pyExercise

# Code by a student, with comments by me

while True:
    print("Select operation.")
    print("1.Add      : + ")
    print("2.Subtract : - ")
    print("3.Multiply : * ")
    print("4.Divide   : / ")
    print("5.Power    : ^ ")
    print("6.Remainder: % ")
    print("7.Terminate: # ")
    print("8.Reset    : $ ")
    choice = input("Enter choice(+,-,*,/,^,%,#,$): ")
    if (choice) == "#":                                 # () not needed around choice
        print("Done. Terminating")
        exit()                                          # break would be better
    elif (choice) == "$":
        True                                            # the word "True" on its own doesn't make sense
                                                        # what are you wanting to set to True?

    # you ask the user to enter + - * / etc. but then you check for 1 to 8
    elif choice in ('1', '2', '3', '4', '5', '6', '7', '8'):

        # You should write a function for getting a float from the user
        # That function needs to do the necessary validation before attempting to construct a float
        num1 = float(input("Enter first number: "))
        num2 = float(input("Enter second number: "))

        # you need to write the functions add(), subtract() etc.
        # "select_op()" is undefined
        if (select_op(choice) == 1):
            print(num1, " + ", num2, " = ", add(num1, num2))
        elif (select_op(choice) == 2):
            print(num1, " - ", num2, " = ", subtract(num1, num2))
        elif (select_op(choice) == 3):
            print(num1, " * ", num2, " = ", multiply(num1, num2))
        elif (select_op(choice) == 4):
            print(num1, " / ", num2, " = ", divide(num1, num2))
        elif (select_op(choice) == 5):
            print(num1, " ^ ", num2, " = ", power(num1, num2))
        elif (select_op(choice) == 6):
            print(num1, " % ", num2, " = ", remainder(num1, num2))
        elif (select_op(choice) == 7):
            print(num1, " # ", num2, " = ", terminate(num1, num2))
        else:
            # "not a valid number" is confusing. Perhaps you mean "not a valid choice"
            print("Not a valid number,please enter again")

exit()              # As I understand it, exit() is not always available. You could just omit this line.