Are Python Exceptions Runtime Errors?

Are Python Exceptions Runtime Errors?

Yes, Python exceptions are considered runtime errors. Most exceptions occur during runtime.

Exceptions in Python are errors that occur when there is an abnormal scenario during the execution of a program, which terminates the execution abruptly, interrupting its normal flow. Examples of exceptions are ZeroDivisionError, IndexError, ValueError, etc..

Whereas, errors in Python are detected before the execution of the program, they include syntactical errors and other violations of the program rules. Examples of errors are SyntaxError, IndentationError, etc. 

Exceptions are Raised at Runtime

Exceptions occur when the execution of the program is interrupted because of issues like logical errors, incorrect data types, or issues with external resources, such as missing files or network failures.

Example: ZeroDivisionError at Runtime

In this example, the error occurs when the code is executed and tries to divide by zero -

a = 10
b = 0

try:
   result = a / b
except ZeroDivisionError as e:
   print("Caught runtime error:", e)

Following is the output obtained -

Caught runtime error: division by zero

Errors are Raised at Compile Time

Errors occur during the parsing of the code, before the program runs. They consist of syntax errors like missing colons, unmatched brackets, or incorrect indentation, which prevent the code from being executed.

Example: SyntaxError Before Execution

Here, Python raises a SyntaxError because of the missing colon. This happens before execution begins -

# This code will fail to run
if True
   print("Missing colon will cause syntax error")

We get the output as shown below -

File "/home/cg/root/682c9745587be/main.py", line 2
    if True
           ^
SyntaxError: expected ':'

Example: IndentationError Before Execution

The following program never runs because the function body is not properly indented -

# This code also fails before running
def greet():
print("Hello")

The error obtained is as shown below -

File "/home/cg/root/682c9745587be/main.py", line 3
    print("Hello")
    ^
IndentationError: expected an indented block after function definition on line 2