# GBTownsSortedByIncreasingPopulation
# Reads and sorts data in order of increasing population
# Writes this data to a seperate file

# Empty arrays for file
place = [];
Type = [];
population = [];
latitude = [];
longitude = [];

opened = 0

try:
    readFile = open('GBplaces.csv','r');
    opened = 1
except:
    print('Could not open file.');

# Skips headings of file

next(readFile);

# Using this as a check to see if the correct file is opened
# Also used to see if it has sorted in right order when written

if opened:
    for line in readFile:
        splitUp = line.split(',');
        place.append(splitUp[0]);
        Type.append(splitUp[1]);
        population.append(int(splitUp[2]));
        latitude.append(splitUp[3]);
        longitude.append(splitUp[4]);
        print(splitUp[0] + ',' + splitUp[1] + ',' + splitUp[2] + ',' + splitUp[3] + ',' + splitUp[4]);

Headings = readFile.readline();
readFile.close();

# Write a file which is sorted in population ascending order
writeFile = open('GBplacesSorted.csv','w');

# sort population in acsending numerical order
sortpopulation = sorted(population);

# sort each other array by zipping it with sorted population
sortedplace = [place for (population,place) in sorted(zip(population,place), key=lambda pair: pair[0])];
sortedType = [Type for (population, Type) in sorted(zip(population, Type), key=lambda pair: pair[0])];
sortedlatitude = [latitude for (population,latitude) in sorted(zip(population, latitude), key=lambda pair: pair[0])];
sortedlongitude = [longitude for (population, longitude) in sorted(zip(population, longitude), key=lambda pair: pair[0])];

# write a file which lists towns and cities in order of population (plus other info)
writeFile.write(Headings);
for i in range(0,len(place)):
    writeFile.write(str(sortedplace[i]) + ',' + str(sortpopulation[i]) + ',' + str(sortedType[i]) + ',' + str(sortedlatitude[i]) + ',' + str(sortedlongitude[i]));
writeFile.close();