The second type of error is a runtime error. A program with a runtime error is one that passed the interpreterβs syntax checks, and started to execute. However, during the execution of one of the statements in the program, an error occurred that caused the interpreter to stop executing the program and display an error message. Runtime errors are also called exceptions because they usually indicate that something exceptional (and bad) has happened.
The following program contains various runtime errors. Can you spot any of them? After locating the error, run the program to see the error message. Can you correct the errors?
Note that the error message for a runtime error will identify the line number where the error occurred, but the root cause of the error may be elsewhere. For example, the program above tries to multiply a user-entered numerical value by 0.08, but does not first convert the user input from string to float. An error will occur on line 2 where the multiplication is attempted, but the real problem is not the multiplication - itβs the missing type conversion.
Python cannot reliably tell if you are trying to divide by 0 until it is executing your program (e.g., you might be asking the user for a value and then dividing by that valueβyou cannot know what value the user will enter before you run the program).
Forgetting the closing parenthesis ) on a print statement.
This is a problem with the formal structure of the program. Python knows that each opening parenthesis must have a corresponding closing parenthesis, and can detect when one is missing simply by looking at the code without running it.
Forgetting to divide by 100 when printing a percentage amount.
This will produce the wrong answer, but Python will not consider it an error at all. The programmer is the one who understands that the answer produced is wrong.
Your teacher and instructor may be able to find most of your runtime errors, but only because they have experience looking at code and possibly writing code. With experience runtime errors are easier to find. But we also have an automated way of finding these types of errors.