Few corrections

Chapter_2/ex3.py

 import math
 
-step = 1
+step = 1.
 min_step = 1e-10
-x = 0
+x = 0.
 
 while step >= min_step:
     while math.exp(-0.5*x*x) > 0:

Chapter_2/ex5_sol1.py

@@ -20,7 +20,6 @@ while lineId < n_lines:
     colId = 0
     txt_to_print = "|"
     while colId < n_col:
-        t = 0
         filled = False
         x = colId - 0.5
         while x < colId + 0.5:            # Boucle sur x pour avoir une ligne continue

Chapter_2/ex5_sol2.py

@@ -35,5 +35,5 @@ while lineId < n_lines:
         colId+=1
 
     lineId+=1
-    print txt_to_print+"|"
+    print (txt_to_print+"|")
 print(" "+n_col*"-")