Python 25

 Exception Handling

1. Introduction to Errors and Exceptions

 When  a Python program runs, two kinds of problems can occur:

Syntax Errors:

Errors caused by incorrect python syntax

detected before execution

Forex:  x=10

           If x>5     -->missing colon(:)

             print (x);

Exceptions

Errors that occur during execution ,even if syntax is correct 

Print(10/0) //cause zero division error 

2. Types of Errors and Exceptions

Common Built-in Exceptions       Cause                 Example

ZeroDivisionError                   Divide by zero      10/0

ValueError                               Invalid value          int("abc")

TypeError                               Wrong data type      "10" + 5 

NameError                             Variable not defined  print(x)

IndexError                               Invalid index            list[5]

KeyError                                 Missing dictionary key  dict["x"] 

FileNotFoundError                 File not found                 open("a.txt")

3.Exception Handling

  Introduction to try and Except

  Python uses try-except to handle exceptions gracefully 

  Basic Syntax Errors

 try: 

     # Code that may cause an error 

 except:

   # Code that runs if errors occurs 

 Finally: # Optional

   # Code that runs on fail or success 

Example Handling division by  zero

try:

    x = int(input("Enter a number:"))

    print(10/x)

except:

    print("Error: There is some problem in  your code, Zero Divided By")

finally:

    print("completed")

Output:

PS C:\Users\Administrator\Desktop\CCIT\PythonCourse\Day25> python app.py

Enter a number:0

Error: There is some problem in  your code, Zero Divided By

completed

Task2:

try:

    x = "abc"

    y = 5

    m = int(x)

    print (m/y)

except BaseException as e:

    print("Error: There is some problem in  your code:", e)

PS C:\Users\Administrator\Desktop\CCIT\PythonCourse\Day25> python app.py

Error: There is some problem in  your code: invalid literal for int() with base 10: 'abc'

Task3:

try:

    x = "abc"

    y = 5

    m = int(x)

    print (m/y)

except ValueError as e:

    print("Error:Invalid value supplied")

PS C:\Users\Administrator\Desktop\CCIT\PythonCourse\Day25> python app.py

Error:Invalid value supplied

Task4:

try:

    x = 10

    y = 0

    m = int(x)

    print (m/y)

except ValueError as e:

    print("Error:Invalid value supplied")

except ZeroDivisionError:

    print("Wrong Value supplied By", +y)

PS C:\Users\Administrator\Desktop\CCIT\PythonCourse\Day25> python app.py

Wrong Value supplied By 0

Task5:

try:

    x = "abc"

    y = 0

    m = int(x)

    print (m/y)

#except ValueError as e:

 #   print("Error:Invalid value supplied")

except ZeroDivisionError:

    print("Wrong Value supplied By", +y)

except:

     print("Universal Exception block: Wrong Value supplied")

PS C:\Users\Administrator\Desktop\CCIT\PythonCourse\Day25> python app.py

Universal Exception block: Wrong Value supplied

Task6:

try:

    x = "abc"

    y = 0

    m = int(x)

    print (m/y)

#except ValueError as e:

 #   print("Error:Invalid value supplied")

except ZeroDivisionError:

    print("Wrong Value supplied By", +y)

except TypeError:

    print("Wrong Type supplied By")

except:

     print("Universal Exception block: Wrong Value supplied")

finally:

    print("Execution completed")

PS C:\Users\Administrator\Desktop\CCIT\PythonCourse\Day25> python app.py

Universal Exception block: Wrong Value supplied

Execution completed

Exception Hierarchy 

All exceptions inherit from BaseException

BaseException 

   Exception 

           ValueError

            TypeError

            ZeroDivisionError

            FileNotFoundError

--Thanks