Python can print but cannot return statement

Question

New user, please go easy on me. Currently attempting leetcode twosum example and cannot return a statement. Oddly it prints when swapped out to the print keyword. The input example is [3,3] and should return [1,0] or [0,1] when the statement is returned. Looking at other questions on S/O it has to do with the subcall returning to the original loop but i still don't fully understand. Any tips?

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        self.nums = nums
        self.target = target
        nums = tuple(nums) #issue happens as a tuple and list.
        for x in nums:
            for y in nums:
                if (x+y) == target:
                    #print ([x,y])
                    if (nums.index(x)!=nums.index(y) ):
                        return([nums.index(x), nums.index(y)]) #this statement will normally print
                                                               # are any of the lines below necessary?
                    else:
                        continue
                    return

Passing [3,3] as a List serves as an input. The output is an empty list. "[]" — brayson211
– brayson211, Commented May 3, 2022 at 1:02
The answer to "are any of the lines below necessary?" is no. :) You'll never reach the return, and without that you'll just continue the loop regardless of the else. — Samwise
– Samwise, Commented May 3, 2022 at 1:03

C.Nivs · Accepted Answer · 2022-05-03 01:03:04Z

2

Because the values are the same, nums.index(3) will always equal nums.index(3) since it will always find the first 3. To fix this, use enumerate to track the indices separately:

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        for i, x in enumerate(nums):
            for j, y in enumerate(nums):
                if (x+y) == target:
                    if i != j:
                        return([i, j])

answered May 3, 2022 at 1:03

C.Nivs

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1 Comment

brayson211 Over a year ago

I appreciate the help everyone, thank you for the swift answers.

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