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POCan't modify object by index in evaluated queryset with Django
 

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  1. POCan't modify object by index in evaluated queryset with Django
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    <p>I manage the order of <code>Documents</code> in a <code>Collection</code> by assigning ordinal numbers to <code>DocumentMemberships</code>, which is the model that represents an intersection of a <code>Document</code> and a <code>Collection</code>. Here is one place that I do this (this is inside a method of <code>Collection</code>):</p> <pre><code>memberships = self.membership_set.order_by('document__title', 'document__revision').all() for i in range(memberships.count()): if memberships[i].document.category == 'SDS': memberships[i].ordinal = i + 1000 # push documents in the 'SDS' category to the end else: memberships[i].ordinal = i # leave the rest ordered by title and then revision memberships[i].save() </code></pre> <p>However, when I inspect the <code>DocumentMemberships</code> in the admin interface after running this code, all the ordinals are zero (the default for that field). </p> <p>I tracked the issue down to the objects in the QuerySet not being properly modified when accessed by index. This is a shell session that more clearly demonstrates the issue:</p> <pre><code>&gt;&gt;&gt; memberships = s.membership_set.order_by('document__title', 'document__revision').all() &gt;&gt;&gt; memberships.all() [large number of DocumentMembership objects] &gt;&gt;&gt; memberships[0] [DocumentMembership object] &gt;&gt;&gt; memberships[0].ordinal = 2 &gt;&gt;&gt; memberships[0].ordinal 0 </code></pre> <p>The ordinals have to be fully computed as integers before further processing so I can't simply iterate over it. Did I miss something?</p>
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    1. USAndrew Buss
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