Solving the NameError Issue in Your LeetCode Python Solution

Discover why you're encountering the `NameError` in your LeetCode submissions and how to effectively fix recursive methods within class structures in Python.
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Solving the NameError Issue in Your LeetCode Python Solution

If you've been working on problems in LeetCode, you might have come across an error message that reads, NameError: global name 'climbStairs' is not defined. It can be puzzling, especially when your code seems logical. In this guide, we'll explore the root cause of this error and offer a clear, step-by-step solution.

Understanding the Problem

The Code Snippet

You might have written a code snippet like this:

[[See Video to Reveal this Text or Code Snippet]]

When you attempt to call this function, you receive the NameError. The error message indicates that Python doesn't recognize climbStairs as a defined name.

What’s Going Wrong?

The issue arises from the fact that inside the climbStairs method, you're trying to call climbStairs(n-2) and climbStairs(n-1) without specifying that it's a method of the current class instance. In Python, when you define a method inside a class, you need to use the instance (referred to by self) to call other methods of that class.

The Solution

Correcting the Code

To fix the error, simply replace your recursive method calls as follows:

[[See Video to Reveal this Text or Code Snippet]]

Output Explanation

When you run this corrected code, the output will be:

[[See Video to Reveal this Text or Code Snippet]]

Key Points to Note

Use of self: The keyword self refers to the instance of the class. It allows access to attributes and methods within the class context. Using self is crucial when you want to refer to another method of the same class.

Why Does it Work Without Class and Self?

When you moved the climbStairs function outside of the class structure and removed the self keyword:

[[See Video to Reveal this Text or Code Snippet]]

This worked because there was no class context to handle. In standalone functions, you can call them directly without needing self.

Conclusion

By understanding how Python manages function scope and the importance of the self keyword in class methods, you can effectively avoid common pitfalls such as NameError. Always remember to prepend self. when calling other methods within the same class.

Happy coding, and best of luck with your challenges on LeetCode!