Updates to stack.py -thanks @MrDupin

Signed-off-by: IanDoarn <ian.doarn@zimmerbiomet.com>

Author: IanDoarn

pygorithm/data_structures/stack.py

@@ -95,7 +95,7 @@ def __is_operand(char):
         # OLD VERSION
         # return ord(char) >= ord('a') and ord(char) <= ord('z') \
         #        or ord(char) >= ord('A') and ord(char) <= ord('Z')
-        return True if ord(char) in [ord(c) for c in list(ascii_letters)] else False
+        return True if ord(char) in [ord(c) for c in ascii_letters] else False
 
     @staticmethod
     def __precedence(char):
@@ -127,7 +127,8 @@ def infix_to_postfix(self):
                     postfix.append(top_operator)
                     top_operator = self.my_stack.pop()
             else:
-                while not self.my_stack.is_empty() and self.__precedence(self.expression[i] <= self.__precedence(self.my_stack.peek())):
+                while not self.my_stack.is_empty() \
+                        and self.__precedence(self.expression[i] <= self.__precedence(self.my_stack.peek())):
                     postfix.append(self.my_stack.pop())
                 self.my_stack.push(self.expression[i])