How to delete an entry from a dictionary in Python?

Python Calculator Help?

• I'm creating a calculator and i ran into a problem. When the users enters an expression and hits equal. If they click on a number right after that, i want to delete the answer to the previous expression and insert the number. And let's say they want to do an operation on that answer, then they'll click on an operation and the entry text won't be deleted,only when they click a number. Please help.

• Answer:

  I don't know how exactly you have your program designed, but I would assume you could just create a sentinel variable (some sort of variable to keep track of the state of the program) to indicate whether equal has been pressed. Basic logic (used underscores to represent tabs so it's readable): equalWasPressed = False if equal is pressed: __perform calculation __equalWasPressed = True if operatorWasPressed: __if equalWasPressed: ____use previous result in operation __elif numberHasBeenEntered: ___use number that was entered __else: ____invalid syntax if numberWasPressed: __if equalWasPressed: ____overwrite old result with new number