can not identify

Question

snake   We live in south central Oklahoma we have had lots of rain lately found this snake coming in the house it is black with a button we are curious to see if you can help identify it and if it is poisonous?

Answer
I'm not able to ID this one by this pic alone.  I'm a little stumped by the "button" you mention. I'm assuming you're talking about a button like on a rattlesnake.  Is that correct?  The head does not seem wide enough for this to be a rattlesnake, nor do I know of a jet black species of rattlesnake.  Perhaps there is just a piece of skin trapped on the end of the tail???  That happens sometimes.

Also is this the only pic you have?  I'd like to see the head a little closer and a shot of the belly if you have one.  

If I had to guess from this pic alone I'd say Mexican black king snake, but Oklahoma is not listed as part of it's natural range. They are fairly popular as pets so it's possible you found someone's lost pet.  It's also possible the range needed to be expanded (Arizona is in it's range). It could also be an indigo snake and there quite a few other "harmless" options.  

Please send me further pics if you have them!!!  I love a challenge.