Paramiko: PKey.from_private_key_file unexpected keyword argument 'password' error

[qtfkwk]

To reproduce (from the Python interpreter):

import paramiko

# try 1: call class method directly
key = paramiko.pkey.PKey.from_private_key_file('path/to/key/file')

# try 2: call class method from PKey object instance
k = paramiko.pkey.PKey()
key = k.from_private_key_file('path/to/key/file')

Both of the examples above produce the error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/qtfkwk/.pyenv/versions/2.7.11/lib/python2.7/site-packages/paramiko/pkey.py", line 184, in from_private_key_file
    key = cls(filename=filename, password=password)
TypeError: __init__() got an unexpected keyword argument 'password'

According to the code in pkey.py, the from_private_key_file class method calls the __init__ method with the password argument... which is not one of the accepted arguments. In fact, the filename argument isn't an accepted argument either.

paramiko.pkey.PKey.__init__:

def __init__(self, msg=None, data=None):
    pass

paramiko.pkey.PKey.from_private_key_file:

@classmethod
def from_private_key_file(cls, filename, password=None):
    key = cls(filename=filename, password=password) # <=== problem is here
    return key

This seems like a bit of an oversight... perhaps I'm not doing it correctly. It would help if the documentation contained more examples. Please advise.

Pip reports that I have paramiko version 1.16.0. I am using Python 2.7.11.

[qtfkwk]

This works:

key = paramiko.RSAKey.from_private_key_file('path/to/key/file')

Looks like the class method is only intended to be called via a subclass of PKey, like RSAKey, whose __init__ method does allow the arguments.

[qtfkwk]

Through the magic of Python, this factory method (from_private_key_file) will exist in all subclasses of PKey (such as RSAKey or DSSKey), but is useless on the abstract PKey class.

-- http://docs.paramiko.org/en/1.16/api/keys.html