Finding closest match of Latitude & Longitude in a list of Lat/Longs python

Question

I am trying to find a quicker way to find the closest match of Latitude & Longitude in a list of Lat/Longs from a massive file where I have to open a csv file, convert it to the correct format. Choose the columns my lat and long are located and then plug them into my eqation...if it works. This is what I have so far...I keep getting

TypeError: float object is not subscriptable

def menu3(data):
    lat2 = 47.488611
    long2 = -117.578611
    data = open('eqdata.csv', 'r')
    reader = data.readlines()
    for line in reader:
        lat1 = line[4]
    for line in reader:
        long1 = line[5]
    for ix in range(len(long1)):
        lat1[ix][5]=int(long2[ix][5])

    for ix in range(len(lat1)):
        lat1[ix][4]=int(lat1[ix][4])

    distance =int((lat2-lat1)**2)**.5+int((long2-long1)**2)
    distanceSq = distance**2
    print (distanceSq)

Answer 1

reader = data.readlines() reads all the lines of the file into aa list of strings.

These lines:

for line in reader:
    lat1 = line[4]

assign lat1 to the 5th character of each line...but it loops until the last line, resulting in lat1 being the 5th character of the last line in the file...probably not what you want.

This doesn't even seem to be the code that gives you that error message, because given an input file this line:

    lat1[ix][5]=int(long2[ix][5])

Since lat1 is a single character, should give:

IndexError: string index out of range

long2 is a float value assigned earlier, so indexing it would fail as well.

Update your question with the actual source, sample input and a full traceback of the error message for better help.

There is also a csv module that helps process .csv files, but still need some sample input.

Also I suggest using a debugger, or at least some print statements, to see what your variables are doing.