Can you do a full backtest and then attach the backtest to your reply? That will share with us the source code you are trying to use.

Here is some information from the help page: https://www.quantopian.com/help#ide-sid-lookup

Thank you for your reply. I find if after I enter the sid, I change the symbol manually wherever a symbol appears in the formula, it works. Does this seem to make sense. i.e goog is the sid, I manually enter goog at lines 34,37,43,51,53.

Hi August, I don't know what those line number are. Please share the source code (by attaching a backtest).

   # security ID  
  context.ma = sid(32146)  

    context.max_notional = 1000000.1  
  context.min_notional = -1000000.0

def handle_data(context, data):  

   vwap = data[context.ma].vwap(50)  
    price = data[context.ma].price  


  notional = context.portfolio.positions[context.ma].amount * price  

    if price < vwap * 0.995 and notional > context.min_notional:  
    order(context.ma,-100)  
  elif price > vwap * 1.005 and notional < context.max_notional:  
    order(context.ma,+100)  
Does this help?  

@August, you can edit your post (use the pencil icon) and use "Code Sample - Ctrl-K" to format the code block.

# This is a code sample  

Now to answer your question. When you use the sid() function you are getting a stock symbol from an identifier number. You can get information about that stock:

# price of GOOG  
price = data[sid(26578)].price  

If you set a variable (context.goog) to sid(26578) you don't have to re-type it all over the place and possibly make a mistake in the number.

# GOOG  
context.goog = sid(26578)

# price of GOOG  
price = data[context.goog].price  

In the example you pasted the variable is context.ma and is set to sid(32146) for MA (Mastercard)

But you don't have to name the variable after the stock symbol.

context.mystock = sid(26578)  
price = data[context.mystock].price  

Does that make sense?

Yes it does and thank you very much for the help. I have many years as a professional money manager. But now I'm trying to update myself. Very difficult for an "OLD" pro.