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Django display table in templates

I am using Django 2.0.1, and I have the following code:
Models.py:
class Category(models.Model):
category_name = models.CharField(max_length=50)
class CategoryItems(models.Model):
category_name = = models.ForeignKey(Categories, related_name='categoriesfk', on_delete=models.PROTECT)
item_name = models.CharField(max_length=50)
item_description = models.CharField(max_length=100)
Thereafter my views.py:
def data(request):
categories_query = Categories.objects.all()
category_items_query = CategoriesItems.objects.all()
return render_to_response("data.html",
{'categories_query': categories_query,'category_items_query': category_items_query}
In the template I'm trying to display all items for each category, for example, suppose there are 4 categorizes, e.g. Bicycle, then it display all items belonging to that category only. For example, as follows:
Category 1:
Category_Item 1,
Category_Item 2,
Category_Item 3,
and so on ...
Category 2:
Category_Item 1,
Category_Item 2,
Category_Item 3,
and so on ...
I have tried to write so many different for-loops, but they just display all items, I need it to show items only for that category, then for loop to next category and show items for that.

You don't need your category_items_query variable, just category_query:
{% for category in category_query %}
<b>{{ category.category_name }}</b><br />
{% for item in category.categoriesfk.all %}
{{ item.item_name }}<br />
{% endfor %}
{% endfor %}
Your related_name of categoriesfk is weird, it'd make more sense to be something like items.

What you need is two for loops with an if to check if the second loop should belong to the first.
Try this:
{% for category in categories_query %}
{% for category_item in category_items_query %}
{% if category_item.category_name == category %}
{# do something with category_item #}
{% endif %}
{% endfor %}
{% endfor %}
I believe it would be more clear if you named the ForeignKey in CategoryItems to just "category", instead of "category_name", since this field will have the category itself, not just it's name. Your "if" would then be more readable and make more sense:
{% if category_item.category == category %}
Hope it helps.

A few things,
Since your model name is already Category, your field names should be like name instead of category_name.
Model names must be singular, so it should beCategoryItem instead of CategoryItems
When you do a model_name.objects.all(), you do not get a query but a Queryset, make your variable names such that they describe what they do. Currently, categories_query is wrong. You could instead use category_qs.
Now, coming to your question, you require two for loops. One to loop through the categories and then one to loop through items in a particular category.
Something like,
for category in category_qs:
for item in category:
# Do something with item
You have the basic idea here, now you can convert it to real working code. Good luck!

Grouping data in template is not best idea as template should be logic free,
also good idea would be to use database capabilities and use select_related to query out related set
category_data = Category.objects.select_related('item').all()
afterwards you could do following in template
{% for category in category_data %}
{# print category #}
{% for item in category.items %}
{# print item #}
{% endfor %}
{% endfor %}

Django has a built-in regroup template tag for this functionality.
{% regroup category_items_query by category_name as categoryname_list %}
{% for category in categoryname_list %}
<strong>{{ category.grouper }}</strong><br>
{% for item in category.list %}
{{ item.item_name }}: {{ item.item_description }}<br>
{% endfor %}
{% endfor %}
You have to order your CategoryItems for this functionality to work.
category_items_query = CategoriesItems.objects.all().order_by('category_name')

Trying to understand Django's communication between view and template

(edited)
I come from a web2py background and find Django a much more complicated framework to learn and use than web2py.
After the first answer, I have adapted the description of my problem.
In my view I have:
def team(request):
hr = dict(name="Some Name", photo="/static/images/HR.jpg", url="http://some.website.com/?page_id=3602")
js = dict(name="Some Name2", photo="/static/images/JS.jpg", url="http://some.website.com/?page_id=3608")
context = {team:[hr,js]}
return render(request, "wos_2017_2/team.html", context)
In the template I have
<ul>
{% for person in context.team %}
<li> {{ person.name }} {{ person.photo }} {{ person.url }} </li>
{% endfor %}
</ul>
There is absolutely no output.
This works in normal python:
hr = dict(name="Some Name", photo="/static/images/HR.jpg", url="http://some.website.com/?page_id=3602")
js = dict(name="Some Name2", photo="/static/images/JS.jpg", url="http://some.website.com/?page_id=3608")
context = dict(team = [hr,js])
for i in context['team']:
print(i['name'], i['photo'], i['url'])
With output
Some Name /static/images/HR.jpg http://some.website.com/?page_id=3602
Some Name2 /static/images/JS.jpg http://some.website.com/?page_id=3608
Why am I not getting any result in Django?

Your first example is correct. Sadly you have a small typo in your first line of code:
hr = dict(name="Some Name, ...),
The line ends with a comma ,. Now hr is becomes a tuple with a single element: the dict. Without the comma this works:
{{ team.0.name }}
{{ team.1.name }}
With your updated answer you need to change context.team to team in your template:
{% for person in team %}
The context dictionary is 'unpacked' in the template.

I was not able to comment so I had to post an answer.
Only immutable data types can be used as keys, i.e. no lists or dictionaries can be used If you use a mutable data type as a key, you get an error message.Tuple as keys are okay.
With what i can tell is the problem is in your view code:
This
context = {team:[hr,js]}
should be this:
context = {"team":[hr,js]}
or
context = dict(team=[hr,js])

<ul>
{% for person in team %}
<li> {{ person.name }} {{ person.photo }} {{ person.url }} </li>
{% endfor %}
</ul>
Was the correct way to read the dictionary in the template.

grouping fields in django form

I want to render form grouping fields. Form actually is created dynamically according to incoming dictionary
for f in settings.FORM_BIG_FIELDS:
self.fields[f['id']] = eval(f['type'])(label=f['label'], required=f.get('required', True))
self.fields[f['id']].groupp = f.get('group', 1)
groupp attribute means appropriate group, then I try to render it like
{% regroup form.fields.values by groupp as field_group %}
{% for group in field_group %}
<div class="group_{{ group.grouper }}">
{% for field in group.list %}
<p>
{{ field.all }}
{{ field }}
</p>
{% endfor %}
</div>
{% endfor %}
But as output I get the following
<django.forms.fields.CharField object at 0xb527388c>
<django.forms.fields.IntegerField object at 0xb52738ec>
<django.forms.fields.ChoiceField object at 0xb527394c>
I have read that these are not the same as BoundField object. How to render fields or is there any other better approaches to group fields?

If you do not want use any additional libraries, then the most easy solution is to render them manually, i would say. Otherwise you will just spend alot of time repeating the functionality of the library i copied as comment to your post.
There is always the case that things should be DRY. But we build websites for the users and user cares little about how the form rendering in template is done. For this reason we have often created form templates manually like this:
<div class="something">
{{ form.fieldname.label_tag }}{{ form.fieldname }}
</div>
Easyest way to organise it saving you some time. And in my opinion it is not that bad either, since this is not very common when you need fields organised by fieldsets.

I know this question is rather old, but I am sure there are still people who can benefit from a simple solution:
Say you have a group name and list of members. You can define a self.fieldset in your form's init to be a dictionary of {'group_1': ['member_1', 'member_2', ... ], ... }. Once you attach this to the form, you can pass it to views and from there to the template:
In forms.py:
class MyForm:
def __init__(self, current_user, *args, **kwargs):
super(YourForm, self).__init__(*args, **kwargs)
self.field['group'].queryset = Group.objects.filter(user = current_user)
...
In views.py:
form = self.Form(current_user)
the_fieldsets = form.fieldset
c = {'form': search_form,
'fieldsets': the_fieldsets }
In your template:
{% for field in form %}
<tr>
<td>{{field.label_tag}}</td>
{% if field.name == 'group' %}
<td>
<select id='{{field.id}}' name='{{field.name}}'>
{% for k,v in fieldsets.items %}
<optgroup label = {{k.name}}>
{% for val in v %}
<option name='{{val}} value = {{val.id}}> {{val.name}} </option> # Note that the select needs to return 'id', so value has to be {{val.id}}
{% endfor %}
</optgroup>
{% endfor %}
</select>
</td>
{% else %}
<td>{{field}}</td>
{% endif %}
<td>{{field.help_text}}</td>
<td>{{field.errors}}</td>
</tr>
{% endfor %}

sort in jinja2 when attribute is not available

I have a set of articles (using pelican for generating static sites) which includes a category called hotels. I'd like to sort these hotels. The problem is that only the hotels have an attribute called 'city' while the other articles do not and this obviously leads to the following error:
Caught exception "'pelican.contents.Article object' has no attribute 'city'".
Here is the code I am using:
{% for article in articles|sort(attribute='city') %}
{% if article.category == 'hotels' %}
<a href="hotels/{{ article.slug }}.html">
<p>{{ article.title }}</p>
</a>
{% endif %}
{% endfor %}
Is there a way to check to see if the attribute exists and provide some default value so that it does not cause an error?

You may be able to move your if statement into your for loop as a filter:
for article in articles if article.category == 'hotels' | sort(attribute='city')

If you want to show only entries that have a 'city' attribute, and have that list sorted by 'city', do:
for article in articles|selectattr("city")|sort(attribute="city")

If you want to iterate over only the hotels, see Sean Vieira's answer. If you want to iterate over all articles, but have the hotels sorted while the rest are in arbitrary order, you can do it by using macros:
{% macro my_macro(article) %}
...
{% endmacro %}
{% for a in articles if a.category == 'hotels' | sort(attribute='city') %}
{{ my_macro(a) }}
{% endfor %}
{% for a in articles if a.category != 'hotels' %}
{{ my_macro(a) }}
{% endfor %}
This will include everything you defined in my_macro first for each hotel, in the desired order, then for each article that is not a hotel.

I found this page when was looking for a similar solution.
Eventually, I solved it a bit differently and it might be helpful for someone else.
In one of my templates for Pelican I added statistics collected by 'post_stats' plugin about approximate time to read. It looked like
~{{ article.stats['read_mins']|default("0") }} min read
But if the plugin is not loaded then the 'article' object doesn't have the 'stats' attribute and rendering fails.
Jinja has the builtin test for testing if a variable is defined.
So, I came up with this solution
~{{ article.stats['read_mins'] if article.stats is defined else "0" }} min read

flask and wtf - how can I direct tag attributes for fields?

After fiddling with wtforms, fields use widgets to actually render them to html. I wrote some custom field/widget to draw html in a way that I'd more like to. But here's a question:
suppose I want to render them with pre-defined css class or give actual details myself.
How can I achieve this? and on what phase of handling requests(at Form class declaration? or when setting attributes to give Form some Fields? or when I'm actually calling them in jinja2 templates) I should do that?

I use a Jinja macro something like this:
{% macro field_with_errors(field) %}
{% set css_class=kwargs.pop('class', '') %}
{% if field.type in ('DateField', 'DateTimeField') %}
{{ field(class='date ' + css_class, **kwargs) }}
{% elif field.type == 'IntegerField' %}
{{ field(class='number ' + css_class, **kwargs) }}
{% else %}
{{ field(class=css_class, **kwargs) }}
{% endif %}
{% if field.errors %}
<ul class="errors">{% for error in field.errors %}<li>{{ error|e }}</li>{% endfor %}</ul>
{% endif %}
{% endmacro %}
usage is something like:
{{ field_with_errors(form.foo, placeholder='bar') }}
This lets me avoid boilerplate, but also lets me keep the display decisions in the template space.

Have a look at the rendering fields section.
Alternatively, you can add attributes to be rendered in the Jinja2 (etc.) template:
<div class="input-prepend">
{{ form.address(placeholder="example.com", id="address", autofocus="autofocus", required="required") }}
</div>
There's nothing to prevent you from using a variable for the ID value above, instead of address, then rendering the template with a keyword argument to populate it.