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POCheck for multiple values in a M2M relationship in Django
 

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  1. POCheck for multiple values in a M2M relationship in Django
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    <p>In English, I want to check whether a user's type is either a viewer, a moderator, or an administrator.</p> <p>Here is the relevant part of my <code>models.py</code></p> <pre><code>class UserType( models.Model ) : name = models.CharField( max_length = 135 ) # id | name #----+------------------ # 1 | tenant # 2 | property manager # 3 | property owner # 4 | vendor manager # 5 | vendor # 6 | viewer # 7 | moderator # 8 | administrator class UserProfile( models.Model ) : user = models.OneToOneField( User ) user_types = models.ManyToManyField( UserType, null = True, blank = True ) </code></pre> <p>By the way, I set <code>user.profile</code> to be the same thing as <code>user.get_profile()</code>.</p> <p>In my <code>views.py</code> code, I want to do the checking. I figured out that</p> <pre><code>[ user_type.pk for user_type in user.profile.user_types.all() ] </code></pre> <p>will give me a list of <code>pk</code>'s for the <code>user</code>'s <code>user_type</code>, like so <code>[ 1, 2, 6 ]</code>. Meaning that this particular user is a tenant (1), property manager (2), and a viewer (6).</p> <p>If I just want to check one <code>user_type</code>, then I can simply do</p> <pre><code>if 6 in [ user_type.pk for user_type in user.profile.user_types.all() ] : # This user is a viewer </code></pre> <p>But how can I check multiple user_types/pks? I wanted to do something like</p> <pre><code># This won't work if [ 6, 7, 8 ] in [ user_type.pk for user_type in user.profile.user_types.all() ] : # This user is either a viewer, moderator, or administrator </code></pre> <p>Also is my method of list comprehension to check <code>user_types</code> the <strong>Django-way</strong>? It doesn't seem like it, but I couldn't figure out how to query it <em>cleanly</em> in Django.</p> <p>Any tips and suggestions welcomed. Thanks in advance!</p> <p><strong>EDIT:</strong></p> <p>I just figured out I can list pks the more Django-way with <a href="https://docs.djangoproject.com/en/dev/ref/models/querysets/#values-list" rel="nofollow"><code>values_list</code></a></p> <pre><code>user_types = user.profile.user_types.values_list( 'pk', flat = True ) # [ 1, 2, 6 ] </code></pre> <p>I also figured out that I <em>could</em> check multiple values like this</p> <pre><code>if len( set( [ 1, 9 ] ).intersection( set( user_types ) ) ) # True because of 1 is in user_types (don't care about 9) if len( set( [ 4, 99 ] ).intersection( set( user_types ) ) ) # False because 4 nor 99 is in user_types </code></pre> <p>But even this <code>set</code> method doesn't seem very Django-friendly. There must be an easier way right?</p>
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