organizing by distance

[gonzo620]

If you want to sort them by distance (closest first), you'll need to create a list of cities and use the list.sort() method. You could append the distance to each line from the file, append them to your lists as you already are, and then use the sort method.

If you only want to report cities within a specified distance, you should add a conditional to only append cities under that distance. Again, you'll want to append the distance to the line.

Something like this should work for the sorting option (you may have to fiddle with the key argument):

with open('cities.txt','r', encoding = 'cp1252') as fin: # opens file with read permission
 
    import math
 
    season = input('Will you take your vacation during summer or winter? ')
    climate = input('Do you want to go to a warm or a cold place? ')
 
    coldsummer = [] # these are empty lists that will be filled in later
    warmsummer = []
    coldwinter = []
    warmwinter = []
         
    data = fin.read().splitlines(True)
     
    for line in data[1:-1]: 
        line = line.split('\t') # splits elements in line with a tab
 
        lat = line[0] # these assign variables to certain parts of the file
        long = line[1]
        city = line[2]
           
        lat_deg = int(lat[0:2].strip('°').strip('N').strip('S')) # strips non integer parts
        lat_min = int(lat[3:5].strip('°').strip('N').strip('S'))
        long_deg = int(long[0:2].strip('°').strip('E').strip('W'))
        long_min = int(long[3:5].strip('°').strip('E').strip('W'))
 
        lat_DMS = lat_deg + (lat_min/60) # converts to degree-minute-second
        lat_rad = lat_DMS*(math.pi/180) # converts to radian
        long_DMS = long_deg + (long_min/60)
        long_rad = long_DMS*(math.pi/180)
 
        R = 6360 # assumed radius of Earth
        Mercedlat_DMS = 37 + 22/60 # coordinate for Merced, CA in degree-minute-second
        Mercedlat_rad = Mercedlat_DMS*(math.pi/180) # in radians
        Mercedlong_DMS = 107 + 25/60
        Mercedlong_rad = Mercedlong_DMS*(math.pi/180)
 
        distance = 2*R*math.sin(math.sqrt(math.sin((lat_rad - Mercedlat_rad)/2)**2 + # distance formula
                                          math.cos(lat_rad)*math.cos(Mercedlat_rad) *
                                          math.sin((long_rad - Mercedlong_rad)/2)**2))**-1

      line.append(distance)
 
        if lat_deg > 66: # these if statements will fill in lists with appropriate values
            coldsummer.append(line)
            coldwinter.append(line)
        elif lat_deg > 35 and lat_deg < 66:
            warmsummer.append(line)
            coldwinter.append(line)
        else:
            warmsummer.append(line)
            warmwinter.append(line)

        def sortByDistance(cityStats):
            return cityStats[len(cityStats - 1)]

        """ The key argument requires a function or method that will act upon each item in the list.
        The function defined above should suffice in this case.
        In effect, list.sort() does this with more finesse:

            length = len(self)
            for i in range(length):
                if key(self[i]) > key(self[i + 1]):
                    swap(self[i], self[i + 1])
        """
        coldsummer.sort(key = sortByDistance)
        warmsummer.sort(key = sortByDistance)
        coldwinter.sort(key = sortByDistance)
        warmwinter.sort(key = sortByDistance)
      
        for x in warmsummer: # the for loops will take desired list and print values
            if season == 'summer':
                if climate == 'warm':
                    print(x[2])
        for x in coldsummer:
            if season == 'summer':
                if climate == 'cold':
                    print(x[2])
        for x in warmwinter:
            if season == 'winter':
                if climate == 'warm':
                    print(x[2])
        for x in coldwinter:
            if season == 'winter':
                if climate == 'cold':
                    print(x[2])

I understand what this code is doing but the len() command returns this

Error:
line 54, in sortByDistance
    return cityStats[len(cityStats-1)]
TypeError: unsupported operand type(s) for -: 'list' and 'int'