How to go back to the beginning of a loop in python?

Question

My code:

b="y"

ol=[]

#operations list

OPERATIONS = ["-", "+", "*", "/"]

op = input ("Please enter your first calculation\n")

while b=="y":



    ops = op.split(" ")

    #add arguments to list

    for x in ops:
        ol+=x

    if ol[1] in OPERATIONS:

        #make sure operator is an operator

        print()

        #make sure not dividing by zero

        if ol[1] == "/" and ol[2] == "0":

            print("Error")

            b = input("Would you like to do another calculation (y/n)?\n")

            if b == "y":

                op = input("Please enter your calculation:\n")

                continue

            else:
                break
        else:

            n1 = float(ol[0])
            n2 = float(ol[2])

            #calculations done here

            if ol[1] == '-':

                calc = n1-n2

            if ol[1] == '+':

                calc = n1+n2

            if ol[1] == '/':

                calc = n1/n2

            if ol[1] == '*':

                calc = n1*n2

            print("Result: " + str(calc))

            b = input("Would you like to do another calculation (y/n)?\n")

            if b == "y":

                op = input("Please enter your calculation:\n")

                continue

            else:
                break



    else:
        print("Error")

How do I ensure that the program takes the new operation to the beginning of the loop instead of continuing to print the original calculation?

Answer 1

您需要在while循环中重置ol=[]

Answer 2

Your calculation is performed using a list of operations ol generated from the variable ops which is taken by splitting input ops by a space.

You can achieve this by moving the ol=[] into the loop:

b="y"
# Remove ol=[]

#operations list
OPERATIONS = ["-", "+", "*", "/"]

op = input ("Please enter your first calculation\n")

while b=="y":
    ol = [] # Add here

However, there is a simpler approach. The variable ops contains a list of operations from the split ( str.split generates a list), and you're then copying this value into the list ol . Instead you can split the string straight into the variable ol as follows:

b="y"

#operations list
OPERATIONS = ["-", "+", "*", "/"]

op = input ("Please enter your first calculation\n")

while b=="y":
    ol = op.split(" ")

This is neater, as you then don't require the extra ops variable.