Compute variance of a list in Python

Task

Given a Python list of numbers (ints/floats), write code to compute its variance.

Requirements

• Input: nums: list[float] (length (n\ge 1))
• Clarify whether you are computing:
• Population variance: (\sigma^2 = \frac{1}{n}\sum_{i=1}^n (x_i-\bar{x})^2), or
• Sample variance: (s^2 = \frac{1}{n-1}\sum_{i=1}^n (x_i-\bar{x})^2) (requires (n\ge 2))
• Avoid using numpy/pandas unless explicitly allowed.
• State time and space complexity.

Follow-ups (optional)

• Implement a numerically stable one-pass version.
• Handle edge cases (empty list, single element, very large numbers).