We can force raise an exception using the raise keyword. Here is the syntax for calling the “raise” method.
raise [Exception [, args [, traceback]]]
where, the Exception is the name of the exception; the optional “args” represents the value of the exception argument.
The also optional argument, traceback, is the traceback object used for the exception.
#raise_error.py try: i = int ( input ( "Enter a positive integer value: " ) ) if i <= 0: raise ValueError ( "This is not a positive number!!" ) except ValueError as e: print(e)
If we execute the above script at terminal as follows
$python raise_error.py Enter a positive integer: –6
Following is displayed since we have entered a negative number:
This is not a positive number!!
Alternate example code
# Here there is no variable or argument passed with the raised exception
import sys
try:
i = int ( input("Enter a positive integer value: "))
if i <= 0:
raise ValueError#("This is not a positive number!!")
except ValueError as e:
print sys.exc_info()output
Enter a positive integer value: -9 (<type 'exceptions.ValueError'>, ValueError(), <traceback object at 0x0000000003584EC8>)
