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Basic (I think) Question About Variables
Aitor Bazo
posted Feb 8, 2016
API Seeking Help Getting Started Using Data Tools and Tips

I've been trying to create a variable that is defined at all times but changes ocasionally and stays redefined throughout the entire backtest unless it's changed again. The problem is that either the variable needs to be set in initialize and cannot be changed later or needs to be set in handle data and will be reset every minute or day.

Basically, what I need is the following:

Define variable A
If event happens, define variable B
Replace A with B

or

Define variable A
If event happens, define variable B
If B is defined, use B instead of A

I feel like there's a simple solution I'm not seeing. Could anyone lend me a hand?

Thanks,
Aitor

3 responses
Simon Thornington
Feb 8, 2016

Well, you can put the variable in context, and only change it when the event happens (which you will have to detect in handle_data). Is that what you mean?

Jamie McCorriston
Feb 8, 2016

Hi Aitor,

Simon is right, you'll want to use the context object. Take a look at this tutorial video for a quick explanation!

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Aitor Bazo
Feb 8, 2016

Worked! Thanks! It turns out I wasn't using indentation on the variable definition (Duh) so, the variable was not really inside initialize. By the way, Jamie, I haven't figured out the beta calculation yet but I'm still trying. Sorry for not writing back, I've been a mess lately.

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The material on this website is provided for informational purposes only and does not constitute an offer to sell, a solicitation to buy, or a recommendation or endorsement for any security or strategy, nor does it constitute an offer to provide investment advisory services by Quantopian.

In addition, the material offers no opinion with respect to the suitability of any security or specific investment. No information contained herein should be regarded as a suggestion to engage in or refrain from any investment-related course of action as none of Quantopian nor any of its affiliates is undertaking to provide investment advice, act as an adviser to any plan or entity subject to the Employee Retirement Income Security Act of 1974, as amended, individual retirement account or individual retirement annuity, or give advice in a fiduciary capacity with respect to the materials presented herein. If you are an individual retirement or other investor, contact your financial advisor or other fiduciary unrelated to Quantopian about whether any given investment idea, strategy, product or service described herein may be appropriate for your circumstances. All investments involve risk, including loss of principal. Quantopian makes no guarantees as to the accuracy or completeness of the views expressed in the website. The views are subject to change, and may have become unreliable for various reasons, including changes in market conditions or economic circumstances.