diff --git a/chapter2/2_4.py b/chapter2/2_4.py
index e9e0b8b..7696c3a 100644
--- a/chapter2/2_4.py
+++ b/chapter2/2_4.py
@@ -17,7 +17,7 @@ def eps_greedy(epsilon, Q):
     if sample<=1-epsilon:
         return i
     else:
-       np.delete(action_space,i)
+       action_space=np.delete(action_space,i)
        return np.random.choice(action_space)
 
 def multi_task(max_iter,task_number,epsilon,arm_number,step_size):
@@ -85,4 +85,4 @@ def multi_task(max_iter,task_number,epsilon,arm_number,step_size):
 epsilon=0.1
 arm_number=10
 step_size=0.1
-multi_task(max_iter,task_number,epsilon,arm_number,step_size)
\ No newline at end of file
+multi_task(max_iter,task_number,epsilon,arm_number,step_size)