Django Template: Dynamic template variable inside another variable

Question

I hope this makes sense... I am building a crypto asset list page (easy); however, in the {% for %} loop I would like to include a variable inside a variable. Showing the code will make more sense:

Tempalte.html

{% for crypto_asset in objects__list_cryptoAssets %}
   <tr role="row" class="body-row">
      <td role="cell">{{ api_external_prices.bitcoin.usd }}</td>
   </tr>
{% endfor %}

So the {% for %} loop grabs all the crypto assets and then I can use Django template {{ asset_class.slug }} to grab all slugs... nothing exceptional here. This variable {{ api_external_prices.bitcoin.usd }} grabs external USD prices for Bitcoin, {{ api_external_prices.bitcoin.eur }} prices in EUR, and so forth... nothing exceptional here either.

Here is where the question comes :: the idea would be to have something like {{ api_external_prices.{{ asset_class.slug }}.usd }}... so each crypto would have its own price FX fetched correctly. Is it possible to have a variable inside a variable?

Erik Kalkoken · Accepted Answer · 2022-06-11 17:41:24Z

1

They are several ways you can implement this:

Template filters

You can create a template filter api_external_prices that takes asset_class and the crypto type as parameters and returns the value.

The syntax would be something link this, where api_external_prices is the name of the template filter:

{{ asset_class|api_external_prices:"usd" }}

See here for more info about this feature: https://docs.djangoproject.com/en/4.0/howto/custom-template-tags/#writing-custom-template-filters

Methods

Another approach would be to have api_external_prices as method on your asset_class object, which returns an object that has a usd property. api_external_prices here can just be a wrapper that calls a central module/function, but this would make it much easier to use it in templates.

{{ asset_class.api_external_prices.usd }}

The first approach is similar to what you are asking, but personally I would prefer to use the 2nd approach, because it saves you from introducing as template filter.

answered Jun 11, 2022 at 17:41

Erik Kalkoken

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3 Comments

Marcos Benvenuto Over a year ago

Thank you very much for your answer. I would love to understand more about the implementation of the second method... I will put the remaining code to understand how you would tackle method 2

Erik Kalkoken Over a year ago

hmm. I thought all the data was coming from models, but now I see that you are fetching some of it in the view. That will make it difficult to apply any of the two solutions.

Erik Kalkoken Over a year ago

A third approach would be to create a data structure in the view that let's you access everything you need in the template. I would just try to map everything into a big list of nested dicts. e.g. the top dict representing the crypt assets and then each having a dict of prices by unit.

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