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Error and Exception in Python

23rd May 2023

Python uses errors and exceptions to deal with extraordinary circumstances that could arise while a programme is being executed. The usual flow of the programme is interrupted when an error or exception occurs, and Python raises an error or exception object to specify the error’s kind and specifics. Try-except blocks can be used to handle these mistakes and exceptions. Here is an illustration of how Python handles errors and exceptions:

# Example 1: Handling a specific exception

try:
    num1 = int(input("Enter a number: "))
    num2 = int(input("Enter another number: "))
    result = num1 / num2
    print("Result:", result)
except ZeroDivisionError:
    print("Error: Division by zero is not allowed.")

# Example 2: Handling multiple exceptions

try:
    num = int(input("Enter a number: "))
    result = 100 / num
    print("Result:", result)
except ValueError:
    print("Error: Invalid input. Please enter a valid number.")
except ZeroDivisionError:
    print("Error: Division by zero is not allowed.")

# Example 3: Handling any exception (generic exception)

try:
    file = open("nonexistent_file.txt", "r")
    content = file.read()
    file.close()
    print("Content:", content)
except Exception as e:
    print("Error:", str(e))

In the first example, a ,ZeroDivisionError, exception is handled if the user enters zero as the second number for division. In the second example, both 'ValueError‘ and ‘ZeroDivisionError' exceptions are handled, depending on the user’s input. In the third example, a generic ‘Exception‘ is caught, which can handle any type of exception. The 'as' keyword allows you to access the exception object, which can be useful for printing error messages or retrieving specific information about the error.

Build-in exception in python

23rd May 2023

When certain faults or extraordinary circumstances arise during the execution of a programme, built-in exceptions in the Python programming language can be raised (or thrown). These exceptions, which are defined in the Python standard library, can be applied to deal with particular error kinds.

1.TypeError: Raised when an operation or function is applied to an object of inappropriate type.

# Example: TypeError
x = 10
y = '5'
z = x + y  # Raises TypeError: unsupported operand type(s) for +: 'int' and 'str'

2. ValueError: Raised when a function receives an argument of the correct type but an inappropriate value.

# Example: ValueError
age = input("Enter your age: ")
age = int(age)  # Raises ValueError if the input cannot be converted to an integer

3. IndexError: Raised when a sequence subscript is out of range.

# Example: IndexError
numbers = [1, 2, 3]
print(numbers[3])  # Raises IndexError: list index out of range

4. KeyError: Raised when a dictionary key is not found.

# Example: KeyError
person = {'name': 'John', 'age': 30}
print(person['gender'])  # Raises KeyError: 'gender'

5. FileNotFoundError: Raised when a file or directory is requested but cannot be found.

# Example: FileNotFoundError
file_path = 'path/to/nonexistent/file.txt'
with open(file_path, 'r') as file:  # Raises FileNotFoundError
    content = file.read()

6. ZeroDivisionError: Raised when division or modulo operation is performed with zero as the divisor.

# Example: ZeroDivisionError
x = 10
y = 0
result = x / y  # Raises ZeroDivisionError: division by zero

7. ZeroDivisionError: Raised when division or modulo operation is performed with zero as the divisor.

8. ImportError: Raised when an import statement fails to find and load a module.

9. AssertionError: Raised when an assert statement fails.

10. StopIteration: Raised to signal the end of an iterator.

These are just a few examples of built-in exceptions in Python. You can also create your own custom exceptions by deriving from the base Exception class or any other built-in exception class.