Estimate population inside and outside isochrone for each census variable

[MicheleTobias]

It looks like this script depends on an environment you've set up specifically for your computer. Let's find a way to make the loading of data more universal. Let's assume all data you load is in a data folder in a working directory of your choosing and that your API key is stored in a text file in the root of the working directory.

[MicheleTobias]

So the assumed file structure might look like this:

working_directory
   |___ data
            |___ 60_min_isochrone
            |___ 90_min_isochrone
            |___ 120_min_isochrone
   |___ api_key.txt
   |___ census_variables.csv