How to access a dictionary element in a Django template

Question

I would like to print out the number of votes that each choice got  I have this code in a template       for choice in choices          choice choice   -   votes choice id     lt br   gt     endfor      votes is just a dictionary while choices is a model object   It raises an exception with this message    Could not parse the remainder

User · Answer

Similar to the answer by  russian spy     lt ul gt     for choice in choices items        lt li gt   choice 0   -   choice 1   lt  li gt     endfor     lt  ul gt    This might be suitable for breaking down more complex dictionaries

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Could find nothing simpler and better than this solution  Also see the doc   register filter def dictitem dictionary  key       return dictionary get key   But there s a problem  also discussed here  that the returned item is an object and I need to reference a field of this object  Expressions like     schema dict dictitem schema code  name    are not supported  so the only solution I found was     with schema schema dict dictitem schema code         lt p gt Selected schema     schema name    lt  p gt     endwith     UPDATE   register filter def member obj  name       return getattr obj  name  None   So no need for a with tag     schema dict dictitem schema code member  name

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choices     key1   val1    key2   val2     Here s the template    lt ul gt     for key  value in choices items        lt li gt   key   -   value   lt  li gt     endfor     lt  ul gt    Basically   items is a Django keyword that splits a dictionary into a list of  key  value  pairs  much like the Python method  items    This enables iteration over a dictionary in a Django template

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you can use the dot notation      Dot lookups can be summarized like   this  when the template system   encounters a dot in a variable name    it tries the following lookups  in   this order          Dictionary lookup  e g   foo  bar      Attribute lookup  e g   foo bar    Method call  e g   foo bar      List-index lookup  e g   foo 2           The system uses the first lookup type   that works  It   s short-circuit logic

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Use Dictionary Items      for key  value in my dictionay items       lt li gt    key         value    lt  li gt     endfor

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Ideally  you would create a method on the choice object that found itself in votes  or create a relationship between the models  A template tag that performed the dictionary lookup would work  too

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You need to find  or define  a  get  template tag  for example  here   The tag definition    register filter def hash h  key       return h key    And it   s used like      for o in objects       lt li gt    dictionary hash o id    lt  li gt     endfor

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You could use a namedtuple instead of a dict   This is a shorthand for using a data class  Instead of person     name     John    age    14      do  from collections import namedtuple Person   namedtuple  person     name    age    p   Person name  John   age 14  p name    John   This is the same as writing a class that just holds data  In general I would avoid using dicts in django templates because they are awkward

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To echo   extend upon Jeff s comment  what I think you should aim for is simply a property in your Choice class that calculates the number of votes associated with that object  class Choice models Model       text   models CharField max length 200       def calculateVotes self           return Vote objects filter choice self  count        votes   property calculateVotes   And then in your template  you can do     for choice in choices          choice choice   -   choice votes    lt br   gt     endfor     The template tag  is IMHO a bit overkill for this solution  but it s not a terrible solution either  The goal of templates in Django is to insulate you from code in your templates and vice-versa  I d try the above method and see what SQL the ORM generates as I m not sure off the top of my head if it will pre-cache the properties and just create a subselect for the property or if it will iteratively   on-demand run the query to calculate vote count  But if it generates atrocious queries  you could always populate the property in your view with data you ve collected yourself

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django template filter filter name get value from dict     your dict get value from dict your key

[python] How to access a dictionary element in a Django template?

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