Sample Paper 1 by Teachoo

Computer Science - Class 11
Teachoo Sample Paper

## ``` print("The sum of all the even numbers in the list is", sum_even(lst)) ```

``` # A function that returns True if a number is even, False otherwise ```

``` def is_even (num): ```

```     return num % 2 == 0   # Missing statement 1 ```

``` # A function that returns the sum of all the even numbers in a list ```

``` def sum_even (lst): ```

```     # Initialize a variable to store the sum ```

```     total = 0 ```

```     # Loop through each element in the list ```

```     for num in lst: ```

```         # Check if the element is even using the is_even function ```

```         if is_even(num)   # Missing statement 2 ```

```             # Add the element to the total ```

```             total += num    # Missing statement 3 ```

```     # Return the total sum ```

```     return total   # Missing statement 4 ```

``` # Take a list of numbers as input from the user ```

``` lst = list(map(int, input( "Enter a list of numbers: " ).split())) ```

``` # Print the sum of all the even numbers in the list using the sum_even function ```

``` print( "The sum of all the even numbers in the list is" , sum_even(lst)) ```

• The question requires us to write two functions: one that checks if a number is even, and another that sums up all the even numbers in a list.
• The first function, is_even , takes a parameter num which is a number. It returns True if num is divisible by 2, and False otherwise. To check if a number is divisible by 2, we can use the modulo operator ( % ) which gives the remainder of the division. If the remainder is 0, then the number is divisible by 2. So, we can write:

``` def is_even(num): ```

```      return num % 2 == 0 ```

• This is the missing statement 1 in the code.
• The second function, sum_even , takes a parameter lst which is a list of numbers. It returns the sum of all the even numbers in the list. To do this, we need to do the following steps:
• Initialize a variable total to store the sum. We can start with 0 as the initial value.
• Loop through each element in the list using a for loop. We can use the variable num to refer to each element.
• Check if the element is even using the is_even function. If it is, then add it to the total variable using the assignment operator ( += ) which adds and assigns the value in one step.
• Return the total variable after the loop ends.
• So, we can write:

``` def sum_even(lst): ```

```     # Initialize a variable to store the sum ```

```     total = 0 ```

```     # Loop through each element in the list ```

```     for num in lst: ```

```         # Check if the element is even using the is_even function ```

```         if is_even(num): ```

```             # Add the element to the total ```

```              total += num ```

```     # Return the total sum ```

```      return total ```

• These are the missing statements 2, 3 and 4 in the code.
• The last part of the code takes a list of numbers as input from the user and prints the sum of all the even numbers in it using the sum_even function. To do this, we need to do the following steps:
• Use the input function to get a string from the user. We can pass a prompt message as an argument to this function.
• Use the split method to split the string into a list of substrings based on whitespace characters (such as space, tab, newline, etc.). For example, "1 2 3".split() will give ["1", "2", "3"] .
• Use the map function to apply another function (such as int ) to each element in a list and return a new list with those values. For example, map(int, ["1", "2", "3"]) will give [1, 2, 3] .
• Use the list function to convert any iterable (such as a map object) into a list. For example, list(map(int, ["1", "2", "3"])) will give [1, 2, 3] .
• Assign this list to a variable named lst .
• Use the print function to display a message and the result of calling sum_even on lst . We can use commas to separate multiple arguments to this function.

So, the final code is:

``` # A function that returns True if a number is even, False otherwise ```

``` def is_even (num): ```

```     return num % 2 == 0 ```

``` # A function that returns the sum of all the even numbers in a list ```

``` def sum_even (lst): ```

```     # Initialize a variable to store the sum ```

```     total = 0 ```

```     # Loop through each element in the list ```

```     for num in lst: ```

```         # Check if the element is even using the is_even function ```

```         if is_even(num): ```

```             # Add the element to the total ```

```             total += num ```

```     # Return the total sum ```

```     return total ```

``` # Take a list of numbers as input from the user ```

``` lst = list(map(int, input( "Enter a list of numbers: " ).split())) ```

``` # Print the sum of all the even numbers in the list using the sum_even function ```

``` print("The sum of all the even numbers in the list is", sum_even(lst)) ```