Python Tutorial: Census Geography

Key Takeaways

census data are available from many different geographic levels from the nation down to the census block in this lesson we will learn about these geographies so far we have been requesting all US states at once but what if we only want the data for one state say Pennsylvania in that case replace the star wildcard with the state code 42 this is the geographic identifier or geo ID for Pennsylvania where can we find these identifiers although there are many sources online in this lesson you will use the geographic codes lookup website maintained by the Missouri census data center the Bureau reports summary statistics for both legal and statistical geographies legal administrative geographies are those that exist as legally defined entities such as States or counties statistical geographies which include census tracts are created by the Census Bureau for the purposes of statistical reporting zip code tabulation area or zip de is a statistical equivalent to the postal zip codes these geographies exist in a hierarchy with larger units built from smaller units census blocks are the smallest reporting unit and the building block for all other geographies in this image the connecting lines indicate nesting so blocks nest in block groups which nest in census tracts which nest in counties but school districts shown in green in the middle left of the chart can cross county lines so only blocks nest in school districts we can use this information to specify a containing geography using the optional in predicate here we request all counties in two states New Hampshire and Vermont you cannot use a wild-card with the in predicate you can also request specific counties in one state if you specify Geo IDs in the four predicate you cannot use the in predicate to request more than one containing geography after the in predicate has been assigned use request get to return a response object the same as before place is a special geography that combines legal and statistical areas it includes incorporated places legally existing municipal governments and census-designated places these are defined in cooperation with local officials to provide data for areas that have a commonly used name but are not legally incorporated CBP's can be quite large for example the city of Los Angeles is an incorporated place east los angeles is a census-designated place in los angeles county both are included if you request data for places in California this is a partial list of geographies available via API for the 2010 census the API does not expose all geographies that the Census Bureau reports on and the geographies differ by data product you can view the list for any data product by appending geography dot HTML to the API base URL an example for the 2010 decennial census is shown here you will get familiar with these and other geographies throughout this course what about requesting data for geographies that don't nest cleanly for example the state congressional district county hierarchy first the four predicate must be set to county parentheses or part not just county you must specify geo IDs for each level up the hierarchy state : 42 semicolon congressional district : 0 to request counties in the 2nd congressional district in the state of Pennsylvania the result shows the two counties in the 2nd district but the names indicate that they are part counties demographic data is reported only for the parts of these counties that fall in the second District you've learned about some important geographies for reporting census data let's get some hands on