Python Programming with Piston: How to set a login key using Python (not the piston executable)

I am writing a python3/gtk+-3.0 app and I will be making posts as I find resolutions to issues I run into as I seek to do things with the piston library that are not yet documented. @xeroc, or others who are interested, do follow my blog and I will make posts tagged with #piston that you can pick through to gather the information. I know that others with knowledge of Python who want to write Steem based apps, simple examples being a Steem wallet using a Qt interface, or a complete Steem viewer (Mine will be targeting Gtk+-3.0) can use this information to build such an application.

I am working from the excellent piston library that you can install using pip3. You can find instructions for how to do this from @xeroc's blog, and there is the beginnings of documentation available from locations you can find on his blog.

In the example below, in order to perform a check to certify that a key is valid, a second import has to be done to acquire the calls and exceptions from the piston.wallet code. The example below I am using a data store backed from dconf to store the WIF (login key) code. The script attempts to create a Steem object using this key, and if the WIF is invalid, where you would put the code you run when the test is successful I have a simple print command, and conversely, if it fails, there is another print command that notifies you of this case also.

Note that there is an additional import that needs to be done that creates a namespace for the piston.wallet codebase.

from piston.steem import Steem
from piston import wallet as Wallet
# ...
    def test_login (self, window, settings):
        wif = settings.get_string("wif")
        try:
            steem_account = Steem(wif=wif)
        except Wallet.InvalidWifError:
            print ("invalid wif")
        else:
            print ("wif accepted")