Sorry!
Just found it : Modules
Extract :
In addition, this module contains some utility functions:
from anvil import *
print "Our URL hash is: " + repr(get_url_hash())
get_url_hash() gets the decoded hash (the part after the '#' character) of the URL used to open this app.
If the first character of the hash is a question mark (eg https://myapp.anvilapp.net/#?a=foo&b=bar), it will be interpreted as query-string-type parameters and returned as a dictionary (eg {'a': 'foo', 'b': 'bar'}).