Runtime Error: 'NoneType' object has no attribute 'Reset' at OnSecuritiesChanged

The error message "Runtime Error: 'NoneType' object has no attribute 'Reset'" typically means that you're trying to call the Reset method on an object that is None. This could happen if the symbolData object is not properly initialized before the Reset method is called.

In the OnSecuritiesChanged method, you should check if symbolData is None before calling Reset. Here is an example of how you can do this:

def OnSecuritiesChanged(self, algorithm, changes):  
    for added in changes.AddedSecurities:  
        symbolData = self.symbolDataBySymbol.get(added.Symbol)  
        if symbolData is None:  
            # create MA  
            symbolData = SymbolData(added)  
            symbolData.MA = CustomIndicator(added.Symbol, self.n1)  
            self.symbolDataBySymbol[added.Symbol] = symbolData  
        else:  
            # a security that was already initialized was re-added, reset the indicators  
            symbolData.MA.Reset()

In this code, symbolData is checked if it's None before calling Reset. If it's None, a new SymbolData object is created and added to symbolDataBySymbol dictionary. If it's not None, meaning the security was already initialized and re-added, the Reset method is called.

Please ensure that your code follows a similar pattern to avoid calling methods on None objects.

Hi Mia, Thanks for the quick response! I should've attached the code earlier.

    def OnSecuritiesChanged(self, algorithm, changes):
        '''Event fired each time the we add/remove securities from the data feed
        Args:
            algorithm: The algorithm instance that experienced the change in securities
            changes: The security additions and removals from the algorithm'''

        # clean up data for removed securities
        super().OnSecuritiesChanged(algorithm, changes)
        for removed in changes.RemovedSecurities:
            symbolData = self.symbolDataBySymbol.pop(removed.Symbol, None)
            symbolData.Reset()


        # initialize data for added securities
        symbols = [x.Symbol for x in changes.AddedSecurities]
        for symbol in [x for x in symbols if x not in self.symbolDataBySymbol]:
            self.symbolDataBySymbol[symbol] = self.MeanVarianceSymbolData(symbol, self.lookback, self.period)
        self.WarmUp(algorithm, symbols)

Unfortunately, I still get a run error at a specific point in time. When I use the code you replied I get a different run error:

Hi David,

The error you're encountering is due to the fact that you're trying to call the Reset method on an object that is None. This happens when the pop method doesn't find the removed.Symbol in the self.symbolDataBySymbol dictionary and returns None as a default value.

To fix this, you should check if symbolData is None before calling Reset. Here's how you can modify your code:

def OnSecuritiesChanged(self, algorithm, changes):
    super().OnSecuritiesChanged(algorithm, changes)
    for removed in changes.RemovedSecurities:
        symbolData = self.symbolDataBySymbol.pop(removed.Symbol, None)
        if symbolData is not None:
            symbolData.Reset()

In this modified code, symbolData is checked if it's None before calling Reset. If it's None, the code simply skips the Reset call. This should prevent the error you're seeing.

Remember to ensure that your securities are correctly initialized and added to the self.symbolDataBySymbol dictionary to avoid similar issues in the future.

The error message "Runtime Error: 'NoneType' object has no attribute 'Reset'" typically means that you're trying to call the Reset method on an object that is None. This could happen if the symbolData object is not properly initialized before the Reset method is called.

In your OnSecuritiesChanged method, you are calling Reset on symbolData without checking if it's None. Here is the problematic part of your code:

for removed in changes.RemovedSecurities:
    symbolData = self.symbolDataBySymbol.pop(removed.Symbol, None)
    symbolData.Reset()

You should check if symbolData is None before calling Reset. Here is an example of how you can do this:

for removed in changes.RemovedSecurities:
    symbolData = self.symbolDataBySymbol.pop(removed.Symbol, None)
    if symbolData is not None:
        symbolData.Reset()

In this code, symbolData is checked if it's None before calling Reset. If it's not None, the Reset method is called. This should help you avoid calling methods on None objects and fix your error.

Thank you very much! I will try to fit this into my code. I think I understand now.