Update 0020-valid-parentheses.py

avoid using 'map' as variable name to avoid overriding a built-in

Signed-off-by: Chiao Yang <[email protected]>

Author: ChiaoY

Diff for: python/0020-valid-parentheses.py

@@ -1,13 +1,13 @@
 class Solution:
     def isValid(self, s: str) -> bool:
-        Map = {")": "(", "]": "[", "}": "{"}
+        bracketMap = {")": "(", "]": "[", "}": "{"}
         stack = []
 
         for c in s:
-            if c not in Map:
+            if c not in bracketMap:
                 stack.append(c)
                 continue
-            if not stack or stack[-1] != Map[c]:
+            if not stack or stack[-1] != bracketMap[c]:
                 return False
             stack.pop()