Python – Exceptions:

In this tutorial, we will learn about the handling exceptions in Python. It is quite common that for any program written in any programming language may hit the error during the execution due to any reasons.

Reasons may be the syntactical error, or conditional or operational errors caused due to filesystem or due to the lack required resources to execute the program.

So, we need to handle those kind of exceptions or errors by using different clauses while we do programming.

In Python, we can handle an exception by using the raise exception statement or using the try, except clauses.

Syntax:                                        

try:

raise statement

except x

statement

Exceptions are 2 types:

  1. Pre-defined exceptions:

These are the Exceptions which are existing within the python programming language as Built-in Exceptions. Some of them are arithmetic errors like ZeroDivisionError, FloatingPointError, EOF errors… etc.

  1. User-defined exceptions:

These exceptions are created by programmer which are derived from Exception class

Example of Handling an Exception:

>>> while True:

...     try:

...             x = int(input("Please enter a number: "))

...             print("The number entered is :", x)

...             break

...     except ValueError:

...             print("Sorry !! the given number is not valid number.  Try again...")

...

Output:

Please enter a number: abc

Sorry !! the given number is not valid number.  Try again…

Please enter a number: apple

Sorry !! the given number is not valid number.  Try again…

Please enter a number: a123

Sorry !! the given number is not valid number.  Try again…

Please enter a number: 123

The number entered is : 123

Example by using the Predefined Exception:

>>> try:

...     print(100/0)

... except ZeroDivisionError as error:

...     print(" we Handled predefined error:", error)

...

Output:

we Handled predefined error: division by zero