let's talk about size before breeding

What are the chances that my 531g 16 month old female python will grow into breeding age by the start of breeding season in Nov.?

I would think that gaining 1000 grams in 9-10 months might be a bit of a stretch. But, you never know. Just see how she is in November, and if she's not ready, give her another year to mature.

do they have to start in november?

No - they can start any time - some breeders breed year round.

that's what i wanted to know. I'd like to breed like that because I don't think she'll make 1500 by november.

:hijackd:
Do you have to give males cycle time if say you are breeding him to two or three females that are breeding at different times in the year?

Is it generally good practice to get all snakes in a collection on the same cycle as I've heard they can sense when a female nearby is ovulating and this causes some snakes to fast for a while?

When is the male mature enough to breed?

I am seeing you have a 16 month old snake that is only 500 ish grams - either that is a misprint or you have one slow growing or underfed snake.

Lets start with clarifying that first.

could have gone off its food also

Sounds small to me too. Should be twice that size.