Ball python opening his mouth when being handled?

I've had my guy for about 5 or 6 months and he has never stuck at me, but twice in the last few weeks he has opened his mouth like he is baring his teeth or something while I have been holding him, anyone familiar with this behavior?

He's probably yawning, which is perfectly normal for BPs.

Ok, awesome, I wasn't sure if they yawned or not. I'm not afraid of being bitten I was just worried that he might be becoming more aggressive towards me for some reason.