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Solutions for Computer Science, Class 12, CBSE
Assertion (A): Exception handling handles all types of errors and exceptions.
Reasoning (R): Exception handling is responsible for handling anomalous situations during the execution of a program.
Both A and R are true and R is the correct explanation of A.
Explanation
Exception handling in Python allows users to catch and manage various types of errors and exceptions that may occur during program execution. It is designed to handle unexpected or anomalous situations, such as errors or exceptions, that may arise while a program is running.
Assertion (A): Exception handling code is separate from normal code.
Reasoning (R): Program logic is different while exception handling code uses specific keywords to handle exceptions.
Both A and R are true and R is the correct explanation of A.
Explanation
Exception handling code is separate from normal code in programming languages. Exception handling code uses specific constructs like try, except, finally (in Python). Exception handling involves a different flow of control compared to regular program logic. When an exception occurs, the program jumps to the corresponding exception handling block (such as the except block in Python) rather than following the normal sequence of statements.
Assertion (A): Exception handling code is clear and block based in Python.
Reasoning (R): The code where unexpected runtime exception may occur is separate from the code where the action takes place when an exception occurs.
Both A and R are true and R is the correct explanation of A.
Explanation
In Python, the structure of exception handling using clear and distinct blocks like try, except, and finally helps in organizing code. It separates the code where exceptions might occur (within the try block) from the code responsible for handling those exceptions (within the except and finally blocks).
Assertion (A): No matter what exception occurs, you can always make sure that some common action takes place for all types of exceptions.
Reasoning (R): The finally block contains the code that must execute.
Both A and R are true and R is the correct explanation of A.
Explanation
The 'finally' block contains code that must execute, irrespective of whether an exception is raised. This ensures that some common action takes place for all types of exceptions, no matter which exception occurs.
Compile time error
Reason — When a user violates the syntax of a programming language while writing code, it results in a compile-time error. These errors are detected by the compiler during the compilation process and prevent the program from being compiled successfully.
Exception
Reason — An exception is an interrupt or disruption that occurs during the execution of a program. When an exception occurs, it interrupts the normal flow of the program and may cause the program to terminate abruptly if not handled properly.
else
Reason — The 'else' keyword in Python is not specific to exception handling but rather plays a role in conditional statements and control flow structures. On the other hand, in exception handling constructs, the main keywords are 'try,' 'except,' and 'finally.
try
Reason — The try block is a mandatory component of the exception handling process because it encapsulates code that might raise exceptions, allowing them to be caught and handled effectively.
raise
Reason — The raise statement allows the program to force a specified exception to occur at runtime. When a program encounters an abnormal condition during execution, an object of this exception is created and then thrown or raised to the code responsible for catching and handling it.
What all can be the possible outputs of the following code?
def myfunc (x=None) :
result = ""
if x is None:
result = "No argument given"
elif x == 0:
result = "Zero"
elif 0 < x <= 3:
result = "x is between 0 and 3"
else:
result = "x is more than 3"
return result
c = myfunc (3.5)
print (c)
The incorrect indentation of the print
statement will cause an indentation error when the code is executed.
The corrected code is as follows:
def myfunc(x = None) :
result = ""
if x is None:
result = "No argument given"
elif x == 0:
result = "Zero"
elif 0 < x <= 3:
result = "x is between 0 and 3"
else:
result = "x is more than 3"
return result
c = myfunc(3.5)
print(c)
x is more than 3
Working of the code:
The code defines a function myfunc
that takes an argument x
, which defaults to None
. Inside the function, it checks the value of x
using a series of if-elif-else conditions. If x
is None, it sets the result
to "No argument given." If x
is 0, it sets the result
to "Zero." If x
is greater than 0 but less than or equal to 3, it sets the result
to "x is between 0 and 3." Otherwise, if x
is greater than 3, it sets the result
to "x is more than 3." The function then returns the result
. In the provided code, the function is called with the argument 3.5, which falls into the last else condition, resulting in the output "x is more than 3" being stored in variable c
and printed.
(a) IOError — This error is raised if the requested file cannot be opened, or failure of I/O operation.
(b) NameError — This error is raised when an identifier is not found in the local or global namespace.
(c) ValueError — This error is raised when a built-in operation or function receives an argument that has the right type but an inappropriate value.
(d) TypeError — This error is raised when an operation or function is attempted that is invalid for the specified data type.
An Error is a bug in the code that causes irregular output or stops the program from executing whereas an Exception is an irregular unexpected situation occurring during execution on which programmer has no control.
In Python, we can handle exceptions using the try-except block. It includes the following steps:
Here's an example of how to handle an exception:
def divide_numbers(x, y):
try:
result = x / y
except ZeroDivisionError:
print("Error: Division by zero is not allowed.")
else:
print("Division result:", result)
finally:
print("End of division operation.")
divide_numbers(10, 2)
divide_numbers(10, 0)
Division result: 5.0
End of division operation.
Error: Division by zero is not allowed.
End of division operation.
This Python code defines a function divide_numbers
that performs division between two numbers x
and y
. It uses a try-except block to handle exceptions that may arise during division, specifically the ZeroDivisionError. If a division by zero occurs, the program prints an error message indicating that division by zero is not allowed. Otherwise, if the division operation succeeds without any exceptions, it prints the result of the division. The finally block is executed in both cases, indicating the end of the division operation.
The 'finally' clause in a 'try-except' block is executed regardless of whether an exception occurs in the 'try' block or not. Its primary purpose is to ensure that certain actions or cleanup operations are performed, before the program exits or moves on to the next code block.
IOError | IndexError |
---|---|
This error is raised if the file requested cannot be opened, or failure of I/O operation. | This error is raised when an index is not found in a sequence, i.e., out of range or out of bounds. |
Examples of situations that can raise an IOError include: Opening a non-existent file for reading or writing, trying to read from a file that has been closed. | Examples of situations that can raise an IndexError include: Accessing an index that is beyond the length of a list or tuple, trying to access a character in a string at an index that is outside the valid range of indices, using a negative index that is too large for the sequence. |
val = input("Enter a number: ")
try:
pval = int(val)
except ValueError:
print("Error: Conversion to integer failed.")
Enter a number: 23
Enter a number: python
Error: Conversion to integer failed.
In this modified code the input function prompts the user to enter a number. The try block attempts to convert the input value to an integer using int(val)
. If the conversion is successful, pval
will hold the integer value. If the conversion raises a ValueError (e.g., if the input is not a valid integer), the program jumps to the except block and prints an error message indicating that the conversion to an integer failed.
Consider the code given below and fill in the blanks with appropriate error types:
loop = 1
while loop == 1:
try:
a = int(input('Enter the first number: ')
b = int(input('Enter the second number: ')
quotient = a/b
except ...............:
print("Error: Please enter only numbers")
except ...............:
print("\n Error: Second number should not be zero")
except ...............:
print("\n Unsupported operation: Check the date type")
else:
print("Great")
finally:
print("Program execution completed")
loop = int(input('Press 1 to try again !')
continue
loop = 1
while loop == 1:
try:
a = int(input('Enter the first number: '))
b = int(input('Enter the second number: '))
quotient = a / b
except ValueError:
print("Error: Please enter only numbers")
except ZeroDivisionError:
print("\n Error: Second number should not be zero")
except TypeError:
print("\n Unsupported operation: Check the data type")
else:
print("Great")
finally:
print("Program execution completed")
loop = int(input('Press 1 to try again: '))
continue
In the code:
False
Reason — An Error is a bug in the code that causes irregular output or stops the program from executing whereas an Exception is an irregular unexpected situation occurring during execution on which programmer has no control.
True
Reason — Exceptions are caught using the try block because it encapsulates code that might raise exceptions. If any code within the try block causes an error or exception, the program will transfer control to the corresponding except block to handle the exceptional situation.
True
Reason — The order of exception handling in Python is as follows: first, the try block contains the code that may raise an exception. Then, the except block is used to handle specific types of exceptions that may occur within the try block. Finally, the finally block, if present, is executed whether an exception is raised or not.