Raising and Handling Exceptions

Question 1

Exception

Answer 1

An event or error that may cause your program to stop if not properly handled.

“The user provided the wrong data type causing the Traceback to throw a TypeError exception.”

Question 2

Exception Name: NameError

Answer 2

A local or global name is not found.

Question 3

Exception Name: ZeroDivisionError

Answer 3

The second argument of a division or modulo operation is zero.

Question 4

Exception Name: OverflowError

Answer 4

The result of an arithmetic operation is too large to be represented.

Question 5

Exception Name: SyntaxError

Answer 5

The parser encounters a syntax error.

Question 6

Exception Name: TypeError

Answer 6

An operation or function is applied to an object of inappropriate type.

Question 7

Exception Name: KeyboardInterrupt

Answer 7

The user hits the interrupt key (normally Control-C or Delete).

Question 8

TRY and EXPECT

Answer 8

we can handle exceptions using the try and except syntax. 
try: 
if x < 0:
raise ValueError(f"x is too small")
^raise generates the exception
except ValueError as problem:
then do something to handle the exception like 
print(:we had an exception"

Question 9

try:

and

Body of the try-clause

Answer 9

This begins a try-clause. If any exception is raised by any code executed inside the try-clause, the rest of the try-clause is skipped, and code execution moves to the except clause.

The try-clause should include all code that has the possibility of raising an exception that we want to handle. The try-clause is indented once from try:

Question 10

except

Answer 10

A keyword that begins an except-clause. The except-clause will run if a matching exception is raised from the try-clause.

Question 11

ExampleError

Answer 11

Replace this with the type of exception that we are handling, such as NameError or ZeroDivisionError.

Question 12

as

Answer 12

A keyword that designates the caught exception (that matches the type of ExampleError) can be accessed as the local variable to the right.

Question 13

error_as_a_variable:

Answer 13

Replace this with any valid variable name. This variable’s value will be the exception data, and can be accessed inside of the except-clause. err is a common variable name. Don’t forget the :!

Question 14

Body of the except clause

Answer 14

The error clause should include code that needs to execute if an exception is raised. This code can be used for printing or logging details about err. More powerfully, this is where we can try handling the situation and helping the program move on.

Question 15

Handling Multiple Types of Exceptions

Answer 15

If we need to handle more than one kind of exception, we can add an infinite number of except clauses. Much like the if..elif statements, the raised exception will check if it matches one-at-a-time, starting from the top.

Question 16

What is the benefit of using the try…except clause?

Answer 16

Raising and using the try…except clause are great ways to make our code more robust by handling errors before they crash our program.

Question 17

pytest Syntax to write a test that expects a raised exception

Answer 17

we should determine two things:

1) What function call and input do we expect to raise the exception?
2) What kind of exception do we expect from this function call?

With those two pieces of info in mind, we can understand the pytest syntax:

def test_exceptional_function():
    with pytest.raises(SomeTypeOfException):
         exceptional_function(exceptional_argument)