python product input example

#!/bin/env python3

if __name__ == "__main__":

    # a stands for append mode, meaning that everything written
    # will be added to the end of the file
    with open("products.txt", "a") as f:
        # go to the end of the file.
        # if the file is epmty, we are at the beginning of the file,
        # otherwise we add lines to the end of the file.
        # seek(offset[, whence])
        # The default value for whence is SEEK_SET. Values for whence are:
        #   SEEK_SET or 0 – start of the stream (the default); offset should be zero or positive
        #   SEEK_CUR or 1 – current stream position; offset may be negative
        #   SEEK_END or 2 – end of the stream; offset is usually negative
        absolute_pos = f.seek(0, 2)

        if absolute_pos == 0:
            # if end of file is actually the beginning of the file:
            # add a header
            # \t is a tab character, \n is a newline character indicating a linebreak
            f.write("id\tname\tprice\n")

        while True:
            try:
                # if the conversion from input string to int or float fails,
                # an exception is raised by python, that we catch
                product_id = int(input("Please enter the product id: "))
                product_name = input("Please enter the product name: ")

                # in some regions a decimal comma is used instead of a decomal point
                product_price = input("Please enter the product price: ").replace(",", ".")
                product_price = float(product_price)
            except Exception as e:
                # catches any exception raised
                #print(e) # you can print what kind of errors are raised if you want to see for yourself
                print("An error occurred, please enter the product again.")
                # goes back to the beginning of the loop and retries the input process

                # here you could add a prompt, whether the user wants to actually continue
                # and if not, you break free from the while loop.
                continue

            line_to_append_to_file = f"{product_id}\t{product_name}\t{product_price}\n" # needs python >= 3.6
            #line_to_append_to_file = "{id}\t{name}\t{price}\n".format(id=product_id,name=product_name, price=product_price) # works with python >= 3.0

            # write tab separated information to file
            f.write(line_to_append_to_file)
            print("Appending: ", line_to_append_to_file)


            confimation = input("Do you want to enter another product?[Y/n]: ")
            # removes whitespace and newline characters if there are any before or after the input string
            confimation = confimation.strip()

            if confimation == "" or confimation.lower() == "y":
                # simply "enter"/"newline" or "Y"/"y" will allow to enter another item
                continue
            else:
                # anything else will abort the while loop.
                break