I am currently self-learning python for a career change. While doing some exercises about 'list', I encountered IndexError: list index out of range.
So, I am trying to build a function, that determines which product should be placed on my store's shelves. But, I also put constraints.
- The shelve has a max capacity of 200
- small-sized items should be placed first
- if two or more items have the same size, the item with the highest price should be placed first
As an input for the function, I have a list of tuples "dairy_items", denoted as [(id, size, price)].
This is my code:
capacity=200
dairy_items=[('p1', 10, 3), ('p2', 13, 5),
('p3', 15, 2), ('p4', 26, 2),
('p5', 18, 6), ('p6', 25, 3),
('p7', 20, 4), ('p8', 10, 5),
('p9', 15, 4), ('p10', 12, 7),
('p11', 19, 3), ('p12', 27, 6),
('p13', 16, 4), ('p14', 23, 5),
('p15', 14, 2), ('p16', 23, 5),
('p17', 12, 7), ('p18', 11, 3),
('p19', 16, 5), ('p20', 11, 4)]
def shelving(dairy_items):
#first: sort the list of tuples based on size: low-to-big
items = sorted(dairy_items, key=lambda x: x[1], reverse=False)
#second: iterate the sorted list of tuples.
#agorithm: retrieve the first 2 elements of the sorted list
#then compare those two elements by applying rules/conditions as stated
#the 'winning' element is placed to 'result' and this element is removed from 'items'. Also 'temp' list is resetted
#do again untill shelves cannot be added anymore (capacity full and do not exceeds limit)
result = []
total_price = []
temp_capacity = []
temp = items[:2]
while sum(temp_capacity) < capacity:
#add conditions: (low first) and (if size the same, highest price first)
if (temp[0][1] == temp[1][1]) and (temp[0][2] > temp[1][2]):
temp_capacity.append(temp[0][1])
result.append(temp.pop(0))
items.pop(0)
temp.clear()
temp = items[:2]
total_price.append(temp[0][2])
elif ((temp[0][1] == temp[1][1])) and (temp[0][2] < temp[1][2]):
temp_capacity.append(temp[1][1])
result.append(temp.pop())
items.pop()
temp.clear()
temp = items[:2]
total_price.append(temp[1][2])
else:
temp_capacity.append(temp[0][1])
result.append(temp.pop(0))
items.pop(0)
temp.clear()
temp = items[:2]
total_price.append(temp[0][2])
result = result.append(temp_capacity)
#return a tuple with three elements: ([list of product ID to be placed in order], total occupied capacity of shelves, total prices)
return result
c:\Users\abc\downloads\listexercise.py in <module>
----> 1 print(shelving(dairy_items))
c:\Users\abc\downloads\listexercise.py in shelving(dairy_items)
28 while sum(temp_capacity) < capacity:
29
---> 30 if (temp[0][1] == temp[1][1]) and (temp[0][2] > temp[1][2]):
31 temp_capacity.append(temp[0][1])
32 result.append(temp2.pop(0))
IndexError: list index out of range
EDIT:
This is the expected result:
#Result should be True
print(shelving(dairy_items) == (['p8', 'p1', 'p20', 'p18', 'p10', 'p17', 'p2', 'p15', 'p9', 'p3', 'p19', 'p13', 'p5', 'p11'], 192, 60))
CodePudding user response：
The IndexError occured because, you had tried to append the 2nd element after popping it from temp because, after popping it out, there will be only one element in temp which can indexed with 0.
Also I noticed a few more bugs which could hinder your program from giving the correct output and rectified them.
The following code will work efficiently...
from time import time
start = time()
capacity = 200
dairy_items = [('p1', 10, 3), ('p2', 13, 5),
('p3', 15, 2), ('p4', 26, 2),
('p5', 18, 6), ('p6', 25, 3),
('p7', 20, 4), ('p8', 10, 5),
('p9', 15, 4), ('p10', 12, 7),
('p11', 19, 3), ('p12', 27, 6),
('p13', 16, 4), ('p14', 23, 5),
('p15', 14, 2), ('p16', 23, 5),
('p17', 12, 7), ('p18', 11, 3),
('p19', 16, 5), ('p20', 11, 4)]
def shelving(dairy_items):
items = sorted(dairy_items, key=lambda x: x[1])
result = ([],)
total_price, temp_capacity = 0, 0
while (temp_capacity items[0][1]) < capacity:
temp = items[:2]
if temp[0][1] == temp[1][1]:
if temp[0][2] > temp[1][2]:
temp_capacity = temp[0][1]
result[0].append(temp[0][0])
total_price = temp[0][2]
items.pop(0)
elif temp[0][2] < temp[1][2]:
temp_capacity = temp[1][1]
result[0].append(temp[1][0])
total_price = temp[1][2]
items.pop(items.index(temp[1]))
else:
temp_capacity = temp[0][1]
result[0].append(temp[0][0])
total_price = temp[0][2]
items.pop(0)
else:
temp_capacity = temp[0][1]
result[0].append(temp[0][0])
total_price = temp[0][2]
items.pop(0)
result = (temp_capacity, total_price)
return result
a = shelving(dairy_items)
end = time()
print(a)
print(f"\nTime Taken : {end-start} secs")
Output:-
(['p8', 'p1', 'p20', 'p18', 'p10', 'p17', 'p2', 'p15', 'p9', 'p3', 'p19', 'p13', 'p5', 'p11'], 192, 60)
Time Taken : 3.123283386230469e-05 secs
CodePudding user response：
Not sure what the question is, but the following information may be relevant:
IndexError occurs when a sequence subscript is out of range. What does this mean? Consider the following code:
l = [1, 2, 3]
a = l[0]
This code does two things:
- Define a list of 3 integers called l
- Assigns the first element of l to a variable called a
Now, if I were to do the following:
l = [1, 2, 3]
a = l[3]
I would raise an IndexError, as I'm accessing the fouth element of a three element list. Somewhere in your code, you're likely over-indexing your list. This is a good chance to learn about debugging using pdg. Throw a call to breakpoint() in your code and inspect the variables, good luck!
CodePudding user response：
ok, firstly, you should debug your code, if you print temp before adding temp[1][2] to total_price you would see that the last index is what causing the error, the example is here:
capacity=200
dairy_items=[('p1', 10, 3), ('p2', 13, 5),
('p3', 15, 2), ('p4', 26, 2),
('p5', 18, 6), ('p6', 25, 3),
('p7', 20, 4), ('p8', 10, 5),
('p9', 15, 4), ('p10', 12, 7),
('p11', 19, 3), ('p12', 27, 6),
('p13', 16, 4), ('p14', 23, 5),
('p15', 14, 2), ('p16', 23, 5),
('p17', 12, 7), ('p18', 11, 3),
('p19', 16, 5), ('p20', 11, 4)]
def shelving(dairy_items):
#first: sort the list of tuples based on size: low-to-big
items = sorted(dairy_items, key=lambda x: x[1], reverse=False)
#second: iterate the sorted list of tuples.
#agorithm: retrieve the first 2 elements of the sorted list
#then compare those two elements by applying rules/conditions as stated
#the 'winning' element is placed to 'result' and this element is removed from 'items'. Also 'temp' list is resetted
#do again untill shelves cannot be added anymore (capacity full and do not exceeds limit)
result = []
total_price = []
temp_capacity = []
temp = items[:2]
while sum(temp_capacity) < capacity:
#add conditions: (low first) and (if size the same, highest price first)
if (temp[0][1] == temp[1][1]) and (temp[0][2] > temp[1][2]):
temp_capacity.append(temp[0][1])
result.append(temp.pop(0))
items.pop(0)
temp.clear()
temp = items[:2]
total_price.append(temp[0][2])
elif ((temp[0][1] == temp[1][1])) and (temp[0][2] < temp[1][2]):
temp_capacity.append(temp[1][1])
result.append(temp.pop())
items.pop()
temp.clear()
temp = items[:2]
print(temp) # -----------NEW LINE ADDED TO DEBUG YOUR CODE
total_price.append(temp[1][2])
else:
temp_capacity.append(temp[0][1])
result.append(temp.pop(0))
items.pop(0)
temp.clear()
temp = items[:2]
total_price.append(temp[0][2])
result = result.append(temp_capacity)
#return a tuple with three elements: ([list of product ID to be placed in order], total occupied capacity of shelves, total prices)
return result
shelving(dairy_items)
the result i am getting is:
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3), ('p8', 10, 5)]
[('p1', 10, 3)]
Traceback (most recent call last):
File "<string>", line 55, in <module>
File "<string>", line 44, in shelving
IndexError: list index out of range
>
as you see clearly last index [('p1', 10, 3)] has only 1 tuple, hence the IndexError