Append 放到 .txt 文件的底部

Question

i have a script which takes and records payments. I have created a.txt file to hold transaction information and the code looks like:

payment_file = open('Payments.txt', 'w')
payment_file.write('Card no: {} | Amount: £{}\n'.format('XXXX-XXXX-XXXX-' + card_number[-4:], "{:,.2f}".format(amount)))
payment_file.close() 

As an example when i open the txt it will appear as

Card no: XXXX-XXXX-XXXX-1234 | Amount: £15.00

However once one payment is finished the script loops back to the start allowing for another payment to be made but once the next payment is made and you open the.txt the old payment just gets replaced by the most recent one, how would you make sure the payments just get appended underneath eachother

Answer 1

You need to change this:

payment_file = open('Payments.txt', 'a')          # ----------> Here a means appending and not overwriting the existing content.
payment_file.write('Card no: {} | Amount: £{}\n'.format('XXXX-XXXX-XXXX-' + card_number[-4:], "{:,.2f}".format(amount)))
payment_file.close() 

Answer 2

You need to use append. Append adds data to the end of files. Write writes over the whole file. Please see the following Python documentation for reading and writing to files: https://docs.python.org/2/tutorial/inputoutput.html#reading-and-writing-files