CODEWITHSUNDEEP
python-3.xglobal-variables
Harish
Harish

Reputation: 29

python3 NameError variable not defined

I am getting below error name i is not defined at line i += 1 I tried putting at class Solution level. Getting same error

class Solution:
    def kthSmallest(self, root: TreeNode, k: int) -> int:
        i = 0
        def inOrder(root):
            global i
            if root == None:
                return
            inOrder(root.left)
            i += 1
            if i == k:
                return
            inOrder(root.right)

        inOrder(root)
        return i

Upvotes: 0

Views: 58

Answers (2)

Nibor Ndj
Nibor Ndj

Reputation: 122

The scopes of kthSmallest and inOrder are different. Without specifying i as a global variable in kthSmallest, i won't be known inside inOrder.

Nested functions scopes

For nested functions, you need to declare your global variable in the parent function scope as well. 

    class Solution:

        def kthSmallest(self, root: TreeNode, k: int) -> int:
            global i
            i = 0

            def inOrder(root):
                global i
                if root is None:
                    return
                inOrder(root.left)
                i += 1
                if i == k:
                    return
                inOrder(root.right)

            inOrder(root)
            return i

Remark 1

It looks like you are using a class in your example. You could also have done the following:

    class Solution:
        self.i = 0
        def kthSmallest(self, root: TreeNode, k: int) -> int:
            self.i = 0 

            def inOrder(root):
                if root is None:
                    return
                inOrder(root.left)
                self.i += 1
                if self.i == k:
                    return
                inOrder(root.right)

            inOrder(root)
            return i

Upvotes: 0

chepner
chepner

Reputation: 532418

There is no global i. The variable you want is in the non-local enclosing scope.

class Solution:
    def kthSmallest(self, root: TreeNode, k: int) -> int:
        i = 0
        def inOrder(root):
            nonlocal i
            if root == None:
                return
            inOrder(root.left)
            i += 1
            if i == k:
                return
            inOrder(root.right)

        inOrder(root)
        return i

Upvotes: 1

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