def map_postcodes_to_constituencies(postcode_file, constituencies, ids):
with open(postcode_file) as f:
postcode_constituencies = {}
unknowns = []
last_constituencies = [constituencies.keys()[0]]*5
n = 0
for postcode,point in postcodes_to_points(f):
constituency = None
n += 1
# The postcodes are in alphabetical order - so it's relatively
# likely that this postcode will be in the same constituency as one
# of the last five postcodes. Check those first.
for guess in reversed(last_constituencies):
if constituencies[guess].contains(point):
last_constituencies.remove(guess)
constituency = guess
# If that didn't work, we should loop through every constituency.
if postcode not in postcode_constituencies:
for possible_constituency in constituencies.keys():
if constituencies[possible_constituency].contains(point):
constituency = possible_constituency
break
# Sometimes we don't get a result, usually because of postcodes on
# Scottish islands which fall outside the constituency boundaries
# we're using. Make a best guess.
if constituency is None:
constituency = guess_constituency(postcode, point, constituencies)
if constituency not in ids:
ids[constituency] = waw_app.models.Constituency.objects.filter(
name__exact=constituency)[0]
new_postcode = waw_app.models.Postcode.objects.create(
postcode=postcode, constituency=ids[constituency])
new_postcode.save()
last_constituencies.append(constituency)
def map_postcodes_to_constituencies(postcode_file, constituencies, verbose=False):
with open(postcode_file) as f:
postcode_constituencies = {}
unknowns = []
last_constituencies = [constituencies.keys()[0]] * 5
n = 0
for postcode, point in postcodes_to_points(f):
n += 1
# The postcodes are in alphabetical order - so it's relatively
# likely that this postcode will be in the same constituency as one
# of the last five postcodes. Check those first.
for guess in last_constituencies:
if constituencies[guess].contains(point):
last_constituencies.remove(guess)
postcode_constituencies[postcode] = guess
last_constituencies.append(guess)
# If that didn't work, we should loop through every constituency.
if postcode not in postcode_constituencies:
for constituency in constituencies.keys():
if constituencies[constituency].contains(point):
postcode_constituencies[postcode] = constituency
last_constituencies.append(constituency)
break
# Sometimes we don't get a result, usually because of postcodes on
# Scottish islands which fall outside the constituency boundaries
# we're using. Collect those postcodes into a list of unknowns,
# for further processing (eg. a lookup on http://parliament.uk or a
# best guess by distance).
if postcode not in postcode_constituencies:
unknowns.append((postcode, point))
if verbose and 0 == (n % 1000):
print("%d postcodes processed" % n)
return (postcode_constituencies, unknowns)