This is a little female Nelsons Milk Snake. Beautiful bands that are wider than usual for a Nelsons milk, but ver beautiful nonetheless. 

Species:   Lampropeltis Triangulum Nelsoni
Common Name:   Nelson’s Milk Snake
Care Level:    Beginner/Intermediate
Lifespan:   10+ years
Adult Size:   Up to 5 feet
Captive Diet:   Frozen/thawed mice
Adult Minimum Tank Size:   30 gallons
Temperature & Humidity:   70-85 degrees