diff --git a/expression.py b/expression.py
index 0c330e3..186c43e 100644
--- a/expression.py
+++ b/expression.py
@@ -3,30 +3,30 @@ import re
 class Token:
     OPERAND_ADDITION = "+"
     OPERAND_MULTIPLICATION = "*"
-    NUMBER = re.compile(r"^\\d+$") #CHANGER
+    NUMBER = re.compile(r'\d+') #CHANGER
 
 class Expression:
 
     def __init__(self, val, gauche=None, droite=None):
-        if Token.NUMBER.match(str(val)) and (gauche != None or droite != None):
+        if Token.NUMBER.search(str(val)) is not None and (gauche != None or droite != None):
             raise AttributeError("gauche et droite ne peuvent pas exister si val est un nombre")
         self.val = val
         self.gauche = gauche
         self.droite = droite
 
-    def evalue(self, this):
-        #if Token.NUMBER.match(str(this.val)):
-        print(this.val)
-        #    return int(this.val)
-        if this.val == Token.OPERAND_ADDITION:
-            return this.evalue(this.gauche) + this.evalue(this.droite)
-        elif this.val == Token.OPERAND_MULTIPLICATION:
-            return this.evalue(this.gauche) * this.evalue(this.droite)
+    def evalue(self):
+        if self.val == Token.OPERAND_ADDITION:
+            return self.gauche.evalue() + self.droite.evalue()
+        elif self.val == Token.OPERAND_MULTIPLICATION:
+            return self.gauche.evalue() * self.droite.evalue()
         else:
-            return int(this.val)
+            return int(self.val)
 
-    def __str__():
-        pass
+    def __str__(self):
+        if Token.NUMBER.match(string=self.val) is not None:
+            return self.val
+        return "(" + self.gauche.__str__() + self.val + self.droite.__str__() + ")"
+        
 
 exp = Expression('*',
 Expression(6, None, None),
@@ -34,4 +34,5 @@ Expression('+',
 Expression(4, None, None),
 Expression(3, None, None)
 ))
-print(exp.evalue(exp))
\ No newline at end of file
+print(exp.evalue())
+print(str(exp))
\ No newline at end of file