How to change datablock value in game? (newbie)

#1 Datablocks are static and shared with all objects that use them so I would guess no. I could be wrong, however.

I would recommend changing a value on the player object itself rather than the datablock.

#2 Yeah, you can change it, but changing it would effect everybody using that datablock. I think you could just do PlayerBody.doubleJumpEnabled = true;

If you wanted to make it per-player, you would have to change that from being a datablock value to a Player value.

#3 Thank you Ben and Nathan. Actually, I will use this datablock for my main character only. but for my knowledge
can you guide me how to do like what you suggest. I don't know how to change datablock value to a player value. Do I have to mod the engine?

#4 I don't know whether it like this: %player.getDataBlock().doubleJumpEnabled = true;

#5 Or it might be PlayerBody.doubleJumpEnabled = true; I'm not sure which is right here though.