考資料：

• http://stackoverflow.com/questions/30541245/order-of-imports-and-paths-in-sys-path-in-python-2-and-python-3