how can i make this list merger and use user input to decide what sorting order is displayed-CodePudding

i have posted this code on here before, i would like to know how i can make this code function. i have 3 different lists, a merging function to combine any objects with the same name and there values, i have a user input section where i ask the user what sorting method they would like (i would also like to add a numerical function as well). and the user input is there as well. i dont know how to compile all of this code into a working model.

`fruit= [["apples", 5], ["pears", 10], ["oranges", 6], ["bananas", 12], ["grapes", 100]]

items= [["cars",3], ["sheets",5], ["bananas",8], ["bridges",17], ["roads",0], ["doors",1]]

colours= [["blue",1], ["black",7], ["orange",13], ["yellow",2], ["red",8], ["blue",5]]

merge = fruit   items   colours
result = set(
    (item, sum(quantity for label, quantity in merge if label == item))
    for item, _ in merge
)

print ()        
print ("SHOW DATA")
print ()

print ("fruit :", fruit)
print ("items :", items)
print ("colours :", colours)

print ()
print ("WHICH ORDER?")
print ()

print ("1 = Alphabetically Ascending")
print ("2 = Alphabetically Descending")
print ("")
SortOrder = int(input ("Enter the sort order you prefer for the merged data >"))

if (SortOrder == 1):
    result.sort()
    for l in lists:
       print(l)

elif (SortOrder == 2):
    result.sort(reverse=True)
    for l in lists:
       print(l)

CodePudding user response：

A set does not have the .sort() method, you need to use the sorted() method, and you are looping through lists which in not defined.

Here is a solution :

if (SortOrder == 1):
    lists = sorted(result)
    for l in lists:
       print(l)
elif (SortOrder == 2):
    lists = sorted(result, reverse=True)
    for l in lists:
       print(l)

CodePudding user response：

You currently build result by iterating over all the lists once (to calculate the sum) for every element in all the lists, which makes it an O(n^2) operation. Instead, iterate over all the lists once for O(n), and build a dictionary out of the key-value pairs.

result = {}
for key, value in merge:
    if key in result:
        result[key]  = value
    else:
        result[key] = value

Which gives the following result:

{'apples': 5, 'pears': 10, 'oranges': 6,
 'bananas': 20, 'grapes': 100, 'cars': 3,
 'sheets': 5, 'bridges': 17, 'roads': 0,
 'doors': 1, 'blue': 6, 'black': 7,
 'orange': 13, 'yellow': 2, 'red': 8}

Next, you want to take the user's input to decide how to sort your output. We can sort just by calling sorted on result.items(), which is a collection of the key-value pairs in the dictionary. Read about the sorted function here: https://docs.python.org/3/howto/sorting.html

print("1: Sort by name, ascending")
print("2: Sort by name, descending")
print("3: Sort by value, ascending")
print("4: Sort by value, descending")

sort_order = int(input("Enter sort order: "))

# Sort by value if input is 3 or 4
sort_numeric = (sort_order > 2)

# Sort descending if input is even
sort_reversed = (sort_order % 2 == 0)

sort_reversed is now a boolean value that tells you what the reverse argument to sorted() should be.

Let's sort the items in our dictionary. To sort the items numerically, we use the key argument to the sorted function. This key needs to be a function, which is given one argument -- the element that is being sorted -- and returns the value to sort it by -- the 1th element (i.e. the value part) of the key-value pair in the dictionary:

if sort_numeric:
    sorted_result = sorted(result.items(),
       reverse=sort_reversed,
       key=lambda kvp: kvp[1])
else:
    sorted_result = sorted(result.items(),
       reverse=sort_reversed)

And let's print our output:

for item, qty in sorted_result:
    print(f"{item}\t{qty}")

For an input of 4, we get this output:

grapes  100
bananas 20
bridges 17
orange  13
pears   10
red 8
black   7
oranges 6
blue    6
apples  5
sheets  5
cars    3
yellow  2
doors   1
roads   0