def ex1(x,y,z): #returns (x/y) ** z if y is not equalt to 0 k = -1 if y != 0: x = float(x) k = (x/y)**z else: print 'Error' return k def ex2(s,n): #returns the nth character of a given string, or -1 does not correspond to a character k =- 1 if n > len(s) or n < 1: return -1 else: return s[n-1],n def ex3(): #returns the product of x and y the first time that is positive along with the number of user's attempts x = float(raw_input('give 1st number:')) y = float(raw_input('give 2nd number:')) counter = 0 while (x * y) >= 0: print 'error - give again numbers' print x = float(raw_input('give again 1st number:')) y = float(raw_input('give again 2nd number:')) counter += 1 return (x*y) , counter ############################################################# n1 = ex1(4,2,3) n2 = ex1(5,0,10) print n1 , n2 ########### x1,x2 = ex2('python',3) print ex2('PAOK',13) print x1,x2 ########### k = ex3() print 'the returned product equals to %f and user made %d attempts. ' %(k[0] , k[1])