My Macbook Pro went in to sleep mode when i next tried to use i had a black screen so i held down the power button it switched off when i switched macbook back on i could hear the fans and the power light come on too but still had the black screen so to fix this on my Macbook Pro i had to do this reset and it works great.
Fix Macbook Pro Black Screen

Completely turn off the Macbook buy holding down the power button.
Next hold down the cmd, option key P and R and press the power button. You will hear the startup sound and your screen will now be working, the Macbook Pro will boot up as normal after this.

I really hope this fixes your Macbook Pro Black Screen.