simulation places infinite orders if lead time is too long

[tycerch]

I'm a beginner at simpy and python, but maybe this will help someone else that is having this problem with an otherwise excellent package.

When I increased the lead time the simulation would create too many orders.

To fix it I added this variable self.num_ordered = 0.

changed this line in def review_inventory if self.level <= self.reorder_point and self.num_ordered == 0:

and added these two lines in def place_order, the order matters

self.num_ordered += units  #add this
yield env.timeout(lead_time)
# update inventory level and costs
self.update_cost(env)
self.level += units
self.num_ordered -= units #add this