Obtaining values from columns

[oncebuddy]

I want to obtain the top 3 cities and items based on their sales, but the only thing I can do now is return the all cities and items with their respective sales. Without using dict, how do I obtain my desired output? Or if I use dict, how do I obtain the desired output?

purchases.txt

    2012-01-01	09:00	San Jose	Men's Clothing	214.05	Amex
    2012-01-01	09:00	Fort Worth	Women's Clothing	153.57	Visa
    2012-01-01	09:00	San Diego	Music	66.08	Cash
    2012-01-01	09:00	Pittsburgh	Pet Supplies	493.51	Discover
    2012-01-01	09:00	Omaha	Children's Clothing	235.63	MasterCard
    2012-01-01	09:00	Stockton	Men's Clothing	247.18	MasterCard
    2012-01-01	09:00	Austin	Cameras	379.6	Visa
    2012-01-01	09:00	New York	Consumer Electronics	296.8	Cash
    2012-01-01	09:00	Corpus Christi	Toys	25.38	Discover
    2012-01-01	09:00	Fort Worth	Toys	213.88	Visa

test.py

        f = open ("purchases.txt")
            
        def separator():
            str = ("="*48)
            print (str)
            return;
        
        city_seen = set()
        item_seen = set()
        
        citysaleslist = []
        itemsaleslist= []
        
        for line in open(sys.argv[1]):
        
            sales=float(line.split()[-2]) 
              
            strsales=line.split()[-2]
        
            city=line.split('\t')[2] 
            item=line.split('\t')[3]
        
            if city not in city_seen: # if city is not a duplicate, add to city_seen set
        
                city_seen.add(city)
    
            #Pressing tab for the bottom 2 lines will remove duplicate but combining the sales for the duplicates is impossible here.
            citysales="{0:<29}{1:>18}".format(city,strsales)
            citysaleslist.append(citysales)
        
       
            if item not in item_seen: # if item is not a duplicate, add to item_seen set
        
                 item_seen.add(item)
     
            #Pressing tab for the bottom 2 lines will remove duplicate but combining the sales for the duplicates is impossible here.
            itemsales = "{0:<29}{1:>18}".format(item,strsales)
            itemsaleslist.append(itemsales)
    
    
         print("Top Three Cities \n")
         separator()
              
         for i in citysaleslist:
              
             print(i)
        
        
         separator()
        
        
         print("Bottom Three Cities \n")
         separator()
              
        
         separator()
        
              
         print("Top Three Item Categories")
         separator()
           
         for i in itemsaleslist:
              
         print(i)
        
         separator()
        
        
         print("\nBottom Three Item Categories")
         separator()
           
        
         separator()      
 

My output:

    Top Three Cities 
    
    ================================================
    San Jose                                 214.05
    Fort Worth                               153.57
    San Diego                                 66.08
    Pittsburgh                               493.51
    Omaha                                    235.63
    Stockton                                 247.18
    Austin                                    379.6
    New York                                  296.8
    Corpus Christi                            25.38
    Fort Worth                               213.88
    ================================================
    Bottom Three Cities 
    
    ================================================
    ================================================

   
    Top Three Item Categories
    ================================================
    Men's Clothing                           214.05
    Women's Clothing                         153.57
    Music                                     66.08
    Pet Supplies                             493.51
    Children's Clothing                      235.63
    Men's Clothing                           247.18
    Cameras                                   379.6
    Consumer Electronics                      296.8
    Toys                                      25.38
    Toys                                     213.88
    ================================================
    
    Bottom Three Item Categories
    ================================================
    ================================================

    

Desired output:

    Top Three Cities 
    
    ================================================
    Pittsburgh                               493.51
    Austin                                   379.60
    Fort Worth                               367.45
    ================================================
    Bottom Three Cities 
    
    ================================================
    Omaha                                     235.63
    San Jose                                  214.05
    San Diego                                  66.08
    ================================================


    Top Three Item Categories
    ================================================
    Pet Supplies                             493.51
    Men's Clothing                           461.23
    Cameras                                   379.6
    ================================================
    
    Bottom Three Item Categories
    ================================================
    Toys                                      239.26
    Children's Clothing                       235.63
    Women's Clothing                          153.57
    ================================================
    

[j.crater]

city_seen and item_seen variables are sets, so they keep track of duplicates by default, and you don't need the if statments (e.g. if item not in item_seen).
You open the file (f = open...) but not close it when you are done with using it. I recommend using a context manager, which will close the file automatically when you are done using it. Here is a simple example. You open it again in for loop, I assume (open(sys.argv[1])).

It is probably beyond your current course curriculum, but you could put cities and values in a list of tuples, and use a lambda function to sort them by sales:

sorted([('city1', 95.5),('city2', 26.7),('city3', 248.1), ('city4', 30.9)], key=lambda x: x[1], reverse=True)

I provided the list of tuples here directly, but it will not be hard to write code that will do it for you.