I'm trying to add some values from another list synchronously in the for loop of django ’s template. When I use a given number everything works fine, but when I replace it to {{forloop.counter}} it reports an error slice requires 2 arguments, 1 provided
I Googled it and the suggestion is that there should be no spaces in the code, but there are no spaces in my code, here the code in question.
{% for i in invtypes %}
<li>
...
<p>{{data|slice:":{{forloop.counter}}"}}</p>
</li>
{% endfor %}
The {{data}} is a list of extra data for invtypes so they have same length and sort。
I added a colon after slice to fix the error.
Before:
{{ post.body|slice":200" }}
After:
{{ post.body|slice:":200" }}
The problem is that in the line {{data|slice:":{{forloop.counter}}"}} the ":{{forloop.counter}}" would not work as you expect as if it were performing string interpolation. What can be done to get around this is to use the with template tag along with the add and stringformat template filters to get the required value as a template variable before you try to render that:
{% for i in invtypes %}
<li>
...
{% with str_counter=forloop.counter|stringformat:"i" %}
{% with slice_var=":"|add:str_counter %}
<p>{{ data|slice:slice_var }}</p>
{% endwith %}
{% endwith %}
</li>
{% endfor %}
One should also note that a need to do this implies that the view is not supplying the data to the template in an efficient manner, ideally the template should not be doing all of this manipulation with data. It can be seen that invtypes and data have some type of relationship but the context given by the view does not convey that at all.
I had the same problem and the solutions seems to be spaces indeed.
Try:
{% for i in invtypes %}
<li>
...
<p>{{ data|slice:":{{ forloop.counter }}" }}</p>
</li>
{% endfor %}
and see how that goes.
I found the correct solution.
(Wrong) =>
{{data|slice: ":{{forloop.counter}}"}}
[don't add a space after slice's colon.
(Right) =>
{{data|slice:":{{forloop.counter}}"}}
If you add a space after slice's colon, it takes only the part which comes before that space and considered it as one argument and second one will be considered as missing.
Related
With this code:
{% for o in [1,2,3] %}
<div class="{% cycle 'row1' 'row2' %}">
{% cycle 'row1' 'row2' %}
</div>
{% endfor %}
I get a TemplateSyntaxError:
Could not parse the remainder: '[1,2,3]' from '[1,2,3]'
Is there a way of building a list in a template?
We can use split method on str object :
page.html :
{% with '1 2 3' as list %}
{% for i in list.split %}
{{ i }}<br>
{% endfor %}
{% endwith %}
Results :
1
2
3
You can do it via cunning use of the make_list filter, but it's probably a bad idea:
{% for o in "123"|make_list %}
<div class="{% cycle 'row1' 'row2' %}">
{% cycle 'row1' 'row2' %}
</div>
{% endfor %}
p.s. You don't seem to be using o anywhere, so I'm not sure what you're trying to do.
I made this template tag to achieve this goal.
from django import template
register = template.Library()
# use #register.assignment_tag
# only when you're working with django version lower than 1.9
#register.simple_tag
def to_list(*args):
return args
to use it in template:
{% load your_template_tag_file %}
{% to_list 1 2 3 4 5 "yes" as my_list %}
{% for i in my_list %}
{{ i }}
{% endfor %}
Reference here:
Django simple tags
The other answers here look like the ticket (at least for what I wanted), so I'll provide an answer as to WHY you might want to do something like this (and perhaps there's a better answer for my case than what's been provided):
I came across this question looking for a way to build 3 very similar, but not identical buttons using Bootstrap. One button might look like
<div class="btn-group">
<a class="btn btn-primary dropdown-toggle" data-toggle="dropdown" href="#">
Modality
<span class="caret"></span>
</a>
<ul class="dropdown-menu" id="Modality">
<li>Action</li>
</ul>
</div>
where the difference between buttons is limited to the text of the button (Modality, on its own line above) and the contents of the pertaining to the button, which we'll assume is filled dynamically by JS (referencing id="Modality").
If I need to make 10 of these, copy/pasting the HTML seems dumb and tedious, especially if I want to change anything about my button after the fact (like making all of them split-drop-downs) and it goes against DRY.
So, instead, in the template I could do something like
{% with 'Modality Otherbutton Thirdbutton' as list %}
{% for i in list.split %}
<!-- copy/paste above code with Modality replaced by {{ i }} -->
{% endfor %}
{% endwith %}
Now, granted, in this particular case the buttons add functionality to some related data grid, so the button names could be dynamically filled from django model-sourced data as well, but I'm not at that stage in my design right now, and you can see where this sort of functionality is desirable to maintain DRY.
The simplest is to do
{% for x in "123" %}
drodger is correct, you can't do that in the deliberately-crippled Django template lanuage. Either pass in the list as a context variable when you invoke the template or try a template tag like expr. Then you can say {% expr [1,2,3] as my_list %} and then use my_list in your for loop.
This maybe an inspiration. Use the buildin filter add.
{{ first|add:second }}
first is [1, 2, 3] and second is [4, 5, 6], then the output will be [1, 2, 3, 4, 5, 6].
This filter will first try to coerce both values to integers.
If this fails, it'll attempt to add the values together anyway.
This will work on some data types (strings, list, etc.) and fail on others.
If it fails, the result will be an empty string.
The official specification,https://docs.djangoproject.com/zh-hans/2.0/ref/templates/builtins/#built-in-filter-reference
I have recently started to learn Django, so I came across with some HTML templates, but those are pretty unfamiliar for me, they mostly consist of {% and {{
For example:
<h1>{{ question.question_text }}</h1>
<ul>
{% for choice in question.choice_set.all %}
<li>{{ choice.choice_text }} -- {{ choice.votes }} vote{{ choice.votes|pluralize }}</li>
{% endfor %}
</ul>
Vote again?
What are they? Implementations from other languages or HTML syntax? I'd be happy to get some docs, websites or examples too.
The {% _________ %} are template tags. They are used to interpolate a tag into the space. Examples include extend, include, and load to name but a few. They often extend, insert, or give some sort logical functionality in some way (if conditions or loops, etc).
The {{ ___________ }} syntax is for template variables. This is used to interpolate a variable declared either as one of the built-in options or your own which you have created from any number of methods (models, view context, etc).
The Django docs are pretty thorough with use cases of all these. Another website which shortlists these to make them readily understandable is https://www.djangotemplatetagsandfilters.com/
It doesn't mean anything in html itself, it means something in Django template language. For example:
{{ choice.choice_text }}
will substitute value of that variable during template rendering.
The other one {% and %} is used for template processing, for example to indicate to template processor that some task needs to be completed. Good example is:
{% if error %}
{{ error }}
{% endif %}
That means that the variable error will be displayed (rendered) only if it exists, or to be more precise if it has some value.
The ones you are referring are jinja codes. They are very essential to work with Django and also they easy to understand when you have general understanding about python and django. You can find the documentation about jinga in this URL Jinja2 Documentation
I followed instructions in simmilar thread like: How do you index on a jinja template?
but my html template is not working and whole django project is not responding due to this.
Error that I'm getting:
Error during template rendering.
Could not parse the remainder: '[loop.index0]' from 'songs_titles[loop.index0]'
My code looks like this:
{% if converted_files_urls %}
<p>Titles: {{ songs_titles }}</p>
{% for n in converted_files_urls %}
<a href="{{ n }}" download>Download: {{ songs_titles[loop.index0] }}</a>
<br/>
{% endfor %}
{% endif %}
and the {{ songs_titles }} renders as list, so at least till here it works ok.
What am I doing wrong?
Actually you are looking for Jinja, that will not work on django.
In django template tag you should use forloop.counter0 and list indexing looks like
{{songs_titles.1}}
Need to set count in variable and then use it, for setting variable you could use -
{% with index=forloop.counter0 %}
{{ songs_titles.index}}
{% endwith %}
Still If you have any doubts you can comment it.
I finally resolved this by creating a custom template tag like here:
https://djangosnippets.org/snippets/2740/
But to be honest it sucks that that's the simplest working solution for now :/
In my template I have
<p>{% for dict_item in MySQL_Dict %}
{% for key, value in dict_item.items() %}
{{value}}
{% endfor %}
{% endfor %}</p>
Which outputs 43.8934276 -103.3690243 47.052060 -91.639868 How do I keep values i.e. the coordinates together AND have them separated by a comma? Is this possible?
The easiest way is to format it on back-end and pass it the jinja in the way you want. In fact its better to put complex logic on the back-end not the front-end performs better and in jinja's case you don't have to pass in python methods so it's cleaner... other templating frameworks like tornados include all of pythons base functions so you don't have to pass them in like the example below. Another way to do it is to pass the str.join, len, and range method to jinja e.x join=str.join, len=len, range=range then... and I'm guessing MySQL_Dict is a 2d array, hence the double for loop
<p>
{% for dict_item in MySQL_Dict %} // dict_item == [{}, {}, ...]
{% for i in range(len(dict_item)) %} // dict_item[i] == {some object}
{{",".join(dict_item[i]["latitude"], dict_item[i]["longitude"])}}
{% endfor %}
{% endfor %}
</p>
I'm building a website using Flask with its jinja2 templating engine and I'm dynamically building the menu (as described here):
{%
set navigation_bar = [
('/', 'index', 'Home'),
('/aboutus/', 'aboutus', 'About Us'),
('/faq/', 'faq', 'FAQ')
]
%}
{% set active_page = active_page|default('index') -%}
<ul>
{% for href, id, title in navigation_bar %}
<li{% if id == active_page %} class="active"{% endif %}>
{{ title|e }}
</li>
{% endfor %}
</ul>
Now if a user is logged in I want to show some additional things. So at runtime I want to add items to the navigation_bar variable. I tried something like this:
{% if g.user.is_authenticated() %}
{% navigation_bar.append(('/someotherpage', 'someotherpage', 'SomeOtherPage')) -%}
{% endif %}
But unfortunately this results in the following error: TemplateSyntaxError: Encountered unknown tag 'navigation_bar'. Jinja was looking for the following tags: 'endblock'. The innermost block that needs to be closed is 'block'.
So: does anybody know how I can add additional items to a jinja2 variable at runtime? All tips are welcome!
[bonus question]
I was also wondering, what does the - do at the end of {% set active_page = active_page|default('index') -%}?
The error occurs because Jinja can't identify block. Each Jinja block should start from block name. do block from do extension meets your needs. To use it you should add
do extension to jinja extensions. You can do this like so:
app.jinja_env.add_extension('jinja2.ext.do')
And then you can use do extension. Your example should looks like this:
{% if g.user.is_authenticated() %}
{% do navigation_bar.append(('/someotherpage', 'someotherpage', 'SomeOtherPage')) %}
{% endif %}
Here's another simple example.
You will find answer to your bonus question here. In short - removes whitespaces from start or end of block (this depends on where it is located).
To complete the answer of Slava Bacherikov, if you don't have the Jinja "do extension", you can use the tag set:
{% if g.user.is_authenticated() %}
{# use a dummy variable name, we juste need the side-effect of method call #}
{% set _z = navigation_bar.append(('/someotherpage', 'someotherpage', 'SomeOtherPage')) %}
{% endif %}