difference between '^$' and '' in urls django

Question

What is the difference between the below two url patterns in django?

url(r'^$', views.indexView, name='index'),

url(r'', include('registration.urls'))

To my understanding both '^$' and '' refer to a empty string. What does '^$' and '' specify actually?

Answer 1

^$ means nothing is between the start and end ... this only matches the empty string

'' means an empty string(but does not specify anything about the beginning or end of the entire string) so when you encounter anything in the string it say well that matches 'asdasd' for example has a matching empty string at the beginning... the remaining is passed to the new url rules script (in this case everything remains)

if instead your second rule was 'a' then it would match the first a in the asdasd and pass sdasd to the new url matching rule-set

disclaimer that this is probably a gross oversimplification, but basically true

Answer 2

^$ - it specifies the start and end points of a URL string.

' ' - An empty string in URL method says, if any other URL pattern encountered that is not defined in the url pattern, then the corresponding empty string view should be called

Answer 3

In regular expressions, ^ and $ are special characters.

^ (Caret):

^ matches the start of the string.

Lets say my regex was ^a, then the regex will look for a in the start of the string:

'a'    # Matches 'a' in 'a'  
'abc'  # Matches 'a' in 'abc'
'def'  # Not match because 'a' was not at the beginning 

$ (Dollar sign):

$ matches the end of the string.

If my regex was b$, then it will match b at the end of the string:

'b'     # Matches 'b' in 'b'
'ab'    # Matches 'b' in 'ab'
'abc'   # Does not match 

Using r'^$':

Using both ^ and $ together as ^$ will match an empty line/string.

url(r'^$', views.indexView, name='index')

When Django encounters an empty string, it will go to the index page.

Using r'':

When you use r'', Django will look for an empty string anywhere in the URL, which is true for every URL.

So, if your urlpattern was like this:

url(r'', views.indexView, name='index')

All your urls will go to index page.

Answer 4

^$ means you are a matching the string between these two special characters