Forbid short selling

[yoghurtshawn]

Hi community,

Since short selling may be forbidden in markets like CHINA AShares, I was wondering if there were any settings in Backtrader ensuring that.

Many thanks!

[backtrader]

Don't sell too much and you won't short sell.

[yoghurtshawn]

It seems this LongOnly sizer could do the trick. Right?

class LongOnly(bt.Sizer):
    params = (('stake', 1),)

    def _getsizing(self, comminfo, cash, data, isbuy):
      if isbuy:
          return self.p.stake

      # Sell situation
      position = self.broker.getposition(data)
      if not position.size:
          return 0  # do not sell if nothing is open

      return self.p.stake

[backtrader]

That's only a patch which works if the position is 0 and only works if you don't manually specify the size which will trigger the usage of the sizer.

Let me insist: don't sell when not needed and you won't short.

It is really easy: if your code is selling (going to a minus position from either zero or a positive one) short ... your code has a problem.