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Python Exceptions

·282 words·2 mins·
Programming Python Exceptions Error-Handling Programming
Table of Contents

Python Exceptions
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Exceptions are events that occur during the execution of a program that disrupt the normal flow of instructions. In Python, exceptions are handled using try...except blocks.

Handling Exceptions
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You can use a try...except block to catch and handle exceptions. The code that might raise an exception is placed in the try block, and the code to handle the exception is placed in the except block.

try:
    result = 10 / 0
except ZeroDivisionError:
    print("You can't divide by zero!")

The else and finally Clauses
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You can also include else and finally clauses in a try...except block.

  • The else block is executed if no exceptions are raised in the try block.
  • The finally block is always executed, regardless of whether an exception was raised.
try:
    num = int(input("Enter a number: "))
except ValueError:
    print("That's not a valid number!")
else:
    print(f"You entered {num}")
finally:
    print("Execution complete.")

Raising Exceptions
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You can raise exceptions in your own code using the raise keyword. This is useful when you want to signal that an error has occurred.

def validate_age(age):
    if age < 0:
        raise ValueError("Age cannot be negative")
    return True

try:
    validate_age(-5)
except ValueError as e:
    print(e)  # "Age cannot be negative"

Common Built-in Exceptions
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Python has a number of built-in exceptions that are commonly raised:

  • TypeError: Raised when an operation or function is applied to an object of inappropriate type.
  • ValueError: Raised when a built-in operation or function receives an argument that has the right type but an inappropriate value.
  • IndexError: Raised when a sequence subscript is out of range.
  • KeyError: Raised when a dictionary key is not found.
  • FileNotFoundError: Raised when a file or directory is requested but doesn’t exist.

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