Develop Reference

Why urls order is important in django for different named urls?

I have two urls in my urls.py file
url('to_quotation/$', views.to_quotation, name='to_quotation'),
url('turn_into_quotation/$', views.turn_into_quotation, name='turn_into_quotation'),
and i have two view for them in views.py. When i make an ajax call to 'turn_into_quotation' url, 'to_quotation' view works. But if i changed my urls.py as:
url('turn_into_quotation/$', views.turn_into_quotation, name='turn_into_quotation'),
url('to_quotation/$', views.to_quotation, name='to_quotation'),
it works properly.
What is the reason for that?

You are missing the ^ at the beginning of the regex. Change it to:
url(r'^to_quotation/$', views.to_quotation, name='to_quotation'),
url(r'^turn_into_quotation/$', views.turn_into_quotation, name='turn_into_quotation'),
Without the ^, to_quotation/$ matches to_quotation/ and also turn_into_quotation/. In that case, the order matters, because Django will use the first URL pattern that matches.
If you're using a recent version of Django, you could use path() instead, and avoid regex gotchas.
path('to_quotation/', views.to_quotation, name='to_quotation'),
path('turn_into_quotation/', views.turn_into_quotation, name='turn_into_quotation'),

#Alasdair's answer is amazing~ I'd like to attach more infomations:
Django use regex-like syntax to match it and split url's argument:
^to-quotation/<id: int>/$`
It will: 1. try to match the url, 2. try to split its argument from url, and here it split int-value to id.
So it is easy to know, in the url's settings, it is important to hold each sub-url cannot match another.

Something's Wrong When I Try to Register on my Website [duplicate]

I have some code and when it executes, it throws a NoReverseMatch, saying:
NoReverseMatch at /my_url/ Reverse for 'my_url_name' with arguments '()' and keyword arguments '{}' not found. n pattern(s) tried: []
What does this mean, and what can I do about it?

The NoReverseMatch error is saying that Django cannot find a matching url pattern for the url you've provided in any of your installed app's urls.
The NoReverseMatch exception is raised by django.core.urlresolvers when a matching URL in your URLconf cannot be identified based on the parameters supplied.
To start debugging it, you need to start by disecting the error message given to you.
NoReverseMatch at /my_url/
This is the url that is currently being rendered, it is this url that your application is currently trying to access but it contains a url that cannot be matched
Reverse for 'my_url_name'
This is the name of the url that it cannot find
with arguments '()' and
These are the non-keyword arguments its providing to the url
keyword arguments '{}' not found.
These are the keyword arguments its providing to the url
n pattern(s) tried: []
These are the patterns that it was able to find in your urls.py files that it tried to match against
Start by locating the code in your source relevant to the url that is currently being rendered - the url, the view, and any templates involved. In most cases, this will be the part of the code you're currently developing.
Once you've done this, read through the code in the order that django would be following until you reach the line of code that is trying to construct a url for your my_url_name. Again, this is probably in a place you've recently changed.
Now that you've discovered where the error is occuring, use the other parts of the error message to work out the issue.
The url name
Are there any typos?
Have you provided the url you're trying to access the given name?
If you have set app_name in the app's urls.py (e.g. app_name = 'my_app') or if you included the app with a namespace (e.g. include('myapp.urls', namespace='myapp'), then you need to include the namespace when reversing, e.g. {% url 'myapp:my_url_name' %} or reverse('myapp:my_url_name').
Arguments and Keyword Arguments
The arguments and keyword arguments are used to match against any capture groups that are present within the given url which can be identified by the surrounding () brackets in the url pattern.
Assuming the url you're matching requires additional arguments, take a look in the error message and first take a look if the value for the given arguments look to be correct.
If they aren't correct:
The value is missing or an empty string
This generally means that the value you're passing in doesn't contain the value you expect it to be. Take a look where you assign the value for it, set breakpoints, and you'll need to figure out why this value doesn't get passed through correctly.
The keyword argument has a typo
Correct this either in the url pattern, or in the url you're constructing.
If they are correct:
Debug the regex
You can use a website such as regexr to quickly test whether your pattern matches the url you think you're creating, Copy the url pattern into the regex field at the top, and then use the text area to include any urls that you think it should match against.
Common Mistakes:
Matching against the . wild card character or any other regex characters
Remember to escape the specific characters with a \ prefix
Only matching against lower/upper case characters
Try using either a-Z or \w instead of a-z or A-Z
Check that pattern you're matching is included within the patterns tried
If it isn't here then its possible that you have forgotten to include your app within the INSTALLED_APPS setting (or the ordering of the apps within INSTALLED_APPS may need looking at)
Django Version
In Django 1.10, the ability to reverse a url by its python path was removed. The named path should be used instead.
If you're still unable to track down the problem, then feel free to ask a new question that includes what you've tried, what you've researched (You can link to this question), and then include the relevant code to the issue - the url that you're matching, any relevant url patterns, the part of the error message that shows what django tried to match, and possibly the INSTALLED_APPS setting if applicable.

A very common error is when you get with arguments ('',). This is caused by something like this:
{% url 'view-name' does_not_exist %}
As does_not_exist doesn't exist, django evaluates it to the empty string, causing this error message.
If you install django-fastdev you will instead get a nice crash saying does_not_exist doesn't exist which is the real problem.

With django-extensions you can make sure your route in the list of routes:
./manage.py show_urls | grep path_or_name
If the route is missing you probably have not imported the application.

It may be that it's not loading the template you expect. I added a new class that inherited from UpdateView - I thought it would automatically pick the template from what I named my class, but it actually loaded it based on the model property on the class, which resulted in another (wrong) template being loaded. Once I explicitly set template_name for the new class, it worked fine.

The arguments part is typically an object from your models. Remember to add it to your context in the view. Otherwise a reference to the object in the template will be empty and therefore not match a url with an object_id.

Watch out for different arguments passing between reverse() and redirect() for example:
url(r"^some_app/(?P<some_id>\d+)/$", some_view_function, name="some_view")
will work with:
reverse("some_view", kwargs={"some_id": my_id})
and:
redirect("some_view", some_id=my_id)
but not with:
reverse("some_view", some_id=my_id)
and:
redirect("some_view", kwargs={"some_id": my_id})

Django reverse error [duplicate]

I have some code and when it executes, it throws a NoReverseMatch, saying:
NoReverseMatch at /my_url/ Reverse for 'my_url_name' with arguments '()' and keyword arguments '{}' not found. n pattern(s) tried: []
What does this mean, and what can I do about it?

The NoReverseMatch error is saying that Django cannot find a matching url pattern for the url you've provided in any of your installed app's urls.
The NoReverseMatch exception is raised by django.core.urlresolvers when a matching URL in your URLconf cannot be identified based on the parameters supplied.
To start debugging it, you need to start by disecting the error message given to you.
NoReverseMatch at /my_url/
This is the url that is currently being rendered, it is this url that your application is currently trying to access but it contains a url that cannot be matched
Reverse for 'my_url_name'
This is the name of the url that it cannot find
with arguments '()' and
These are the non-keyword arguments its providing to the url
keyword arguments '{}' not found.
These are the keyword arguments its providing to the url
n pattern(s) tried: []
These are the patterns that it was able to find in your urls.py files that it tried to match against
Start by locating the code in your source relevant to the url that is currently being rendered - the url, the view, and any templates involved. In most cases, this will be the part of the code you're currently developing.
Once you've done this, read through the code in the order that django would be following until you reach the line of code that is trying to construct a url for your my_url_name. Again, this is probably in a place you've recently changed.
Now that you've discovered where the error is occuring, use the other parts of the error message to work out the issue.
The url name
Are there any typos?
Have you provided the url you're trying to access the given name?
If you have set app_name in the app's urls.py (e.g. app_name = 'my_app') or if you included the app with a namespace (e.g. include('myapp.urls', namespace='myapp'), then you need to include the namespace when reversing, e.g. {% url 'myapp:my_url_name' %} or reverse('myapp:my_url_name').
Arguments and Keyword Arguments
The arguments and keyword arguments are used to match against any capture groups that are present within the given url which can be identified by the surrounding () brackets in the url pattern.
Assuming the url you're matching requires additional arguments, take a look in the error message and first take a look if the value for the given arguments look to be correct.
If they aren't correct:
The value is missing or an empty string
This generally means that the value you're passing in doesn't contain the value you expect it to be. Take a look where you assign the value for it, set breakpoints, and you'll need to figure out why this value doesn't get passed through correctly.
The keyword argument has a typo
Correct this either in the url pattern, or in the url you're constructing.
If they are correct:
Debug the regex
You can use a website such as regexr to quickly test whether your pattern matches the url you think you're creating, Copy the url pattern into the regex field at the top, and then use the text area to include any urls that you think it should match against.
Common Mistakes:
Matching against the . wild card character or any other regex characters
Remember to escape the specific characters with a \ prefix
Only matching against lower/upper case characters
Try using either a-Z or \w instead of a-z or A-Z
Check that pattern you're matching is included within the patterns tried
If it isn't here then its possible that you have forgotten to include your app within the INSTALLED_APPS setting (or the ordering of the apps within INSTALLED_APPS may need looking at)
Django Version
In Django 1.10, the ability to reverse a url by its python path was removed. The named path should be used instead.
If you're still unable to track down the problem, then feel free to ask a new question that includes what you've tried, what you've researched (You can link to this question), and then include the relevant code to the issue - the url that you're matching, any relevant url patterns, the part of the error message that shows what django tried to match, and possibly the INSTALLED_APPS setting if applicable.

A very common error is when you get with arguments ('',). This is caused by something like this:
{% url 'view-name' does_not_exist %}
As does_not_exist doesn't exist, django evaluates it to the empty string, causing this error message.
If you install django-fastdev you will instead get a nice crash saying does_not_exist doesn't exist which is the real problem.

With django-extensions you can make sure your route in the list of routes:
./manage.py show_urls | grep path_or_name
If the route is missing you probably have not imported the application.

It may be that it's not loading the template you expect. I added a new class that inherited from UpdateView - I thought it would automatically pick the template from what I named my class, but it actually loaded it based on the model property on the class, which resulted in another (wrong) template being loaded. Once I explicitly set template_name for the new class, it worked fine.

The arguments part is typically an object from your models. Remember to add it to your context in the view. Otherwise a reference to the object in the template will be empty and therefore not match a url with an object_id.

Watch out for different arguments passing between reverse() and redirect() for example:
url(r"^some_app/(?P<some_id>\d+)/$", some_view_function, name="some_view")
will work with:
reverse("some_view", kwargs={"some_id": my_id})
and:
redirect("some_view", some_id=my_id)
but not with:
reverse("some_view", some_id=my_id)
and:
redirect("some_view", kwargs={"some_id": my_id})

Django Urlconf Named Groups String Matching

I'm trying to match two strings in an url, but it's not working out likely due to my poor knowledge of regex. I want urls like the following:
testserver/username/
testserver/username/1234/
testserver/username/rewards/
Username would be passed in to the url as a kwarg. Here's what I have:
url(r'^(?P<username>[-\w]+)/$', Posts_Index, name="userposts"),
url(r'^(?P<username>[-\w]+)/photos/$', Photo_Index, name="userphotos"),
url(r'^(?P<username>[-\w]+)/rewards/$', Rewards_Index, name="userrewards"),
url(r'^(?P<username>[-\w]+)/following/$', Follower_Index, name="userfollowers"),
url(r'^(?P<username>[-\w]+)/followers/$', Following_Index, name="userfollowing"),
url(r'^(?P<username>[-\w]+)/(?P<pk>\d+)/$', SinglePost_Index, name="singlepost"),
However, only userposts will be found. If I try to query userphotos or anything below userposts, only the userposts url will be checked, which obviously leads to failure. How can I fix this issue?

From the django docs: Django runs through each URL pattern, in order, and stops at the first one that matches the requested URL.
Thus if you reverse the order of the urls it should work better.

Regular expression url Django

I would like to have one or two urls in following format in django.
e.g. /view/q/node/c/programming....
Here q, c, etc are specific get params and latter on I'll be accessing them either through js or in view.
I have tried following pattern, but it didn't work out.
r'view/(P<q>\w+)/(P<c>\w+)/(P<l>\w+)/(P<o>\w+)/$'
I know that all the get params can be accessed in view if we have ? in url. But I don't want to have ? in url.
Can anyone suggest how to achieve this? Please note that the url can be without any params also. e.g. view/.
Thanks.

You're missing the ? from your Named groups. From the Django docs:
In Python regular expressions, the syntax for named regular-expression groups is
(?P<name>pattern), where name is the name of the group and pattern is some pattern to match.
Thus, referring to your example, it should be:
r'^view/(?P<q>\w+)/(?P<c>\w+)/(?P<l>\w+)/(?P<o>\w+)/$'