Sure, just add `blank=True, null=True` for each field that you want to remain optional like 

    subject = models.ForeignKey(subjects, blank=True, null=True)

In order to accomplish this, the `on_delete` argument is necessary along with `blank=True` and `null=True`, and it would be better if you do it this way.

    subject = models.ForeignKey(subjects, on_delete=models.SET_NULL, blank=True, null=True)

`null=True`
&lt;hr&gt;


```
subject=models.ForeignKey(subjects, on_delete=models.CASCADE, default=None, blank=True, null=True)
```

**Field.null**

If True, Django will store empty values as NULL in the database. Default is False.

Avoid using null on string-based fields such as CharField and TextField. If a string-based field has null=True, that means it has two possible values for “no data”: NULL, and the empty string. In most cases, it’s redundant to have two possible values for “no data;” the Django convention is to use the empty string, not NULL. One exception is when a CharField has both unique=True and blank=True set. In this situation, null=True is required to avoid unique constraint violations when saving multiple objects with blank values.


I cannot find any examples of how to do this, but how can I add a box shadow only to the top and bottom of an element?

CSS Box Shadow - Top and Bottom Only

My webpage has a &#39;skinny&#39; list: for example, a list of 100 items of one word in length each. To reduce scrolling, I want to present this list in two or even four columns on the page. How should I do this with CSS?

&lt;!-- begin snippet: js hide: false --&gt;

&lt;!-- language: lang-html --&gt;

    &lt;ul&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
        &lt;li&gt;Item&lt;/li&gt;
    &lt;/ul&gt;

&lt;!-- end snippet --&gt;

I prefer the solution to be flexible so that if the list grows to 200 items, I don&#39;t have to do a lot of manual adjustments to accommodate the new list.

Is there a way to break a list into columns?

I have this code


    subject      = models.ForeignKey(subjects)
    location     = models.ForeignKey(location)
    publisher    =  models.ForeignKey(publisher)


There its not always possible that I have three values of books.
so sometimes if I don&#39;t know subject or location, or publisher. Then I want to keep them empty

But if I have then I need select box to select. is it possible like that

Can I make the foreign key field optional in Django model

I have this code
<pre><code class="hljs language-ini">subject = models.ForeignKey(subjects)
location = models.ForeignKey(location)
publisher = models.ForeignKey(publisher)
</code></pre>
There its not always possible that I have three values of books.
so sometimes if I don't know subject or location, or publisher. Then I want to keep them empty
But if I have then I need select box to select. is it possible like that

Can somebody explain me where the diferences are between Django and the Model View Controller pattern?

Functionally, what can we expect from those differences — i.e. what works differently comparing Django to, for example, Ruby on Rails?

Django vs. Model View Controller

Is there any way of using [get_object_or_404][1] and [select_related][2] together or any other way to achieve the result of using these two together(except from putting it in try/except)?? 


  [1]: https://docs.djangoproject.com/en/dev/topics/http/shortcuts/#get-object-or-404
  [2]: https://docs.djangoproject.com/en/dev/ref/models/querysets/#select-related

django : using select_related and get_object_or_404 together

I have built a site using Django and I am receiving this annoying error when I am trying to execute a query.

If I restart the Apache server, the error will go away for a short time.

    Traceback:
    File &quot;/usr/local/lib/python2.7/site-packages/django/core/handlers/base.py&quot; in get_response
    100.                     response = callback(request, *callback_args, **callback_kwargs)
    File &quot;/home/fran/cron/views/set_caches.py&quot; in set_caches
    24.         cursor.execute(query, [category[&#39;id&#39;]])
    File &quot;/usr/local/lib/python2.7/site-packages/django/db/backends/util.py&quot; in execute
    15.             return self.cursor.execute(sql, params)
    File &quot;/usr/local/lib/python2.7/site-packages/django/db/backends/mysql/base.py&quot; in execute
    86.             return self.cursor.execute(query, args)
    File &quot;build/bdist.linux-i686/egg/MySQLdb/cursors.py&quot; in execute
    155.         charset = db.character_set_name()

    Exception Type: InterfaceError at /blablabla/
    Exception Value: (0, &#39;&#39;)


InterfaceError (0, &#39;&#39;)

Hey i have looked around through some simliar posts here on SO but havent found anything that has solved my problem. I have the following models,

    from django.db import models
    
    class Areas(models.Model):
    
    	name =  models.CharField(max_length = 120)
    	order_in_sidebar_network = models.IntegerField(blank=True, null=True)
    	order_in_section_network = models.IntegerField(blank=True, null=True)
    
    
    	def __unicode__ (self):
    		return self.area_name
    
    	class Meta:
    		verbose_name_plural = &quot;Areas&quot;
    		verbose_name = &quot;Area&quot;
    
    class Countries(models.Model):
    	name = models.CharField(max_length = 120, help_text = &quot;The name of the country&quot;)
    	area = models.ForeignKey(Areas, verbose_name = &#39;Area&#39;)
    	
    	def __unicode__ (self):
    		return self.name
    
    	class Meta:
    		verbose_name_plural = &quot;Countries&quot;
    		verbose_name = &quot;Country&quot;
    		ordering = [&#39;name&#39;]
    
    
    
    class Offices(models.Model):
    	country = models.ForeignKey(Countries, verbose_name = &#39;Country&#39;)
    	name = models.CharField(max_length = 255, help_text = &quot;The name of this office, IE London&quot;)
    	main_office = models.BooleanField(default= False, help_text = &quot;Is this office a key location?&quot;, verbose_name = &quot;Key Location&quot;)
    	address_1 = models.CharField(max_length = 255, null = True, blank = True)
    	address_2 = models.CharField(max_length = 255, null = True, blank = True)
    	address_3 = models.CharField(max_length = 255, null = True, blank = True)
    	city = models.CharField(max_length = 255, null = True, blank = True)
    	postcode = models.CharField(max_length = 20)
    	tel = models.CharField(max_length = 30, null= True, blank = True, help_text = &quot;Optional telephone contact number&quot;)
    	mobile = models.CharField(max_length = 30, null= True, blank = True, help_text = &quot;Optional mobile contact number&quot;)
    	fax = models.CharField(max_length = 30, null= True, blank = True, help_text = &quot;Optional fax contact number&quot;)
    	data_1 = models.CharField(max_length = 255, null = True, blank = True, help_text = &quot;Optional additional data&quot;, verbose_name = &quot;Additional information&quot;)
    	data_2 = models.CharField(max_length = 255, null = True, blank = True, help_text = &quot;Optional additional data&quot;, verbose_name = &quot;Additional information&quot;)
    	
    	class Meta:
    		verbose_name_plural = &quot;Offices&quot;
    		verbose_name = &quot;Office&quot;
    		ordering = [&#39;name&#39;]
    	
    	def __unicode__(self):
    		return self.name
    	
    class OfficeMembers(models.Model):
    	name = models.CharField(max_length = 60, help_text = &quot;Please tell us this person name&quot;)
    	title = models.CharField(max_length = 100, help_text = &quot;The person&#39;s title, IE Managing Director&quot;)
    	email = models.EmailField(max_length = 255, null = True, blank = True, help_text = &quot;Optional email address for this person&quot;)
    	email2 = models.EmailField(max_length = 255, null = True, blank = True, help_text = &quot;Optional second email address for this person&quot;)
    	phone = models.CharField(max_length = 30, null = True, blank  = True, help_text = &quot;Optional contact number for this person&quot;)
    	mobile = models.CharField(max_length = 30, null = True, blank  = True, help_text = &quot;Optional mobile contact number for this person&quot;)
    	office = models.ForeignKey(Offices, null = True)
    	class Meta:
    		verbose_name_plural = &quot;Office Memebers&quot;
    		verbose_name = &quot;Office memebr&quot;
    		ordering = [&#39;name&#39;]
    
    	def __unicode__(self):
    		return self.name

i have the following view set up

    def index(request):
    	
    	cache_key = &quot;world_areas&quot;
    	cache_time = 60
    	
    	world_areas_cache = cache.get(cache_key)
    		
    	#if no cache is set, grab the objects, and set the cache
    	
    	logger.debug(world_areas)
    	if not world_areas_cache:
    		logger.info(&#39;No cache found grabbing objects&#39;)
    		world_areas = Areas.objects.select_related().all()
    		#cache.set(cache_key, world_areas, cache_time)
    		logger.debug(world_areas)
    	else:
    		logger.info(&quot;Getting from cache&quot;)
    		world_areas = world_areas_cache
    		
    	return render_to_response(&#39;network/index.html&#39;, {&#39;world_areas&#39;:world_areas}, context_instance=RequestContext(request))

trying to iterate over the world_areas object like so

    {% for area in world_areas %}
produces a template syntax error

&gt;  &#39;RelatedManager&#39; object is not iterable

Any one got any ideas why this is happeing? really cant seem to get round this! strangley this is working for me in shell :S am i missing something obvious???

Big thanks to anyone able to help!

&#39;RelatedManager&#39; object is not iterable Django

I am trying to access a `model.filefield` in Django to parse a [CSV][1] file in Python using the `csv` module. It&#39;s working on Windows, but on Mac it gave me this:

    Exception Type: Error

    Exception Value: new-line character seen in unquoted field - do you need to open the file in universal-newline mode?

This is the code:

    myfile = customerbulk.objects.all()[0].fileup

    mydata = csv.reader(myfile)
        for email,mobile,name,civilid in mydata:
            print email,mobile,name,civilid

  [1]: http://en.wikipedia.org/wiki/Comma-separated_values


Open the file in universal-newline mode using the CSV Django module

I&#39;m defining my Django models right now and I realized that there wasn&#39;t a `OneToManyField` in the model field types. I&#39;m sure there&#39;s a way to do this, so I&#39;m not sure what I&#39;m missing. I essentially have something like this:

    class Dude(models.Model):
        numbers = models.OneToManyField(&#39;PhoneNumber&#39;)
    
    class PhoneNumber(models.Model):
        number = models.CharField()

In this case, each `Dude` can have multiple `PhoneNumber`s, but the relationship should be unidirectional, in that I don&#39;t need to know from the `PhoneNumber` which `Dude` owns it, per se, as I might have many different objects that own `PhoneNumber` instances, such as a `Business` for example:

    class Business(models.Model):
        numbers = models.OneToManyField(&#39;PhoneNumber&#39;)

What would I replace `OneToManyField` (which doesn&#39;t exist) with in the model to represent this kind of relationship? I&#39;m coming from Hibernate/JPA where declaring a one-to-many relationship was as easy as:

    @OneToMany
    private List&lt;PhoneNumber&gt; phoneNumbers;

How can I express this in Django?  

How to express a One-To-Many relationship in Django?

My model:

    class Sample(models.Model):
        users = models.ManyToManyField(User)

I want to save both `user1` and `user2` in that model:

    user1 = User.objects.get(pk=1)
    user2 = User.objects.get(pk=2)
    sample_object = Sample(users=user1, users=user2)
    sample_object.save()

I know that&#39;s wrong, but I&#39;m sure you get what I want to do. How would you do it ?



How to create an object for a Django model with a many to many field?

Every time I enter in a new player in the Admin portion of Django I get an error message that says &quot;This field is required.&quot;. 

Is there a way to make a field not required without having to create a custom form? Can I do this within models.py or admin.py?

Here&#39;s what my class in models.py looks like.
    
    class PlayerStat(models.Model):
        player = models.ForeignKey(Player)
        
        rushing_attempts = models.CharField(
            max_length = 100,
            verbose_name = &quot;Rushing Attempts&quot;
            )
        rushing_yards = models.CharField(
            max_length = 100,
            verbose_name = &quot;Rushing Yards&quot;
            )
        rushing_touchdowns = models.CharField(
            max_length = 100,
            verbose_name = &quot;Rushing Touchdowns&quot;
            )
        passing_attempts = models.CharField(
            max_length = 100,
            verbose_name = &quot;Passing Attempts&quot;
            )

Thanks 


Content Type	Original Author	Original Content on Stackoverflow
Question	user1	View Question on Stackoverflow
Solution 1 - Django	Abid A	View Answer on Stackoverflow
Solution 2 - Django	Muhammad Zubair	View Answer on Stackoverflow
Solution 3 - Django	MD SHAYON	View Answer on Stackoverflow

Can I make the foreign key field optional in Django model

Django Problem Overview

Django Solutions

Solution 1 - Django

Solution 2 - Django

Solution 3 - Django

Is there a way to break a list into columns?

CSS Box Shadow - Top and Bottom Only

Attributions