Code work in VScode but get error in leetcode

Question

"""
14. Longest Common Prefix
Write a function to find the longest common prefix string amongst an array of strings.
If there is no common prefix, return an empty string "".
"""

class Solution:
    def longestCommonPrefix(self,strs: list[str]) -> str:
        list_length = len(strs)
        shortest_length = len(strs[0])
        for i in range(list_length):
            length = len(strs[i])
            if shortest_length > length:
                shortest_length = length
                shortest_char = strs[i]

        char = [0]*len(shortest_char)
        for i in range(shortest_length):
            for str in strs:
                if str[i] == shortest_char[i]:
                    char[i] +=1

        for i in range(shortest_length):
            if char[i] < list_length:
                char_list = list(shortest_char)
                return "".join(char_list[:i])
                

print(Solution.longestCommonPrefix(None,["flower","flow","flight"]))

result :

enter image description here

but in vscode ,i get an error :

UnboundLocalError: cannot access local variable 'shortest_char' where it is not associated with a value
                   ^^^^^^^^^^^^^
    char = [0]*len(shortest_char)
Line 11 in longestCommonPrefix (Solution.py)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ret = Solution().longestCommonPrefix(param_1)
Line 46 in _driver (Solution.py)
    _driver()
Line 61 in <module> (Solution.py)

How can i solve this problem? In vscode, it goes through 3 for loop without any issue. I think in leetcode, it cant get variable between for loop, but why?

Answer 1

if shortest_length <= length than your shortest_char variable will not be defined. It is bad practice to define variables like that.