New API key requirement

[calebkennedyhill]

With the new api.census.gov API key requirement as of 5/12/2026, ACS5 queries no longer work.

I was able to hack my way around this by locally cloning the repo and manually appending "?key=[MY API KEY]" to the urls in core.py.

I might turn this hack into a PR with a proper fix.

[KOVALW]

The problem seems to be that the API key isn't propagated forward from query into _field_type when called from Client. Setting a dictionary params={"key": self._key} whenever session.get() is called with params being None fixes this for me locally.

[peterrrock2]

Yeah, I agree with @KOVALW there is an issue with the key not being passed properly in the _field_type function. This is a drop-in patch that I used to fix it for anyone who needs it. You need to just add this in under where you import the Census class

from census import Census

# The bit of logic below this is to fix an error caused by the Census changing its API
# requirement on 12 May 2026. The Census package did not properly pass the API key to all
# requests, so we have to patch the elements that handle that logic.
from functools import lru_cache
from census.core import Client, supported_years


def _patched_field_type(self, field, year):
    url = self.definition_url % (year, self.dataset, field)
    resp = self.session.get(url, params={"key": self._key})

    type_map = {
        "fips-for": str,
        "fips-in": str,
        "int": float,
        "long": float,
        "float": float,
        "string": str,
    }
    if resp.status_code == 200:
        try:
            predicate_type = resp.json().get("predicateType", "string")
            return type_map.get(predicate_type, str)
        except Exception:
            return str
    return str


def _patched_tables(self, year=None):
    if year is None:
        year = self.default_year
    tables_url = self.groups_url % (year, self.dataset)
    resp = self.session.get(tables_url, params={"key": self._key})
    return resp.json()["groups"]


@supported_years()
def _patched_fields(self, year=None, flat=False):
    if year is None:
        year = self.default_year

    data = {}
    fields_url = self.definitions_url % (year, self.dataset)
    resp = self.session.get(fields_url, params={"key": self._key})
    obj = resp.json()

    if flat:
        for key, elem in obj["variables"].items():
            if key in ["for", "in"]:
                continue
            data[key] = "{}: {}".format(
                elem.get("concept", ""), elem.get("label", "")
            )
    else:
        data = obj["variables"]
        data.pop("for", None)
        data.pop("in", None)
    return data


Client._field_type = lru_cache(maxsize=1024)(_patched_field_type)
Client.tables = _patched_tables
Client.fields = _patched_fields

Edit: Added patches for calls to fields and tables as well.

[antidipyramid]

Thanks for submitting a fix, @peterrrock2. A new release is available now.

[peterrrock2]

No problem @antidipyramid! Glad I could help!