TypeError: _get_credit_interest() takes 6 positional arguments but 7 were given??

Nicola Prada

Hello,
I am subclassing _get_credit_interest() as explained in the documentation with the goal to use it to take care of dividends but in runtime I get a TypeError:

class CommInfo_Stocks(bt.CommInfoBase):
    params = (
      ('percentage',0.019),
      ('min', None),  
      ('max', None), 
      ('stocklike', True),
      ('commtype', bt.CommInfoBase.COMM_PERC),
      ('interest_long', True)
    )

    def _getcommission(self, size, price, pseudoexec):
        
        if self.params.percentage is None or self.params.percentage == 0:
            return 0
        
        commission = abs(size) * price * self.params.percentage
        
        if self.params.min is not None and commission < self.params.min:
            commission = self.params.min
            
        if self.params.max is not None and commission > self.params.max:
            commission = self.params.max

        return commission
    
    def _get_credit_interest(self, size, price, days, dt0, dt1):
        print('Log Something')
        return 0

This is the log of the error, any hint to fix this?

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-45-57f80c4d0e3d> in <module>
     59 
     60 # Run
---> 61 results = cerebro.run()
     62 
     63 # Statistics

~\AppData\Local\Continuum\anaconda3\lib\site-packages\backtrader\cerebro.py in run(self, **kwargs)
   1125             # let's skip process "spawning"
   1126             for iterstrat in iterstrats:
-> 1127                 runstrat = self.runstrategies(iterstrat)
   1128                 self.runstrats.append(runstrat)
   1129                 if self._dooptimize:

~\AppData\Local\Continuum\anaconda3\lib\site-packages\backtrader\cerebro.py in runstrategies(self, iterstrat, predata)
   1291                     self._runonce_old(runstrats)
   1292                 else:
-> 1293                     self._runonce(runstrats)
   1294             else:
   1295                 if self.p.oldsync:

~\AppData\Local\Continuum\anaconda3\lib\site-packages\backtrader\cerebro.py in _runonce(self, runstrats)
   1686                         return
   1687 
-> 1688             self._brokernotify()
   1689             if self._event_stop:  # stop if requested
   1690                 return

~\AppData\Local\Continuum\anaconda3\lib\site-packages\backtrader\cerebro.py in _brokernotify(self)
   1358         notification to the strategy
   1359         '''
-> 1360         self._broker.next()
   1361         while True:
   1362             order = self._broker.get_notification()

~\AppData\Local\Continuum\anaconda3\lib\site-packages\backtrader\brokers\bbroker.py in next(self)
   1194                 comminfo = self.getcommissioninfo(data)
   1195                 dt0 = data.datetime.datetime()
-> 1196                 dcredit = comminfo.get_credit_interest(data, pos, dt0)
   1197                 self.d_credit[data] += dcredit
   1198                 credit += dcredit

~\AppData\Local\Continuum\anaconda3\lib\site-packages\backtrader\comminfo.py in get_credit_interest(self, data, pos, dt)
    270 
    271         return self._get_credit_interest(data, size, price,
--> 272                                          (dt0 - dt1).days, dt0, dt1)
    273 
    274     def _get_credit_interest(self, data, size, price, days, dt0, dt1):

TypeError: _get_credit_interest() takes 6 positional arguments but 7 were given

vladisld

In CommInfoBase class (the one your class is derived from) the _get_credit_interest is defined as:

def _get_credit_interest(self, data, size, price, days, dt0, dt1):

You are missing the data parameter.

Nicola Prada

Thanks, I hadn't noticed that in the examples in the documentation the subclassing is from CommissionInfo and not CommInfoBase and the signature of _get_credit_interest is different between the two methods!