Valid Number Python Solution with Tests

lcpy gen -n 65   # by problem number
lcpy gen -s valid_number   # by problem name

Input: s = "0"
Output: true

Input: s = "e"
Output: false

Input: s = "."
Output: false

class Solution:
    # Time: O(n)
    # Space: O(1)
    def is_number(self, s: str) -> bool:
        i, n = 0, len(s)

        def skip_digits() -> bool:
            nonlocal i
            start = i
            while i < n and s[i].isdigit():
                i += 1
            return i > start

        if s[i] in "+-":
            i += 1
        if skip_digits():
            if i < n and s[i] == ".":
                i += 1
                skip_digits()
        else:
            if i >= n or s[i] != ".":
                return False
            i += 1
            if not skip_digits():
                return False

        if i < n and s[i] in "eE":
            i += 1
            if i < n and s[i] in "+-":
                i += 1
            if not skip_digits():
                return False

        return i == n