Geocoding

Geocoding is the process of turning an address -- '3020 W Colorado Ave, Colorado Springs, CO 80904' -- into a latitude/longitude coordinate pair. You'd need to do this if you wanted to do some geospatial analysis or make an interactive map or something.

We're going to use the geopy library to geocode a CSV of payday lenders in Illinois. The data file is at data/payday.csv.

Once we have the coordinates, we're going to tack on those columns and write out to a new file, payday-geocoded.csv.



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# import the Google geocoder from geopy
# import Python's csv and time libaries
from geopy.geocoders import GoogleV3
import csv
import time

# Make a geolocator object
# Set the `timeout` keyword argument to 5 (seconds)
geolocator = GoogleV3(timeout=5)

# in a `with` block, open the file to read from and the file to write to
with open('data/payday.csv', 'r') as infile, open('payday-geocoded.csv', 'w') as outfile:    
    
    # make a DictReader object
    reader = csv.DictReader(infile)
    
    # define the headers
    headers = reader.fieldnames + ['lat', 'lng']
    
    # make a DictWriter object
    writer = csv.DictWriter(outfile, fieldnames=headers)
    
    # write headers
    writer.writeheader()
    
    # loop over address data
    # i'm adding an `enumerate()` function to keep track of where we're at
    # so we can kill the loop after 5 iterations --
    # that way we don't bombard google and get cut off
    for i, row in enumerate(reader):
        
        if i < 5:

            # Put the address in a Google-recognizable string: ADDRESS, CITY, STATE ZIP
            addr = '{} {} {}, {}, {}'.format(
                row['STADDR'].strip(),
                row['STADDR2'].strip(),
                row['CITY'],
                row['STATE'],
                row['ZIP']
            )

            # Geocode that string
            location = geolocator.geocode(addr)

            # print the address and results
            print(addr, location.latitude, location.longitude)
            
            # write out a new dict
            writer.writerow({
                **row,
                **{'lat': location.latitude, 'lng': location.longitude}
            })

            # Before we do all of this with the next row, pause for two seconds.
            time.sleep(2)
            
        else:
            # once we hit 5, break out of the loop
            break

# let us know when we're done
print('All done!')



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