Section 15: Handling Exceptions

Question 1

Recall

How to raise exceptions

Answer 1

Recall: Raising Exceptions
Communicate something: decide to deliberately stop execution of code by raising exception

```python
raise<some_exception>(message)
~~~</some_exception>

Question 2

What is the purpose of a try/except block?

Answer 2

Instead of having a ValueError message and the program crashing.

Instead, ValueError will be caught by the except ValueError’ instruction and whatever is written inside will be executed

• try/except blocks allow us to try some code, and if an exception is raised we can catch it and execute different code
• Exception that is caught will not cause the program to crash
• Why?
  
  1. Do not want to hide bugs
  2. Want to use to handle exceptions you cannot prevent as a programmer

Question 3

What are the steps to handle unavoidable errors?

Answer 3

1. Identify the code that can potentially produce the error
2. Put in try block
3. Write code in except block to handle case when error occurs

Question 4

What is the default except block?

Answer 4

Question 5

What to do with multiple exceptions?

Answer 5

For multiple exceptions, want to write single except clause to handle multiple exceptions, you can do so by listing all the exceptions in a tuple

Question 6

General Error Catching:

Answer 6

• Want catch all possible exceptions with same block
• Should not be done often → want to be as specific as possible when catching an exception

```python
try:
# code might be problematic
except:
# what to do in case of issue
#Whatever comes after
~~~

Question 7

What is the finally block?

Answer 7

• After try and except blocks optional finally block can be added
• Finally block always executes whether or not there is an exception
  
  • It also executes even if there is a return/continue/break statement in any try/except block, or if an exception occurs in except block
• Useful for cleanup