I have URLs like http://example.com/depict?smiles=CO&width=200&height=200 (and with several other optional arguments)
My urls.py contains:
urlpatterns = patterns('',
(r'^$', 'cansmi.index'),
(r'^cansmi$', 'cansmi.cansmi'),
url(r'^depict$', cyclops.django.depict, name="cyclops-depict"),
I can go to that URL and get the 200x200 PNG that was constructed, so I know that part works.
In my template from the "cansmi.cansmi" response I want to construct a URL for the named template "cyclops-depict" given some query parameters. I thought I could do
{% url cyclops-depict smiles=input_smiles width=200 height=200 %}
where "input_smiles" is an input to the template via a form submission. In this case it's the string "CO" and I thought it would create a URL like the one at top.
This template fails with a TemplateSyntaxError:
Caught an exception while rendering: Reverse for 'cyclops-depict' with arguments '()' and keyword arguments '{'smiles': u'CO', 'height': 200, 'width': 200}' not found.
This is a rather common error message both here on StackOverflow and elsewhere. In every case I found, people were using them with parameters in the URL path regexp, which is not the case I have where the parameters go into the query.
That means I'm doing it wrong. How do I do it right? That is, I want to construct the full URL, including path and query parameters, using something in the template.
For reference,
% python manage.py shell
Python 2.6.1 (r261:67515, Feb 11 2010, 00:51:29)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from django.core.urlresolvers import reverse
>>> reverse("cyclops-depict", kwargs=dict())
'/depict'
>>> reverse("cyclops-depict", kwargs=dict(smiles="CO"))
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/Library/Python/2.6/site-packages/django/core/urlresolvers.py", line 356, in reverse
*args, **kwargs)))
File "/Library/Python/2.6/site-packages/django/core/urlresolvers.py", line 302, in reverse
"arguments '%s' not found." % (lookup_view_s, args, kwargs))
NoReverseMatch: Reverse for 'cyclops-depict' with arguments '()' and keyword arguments '{'smiles': 'CO'}' not found.
Building an url with query string by string concatenation as suggested by some answers is as bad idea as building SQL queries by string concatenation. It is complicated, unelegant and especially dangerous with a user provided (untrusted) input. Unfortunately Django does not offer an easy possibility to pass query parameters to the reverse function.
Python standard urllib however provides the desired query string encoding functionality.
In my application I've created a helper function:
def url_with_querystring(path, **kwargs):
return path + '?' + urllib.urlencode(kwargs) # for Python 3, use urllib.parse.urlencode instead
Then I call it in the view as follows:
quick_add_order_url = url_with_querystring(reverse(order_add),
responsible=employee.id, scheduled_for=datetime.date.today(),
subject='hello world!')
# http://localhost/myapp/order/add/?responsible=5&
# scheduled_for=2011-03-17&subject=hello+world%21
Please note the proper encoding of special characters like space and exclamation mark!
Your regular expresion has no place holders (that's why you are getting NoReverseMatch):
url(r'^depict$', cyclops.django.depict, name="cyclops-depict"),
You could do it like this:
{% url cyclops-depict %}?smiles=CO&width=200&height=200
URLconf search does not include GET or POST parameters
Or if you wish to use {% url %} tag you should restructure your url pattern to something like
r'^depict/(?P<width>\d+)/(?P<height>\d+)/(?P<smiles>\w+)$'
then you could do something like
{% url cyclops-depict 200 200 "CO" %}
Follow-up:
Simple example for custom tag:
from django.core.urlresolvers import reverse
from django import template
register = template.Library()
#register.tag(name="myurl")
def myurl(parser, token):
tokens = token.split_contents()
return MyUrlNode(tokens[1:])
class MyUrlNode(template.Node):
def __init__(self, tokens):
self.tokens = tokens
def render(self, context):
url = reverse('cyclops-depict')
qs = '&'.join([t for t in self.tokens])
return '?'.join((url,qs))
You could use this tag in your templates like so:
{% myurl width=200 height=200 name=SomeName %}
and hopefully it should output something like
/depict?width=200&height=200&name=SomeName
I recommend to use builtin django's QueryDict. It also handles lists properly. End automatically escapes some special characters (like =, ?, /, '#'):
from django.http import QueryDict
from django.core.urlresolvers import reverse
q = QueryDict('', mutable=True)
q['some_key'] = 'some_value'
q.setlist('some_list', [1,2,3])
'%s?%s' % (reverse('some_view_name'), q.urlencode())
# '/some_url/?some_list=1&some_list=2&some_list=3&some_key=some_value'
q.appendlist('some_list', 4)
q['value_with_special_chars'] = 'hello=w#rld?'
'%s?%s' % (reverse('some_view_name'), q.urlencode())
# '/some_url/?value_with_special_chars=hello%3Dw%23rld%3F&some_list=1&some_list=2&some_list=3&some_list=4&some_key=some_value'
To use this in templates you will need to create custom template tag
Working variation of previous answers and my experience with dealing this stuff.
from django.urls import reverse
from django.utils.http import urlencode
def build_url(*args, **kwargs):
params = kwargs.pop('params', {})
url = reverse(*args, **kwargs)
if params:
url += '?' + urlencode(params)
return url
How to use:
>>> build_url('products-detail', kwargs={'pk': 1}, params={'category_id': 2})
'/api/v1/shop/products/1/?category_id=2'
The answer that used urllib is indeed good, however while it was trying to avoid strings concatenation, it used it in path + '?' + urllib.urlencode(kwargs). I believe this may create issues when the path has already some query parmas.
A modified function would look like:
def url_with_querystring(url, **kwargs):
url_parts = list(urlparse.urlparse(url))
query = dict(urlparse.parse_qsl(url_parts[4]))
query.update(kwargs)
url_parts[4] = urllib.urlencode(query)
return urlparse.urlunparse(url_parts)
Neither of the original answers addresses the related issue resolving URLs in view code. For future searchers, if you are trying to do this, use kwargs, something like:
reverse('myviewname', kwargs={'pk': value})
Related
I have a django-cms site, that uses i18n_patterns in urls.py. This works, urls are built like /lang/here-starts-the-normal/etc/.
Now, I would like to have urls like this: /prefix-lang/here-starts.... As there will be a couple of country specific domains, this wille be like /ch-de/here-... for Switzerland/.ch domain, /us-en/here-starts.... for the states, and some more. So, when the url would be /ch-de/..., the LANGUAGE would still be de. Hope this is clear?
As the content is filled with existing LANGUAGES=(('de', 'DE'), ('en', 'EN'), ...), I cannot change LANGUAGES for every domain - no content would be found in the cms, modeltranslation, only to mention those two.
How can I prefix the language slug in i18n_patterns? Is it possible at all?
I think a way without hacking Django too much would be to use URL rewrite facility provided by the webserver you run, for example, for mod_wsgi you can use mod_rewrite, similar facility exists also for uWSGI.
You may need to also post-process the output from Django to make sure that any links are also correctly re-written to follow the new schema. Not the cleanest approach but seems doable.
Working example, though the country/language order is reversed (en-ch instead of ch-en), to have it as django expects it when trying to find a language (ie, setting language to "en-ch", it will find "en", if available).
This solution involves a modified LocaleMiddleware, i18n_patterns, LocaleRegexResolver. It supports no country, or a 2 char country code, setup with settings.SITE_COUNTRY. It works by changing urls to a lang-country mode, but the found language code in middleware will still be language only, 2 chars, and work perfectly with existing LANGUAGES, that contain 2 chars language codes.
custom_i18n_patterns.py - this just uses our new resolver, see below
from django.conf import settings
from ceco.resolvers import CountryLocaleRegexURLResolver
def country_i18n_patterns(*urls, **kwargs):
"""
Adds the language code prefix to every URL pattern within this
function. This may only be used in the root URLconf, not in an included
URLconf.
"""
if not settings.USE_I18N:
return list(urls)
prefix_default_language = kwargs.pop('prefix_default_language', True)
assert not kwargs, 'Unexpected kwargs for i18n_patterns(): %s' % kwargs
return [CountryLocaleRegexURLResolver(list(urls), prefix_default_language=prefix_default_language)]
resolvers.py
import re
from django.conf import settings
from django.urls import LocaleRegexURLResolver
from modeltranslation.utils import get_language
class CountryLocaleRegexURLResolver(LocaleRegexURLResolver):
"""
A URL resolver that always matches the active language code as URL prefix.
extended, to support custom country postfixes as well.
"""
#property
def regex(self):
language_code = get_language() or settings.LANGUAGE_CODE
if language_code not in self._regex_dict:
if language_code == settings.LANGUAGE_CODE and not self.prefix_default_language:
regex_string = ''
else:
# start country changes
country_postfix = ''
if getattr(settings, 'SITE_COUNTRY', None):
country_postfix = '-{}'.format(settings.SITE_COUNTRY)
regex_string = '^%s%s/' % (language_code, country_postfix)
# end country changes
self._regex_dict[language_code] = re.compile(regex_string, re.UNICODE)
return self._regex_dict[language_code]
middleware.py - only very few lines changed, but had to replace the complete process_response.
from django.middleware.locale import LocaleMiddleware
from django.conf import settings
from django.conf.urls.i18n import is_language_prefix_patterns_used
from django.http import HttpResponseRedirect
from django.urls import get_script_prefix, is_valid_path
from django.utils import translation
from django.utils.cache import patch_vary_headers
class CountryLocaleMiddleware(LocaleMiddleware):
"""
This is a very simple middleware that parses a request
and decides what translation object to install in the current
thread context. This allows pages to be dynamically
translated to the language the user desires (if the language
is available, of course).
"""
response_redirect_class = HttpResponseRedirect
def process_response(self, request, response):
language = translation.get_language()
language_from_path = translation.get_language_from_path(request.path_info)
urlconf = getattr(request, 'urlconf', settings.ROOT_URLCONF)
i18n_patterns_used, prefixed_default_language = is_language_prefix_patterns_used(urlconf)
if (response.status_code == 404 and not language_from_path and
i18n_patterns_used and prefixed_default_language):
# Maybe the language code is missing in the URL? Try adding the
# language prefix and redirecting to that URL.
# start country changes
language_country = language
if getattr(settings, 'SITE_COUNTRY', None):
language_country = '{}-{}'.format(language, settings.SITE_COUNTRY)
language_path = '/%s%s' % (language_country, request.path_info)
# end country changes!
path_valid = is_valid_path(language_path, urlconf)
path_needs_slash = (
not path_valid and (
settings.APPEND_SLASH and not language_path.endswith('/') and
is_valid_path('%s/' % language_path, urlconf)
)
)
if path_valid or path_needs_slash:
script_prefix = get_script_prefix()
# Insert language after the script prefix and before the
# rest of the URL
language_url = request.get_full_path(force_append_slash=path_needs_slash).replace(
script_prefix,
'%s%s/' % (script_prefix, language_country),
1
)
return self.response_redirect_class(language_url)
if not (i18n_patterns_used and language_from_path):
patch_vary_headers(response, ('Accept-Language',))
if 'Content-Language' not in response:
response['Content-Language'] = language
return response
There is a filter that adds to form django_crispy_form functionality. All arguments passing as string divided by ",".
# -*- coding: utf-8 -*-
from crispy_forms.helper import FormHelper
from crispy_forms.layout import Submit
from django.core.urlresolvers import reverse
from django.template import Library
register = Library()
#args=[url_name, submit_button_text, optional_<pk>]
#register.filter
def with_submit(form, args):
sargs = args.split(',')
action, name = sargs[:2]
if len(sargs) > 2:
args = sargs[2:]
else:
args = None
helper = FormHelper()
helper.form_method = 'POST'
if args:
#there exception throwed every time if len of args > 2
helper.form_action = reverse(action, int(args[0]))
else:
helper.form_action = reverse(action)
helper.add_input(Submit(action, name, css_class='btn btn-primary'))
form.helper = helper
return form
When I use this filter without third optional argument - it works fine, but when I add third <pk> argument - it crashes and says:
The included URLconf '1' does not appear to have any patterns in it. If you see valid patterns in the file then the issue is probably caused by a circular import.
And I don't know where I should find circular import.
The signature of the reverse method is:
reverse(viewname, urlconf=None, args=None, kwargs=None, current_app=None)
So, your second argument of int(args[0]) is being passed in as urlconf, which is leading to the exception. You need to use
reverse(action, args=int(args[0]))
Whenever you write template tags or filters, you have to be very careful that you code is as simple and as robust as possible. Custom tags and filters are the most difficult parts of a django application to debug.
Consider this line:
action, name = sargs[:2]
This line will raise ValueError if there aren't exactly two items in sargs[:2]. You should do a check first before executing this statement.
I have a search page that takes a variety of parameters. I want to create a new URL by just altering one parameter in the query. Is there an easy way to do this - something like:
# example request url
http://example.com/search?q=foo&option=bar&option2=baz&change=before
# ideal template code
{% url_with change 'after' %}
# resulting url
http://example.com/search?q=foo&option=bar&option2=baz&change=after
So this would take the request url, alter one query parameter and then return the new url. Similar to what can be achieved in Perl's Catalyst using $c->uri_with({change => 'after'}).
Or is there a better way?
[UPDATED: removed references to pagination]
I did this simple tag which doesn't require any extra libraries:
#register.simple_tag
def url_replace(request, field, value):
dict_ = request.GET.copy()
dict_[field] = value
return dict_.urlencode()
Use as:
<a href="?{% url_replace request 'param' value %}">
It wil add 'param' to your url GET string if it's not there, or replace it with the new value if it's already there.
You also need the RequestContext request instance to be provided to your template from your view. More info here:
http://lincolnloop.com/blog/2008/may/10/getting-requestcontext-your-templates/
So, write a template tag around this:
from urlparse import urlparse, urlunparse
from django.http import QueryDict
def replace_query_param(url, attr, val):
(scheme, netloc, path, params, query, fragment) = urlparse(url)
query_dict = QueryDict(query).copy()
query_dict[attr] = val
query = query_dict.urlencode()
return urlunparse((scheme, netloc, path, params, query, fragment))
For a more comprehensive solution, use Zachary Voase's URLObject 2, which is very nicely done.
Note:
The urlparse module is renamed to urllib.parse in Python 3.
I improved mpaf's solution, to get request directly from tag.
#register.simple_tag(takes_context = True)
def url_replace(context, field, value):
dict_ = context['request'].GET.copy()
dict_[field] = value
return dict_.urlencode()
This worked pretty well for me. Allows you to set any number of parameters in the URL. Works nice for a pager, while keeping the rest of the query string.
from django import template
from urlobject import URLObject
register = template.Library()
#register.simple_tag(takes_context=True)
def url_set_param(context, **kwargs):
url = URLObject(context.request.get_full_path())
path = url.path
query = url.query
for k, v in kwargs.items():
query = query.set_param(k, v)
return '{}?{}'.format(path, query)
Then in the template:
<a href="{% url_set_param page=last %}">
There are a number of template tags for modifying the query string djangosnippets.org:
http://djangosnippets.org/snippets/553/
http://djangosnippets.org/snippets/826/
http://djangosnippets.org/snippets/1243/
I would say those are the most promising looking. One point in all of them is that you must be using django.core.context_processors.request in your TEMPLATE_CONTEXT_PROCESSORS.
You can try https://github.com/dcramer/django-paging
In addition to the snippets mentioned by Mark Lavin, Here's a list of other implementations I could find for a Django template tag which modifies the current HTTP GET query string.
On djangosnippets.org:
#2237 Manipulate URL query strings using context variables using a template tag by JHsaunders
#2332 Querystring Builder - create urls with GET params by jibberia
my favorite: #2413 Yet another query string template tag by atms
#2428 Add GET parameters from current request by naktinis
On PyPI:
django-spurl by Jamie Matthews
django-urltags by Calloway Project/Corey Oordt
the add_query_param filter in django-rest-framework by Tom Christie
On GitHub:
update_querystring by David Gouldin
I'm using the Django Feeds Framework and it's really nice, very intuitive and easy to use. But, I think there is a problem when creating links to feeds in HTML.
For example:
<link rel="alternate" type="application/rss+xml" title="{{ feed_title }}" href="{{ url_of_feed }}" />
Link's HREF attribute can be easily found out, just use reverse()
But, what about the TITLE attribute? Where the template engine should look for this? Even more, what if the feed is build up dinamically and the title depends on parameters (like this)?
I can't come up with a solution that "seems" DRY to me... All that I can come up with is using context processors o template tags, but it gets messy when the context procesor/template tag has to find parameters to construct the Feed class, and writing this I realize I don't even know how to create a Feed instance myself within the view.
If I put all this logic in the view, it would not be just one view. Also, the value for TITLE would be in the view AND in the feed.
Just a guess (as I have not used feeds yet in my django app), but you could add a special template_context for your feed with your feed object and use it in your base.html.
I'm not fully satisfied with this solution, it may break feeds using Request and depends on a magic method. There it goes:
#coding:utf-8
# Author: Armando Pérez Marqués <mandx#rbol.org>
# Purpose: Django TemplateTag to output feed links in templates in a DRY way
# Created: 05/07/2010
import re
from django import template
from django.conf import settings
from django.contrib.syndication.views import Feed
from django.core.urlresolvers import reverse, resolve, NoReverseMatch
from django.template import Node
from django.template import TemplateSyntaxError
from django.utils.encoding import smart_str
from django.utils.html import escape as html_escape
from django.utils.safestring import mark_safe
register = template.Library()
kwarg_re = re.compile(r"(?:(\w+)=)?(.+)")
class FeedInfoNode(Node):
def __init__(self, view_name, args, kwargs, asvar):
self.view_name = view_name
self.args = args
self.kwargs = kwargs
self.asvar = asvar
def render(self, context):
args = [arg.resolve(context) for arg in self.args]
kwargs = dict([(smart_str(k,'ascii'), v.resolve(context))
for k, v in self.kwargs.items()])
# Try to look up the URL twice: once given the view name, and again
# relative to what we guess is the "main" app. If they both fail,
# re-raise the NoReverseMatch unless we're using the
# {% feed_info ... as var %} construct in which cause return nothing.
url = ''
try:
url = reverse(self.view_name, args=args, kwargs=kwargs, current_app=context.current_app)
except NoReverseMatch, e:
if settings.SETTINGS_MODULE:
project_name = settings.SETTINGS_MODULE.split('.')[0]
try:
url = reverse(project_name + '.' + self.view_name,
args=args, kwargs=kwargs, current_app=context.current_app)
except NoReverseMatch:
if self.asvar is None:
# Re-raise the original exception, not the one with
# the path relative to the project. This makes a
# better error message.
raise e
else:
if self.asvar is None:
raise e
if 'request' in context:
request = context['request']
else:
request = None
feed_instance, feed_args, feed_kwargs = resolve(url)
if not isinstance(feed_instance, Feed):
raise NoReverseMatch, \
'feed_info can only reverse class-based feeds'
feed_obj = feed_instance.get_object(request, *feed_args, **feed_kwargs)
feed_data = {
'url': url,
'obj': feed_instance,
'args': feed_args,
'kwargs': feed_kwargs,
#'title': html_escape(feed_instance.__get_dynamic_attr('title', obj)),
'title': html_escape(
feed_instance._Feed__get_dynamic_attr('title', feed_obj)
),
'type': feed_instance.feed_type.mime_type,
}
if self.asvar:
context[self.asvar] = feed_data
return ''
else:
return mark_safe(
'<link rel="alternate" type="%(type)s" title="%(title)s" href="%(url)s" />' \
% feed_data
)
def feed_info(parser, token):
"""
Returns an mapping containing populated info about the reversed feed
Works exactly as the url tag, but the mapping is not returned, instead
a variable is always set in the context.
This is a way to define links that aren't tied to a particular URL
configuration::
{% feed_info path.to.some_feed_view_class arg1 arg2 as feed_info_var %}
or
{% feed_info path.to.some_feed_view_class name1=value1 name2=value2 as feed_info_var %}
"""
bits = token.split_contents()
if len(bits) < 2:
raise TemplateSyntaxError("'%s' takes at least one argument"
" (path to a feed view)" % bits[0])
viewname = bits[1]
args = []
kwargs = {}
asvar = None
bits = bits[2:]
if len(bits) >= 2 and bits[-2] == 'as':
asvar = bits[-1]
bits = bits[:-2]
# Backwards compatibility: check for the old comma separated format
# {% url urlname arg1,arg2 %}
# Initial check - that the first space separated bit has a comma in it
if bits and ',' in bits[0]:
check_old_format = True
# In order to *really* be old format, there must be a comma
# in *every* space separated bit, except the last.
for bit in bits[1:-1]:
if ',' not in bit:
# No comma in this bit. Either the comma we found
# in bit 1 was a false positive (e.g., comma in a string),
# or there is a syntax problem with missing commas
check_old_format = False
break
else:
# No comma found - must be new format.
check_old_format = False
if check_old_format:
# Confirm that this is old format by trying to parse the first
# argument. An exception will be raised if the comma is
# unexpected (i.e. outside of a static string).
match = kwarg_re.match(bits[0])
if match:
value = match.groups()[1]
try:
parser.compile_filter(value)
except TemplateSyntaxError:
bits = ''.join(bits).split(',')
# Now all the bits are parsed into new format,
# process them as template vars
if len(bits):
for bit in bits:
match = kwarg_re.match(bit)
if not match:
raise TemplateSyntaxError("Malformed arguments to url tag")
name, value = match.groups()
if name:
kwargs[name] = parser.compile_filter(value)
else:
args.append(parser.compile_filter(value))
return FeedInfoNode(viewname, args, kwargs, asvar)
feed_info = register.tag(feed_info)
I'm starting with the code of the {% url %} template tag, and then, after obtaining the feed's URL, use resolve() to get the Feed subclass instance, and then get the needed attributes.
Caveats
Requires Django 1.2 Class Feeds, don't know exactly how to do this with the old way of feeds.
If the feed class uses the request object, the request context processor must be configured, since None is passed if it isn't present in the context.
There's an oddity with Feed.__get_dynamic_attr(). The Feed subclass instance doesn't have this method; instead, it appears with another name. Don't know how to figure the name out at runtime...
I am trying to incorporate django-schedule into my project. Django-schedule's source is here. I don't like the urls, because they all capture a slug. My project will only allow one calendar per user, so it doesn't make sense to capture the slug. So, I wrapped the django-schedule views like this (look up the slug using the current user, and pass it to django-schedule's views):
from schedule.views import calendar_by_periods
from schedule.models import Calendar
from schedule.periods import Month
def cal_by_periods_wrapper(view):
def new_view(request, *args, **kwargs):
kwargs['calendar_slug'] = Calendar.objects.get_calendars_for_object(obj=request.user, distinction="owner")[0].slug
return view(request, *args, **kwargs)
return new_view
And here is the relevant section from urls.py:
urlpatterns = patterns('',
url(r'^$',
cal_by_periods_wrapper(calendar_by_periods),
name = "month_calendar",
kwargs={'periods': [Month], 'template_name': 'schedule/calendar_month.html'}),
This works fine until it hits one of the template tags included with django-schedule, prev_url:
#register.simple_tag
def prev_url(target, slug, period):
return '%s%s' % (
reverse(target, kwargs=dict(calendar_slug=slug)),
querystring_for_date(period.prev().start))
This function raises:
TemplateSyntaxError at /teacher/calendar/
Caught an exception while rendering: Reverse for 'month_calendar' with arguments
'()' and keyword arguments '{'calendar_slug': u'asdf'}' not found.
How can I wrap this view and still make the reverse call work?
This has nothing to do with wrapping the function. It's just that you no longer have a URL with the name 'month_calendar' which takes a 'calendar_slug' argument. Either define one in your urlconf, or edit the templatetag.
Edit after comment Yes but the 'reverse' call is still passing a slug argument, and there's no 'month_calendar' url which takes one, so the reverse match fails.