diff --git a/population.py b/population.py
index 3e78cc9abd6794c5e926e9ff50c58845a5f48241..424431216c8838e725049c0738c640b05fc479ab 100644
--- a/population.py
+++ b/population.py
@@ -15,7 +15,10 @@ class Population:
         self.indiv = liste_individus
         return self
 
-    def selection_p_best(self,p=self.n//2):
+    def selection_p_best(self,p=None):
+        if p==None:
+            p=(self.n)//2
+            
         def tri_rapide_aux(tableau,debut,fin):
             if debut < fin-1:
                 positionPivot=partitionner(tableau,debut,fin)