Repetition Based on User Input
We can use function input in a loop to make the chemical formula translation example from Choosing Which Statements to Execute, interactive. We will ask the user to enter a chemical formula, and our program, which is saved in a file named formulas.py, will print its name. This should continue until the user types quit:
| | text = "" |
| | while text != "quit": |
| | text = input("Please enter a chemical formula (or 'quit' to exit): ") |
| | if text == "quit": |
| | print("…exiting program") |
| | elif text == "H2O": |
| | print("Water") |
| | elif text == "NH3": |
| | print("Ammonia") |
| | elif text == "CH4": |
| | print("Methane") |
| | else: |
| | print("Unknown compound") |
Since the loop condition checks the value of text, we have to assign it a value before the loop begins. Now we can run the program in formulas.py and it will exit whenever the user types quit:
| | Please enter a chemical formula (or 'quit' to exit): CH4 |
| | Methane |
| | Please enter a chemical formula (or 'quit' to exit): H2O |
| | Water |
| | Please enter a chemical formula (or 'quit' to exit): quit |
| | …exiting program |
The number of times that this loop executes will vary depending on user input, but it will execute at least once.
..................Content has been hidden....................
You can't read the all page of ebook, please click here login for view all page.