求助 Python 用 RSA 签名报错

import rsa signature = rsa.sign(code2, RSA_PRIVATE, 'SHA-1')

报错: Traceback (most recent call last): File "D:/paython/test.py", line 104, in <module> signature = rsa.sign(code2, RSA_PRIVATE, 'SHA-1') File "C:\Python27\lib\rsa\pkcs1.py", line 276, in sign keylength = common.byte_size(priv_key.n) AttributeError: 'str' object has no attribute 'n'

求助！