Question 22 - CBSE Class 12 Sample Paper for 2024 Boards - Solutions to CBSE Sample Paper - Computer Science Class 12

Predict the output of the following code:

Answer

Answer by student

The output of the following code is:

4*L

33*4

21*S

10*6

Detailed answer by teachoo

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To predict the output of the code, we need to understand the following concepts:

• Strings are sequences of characters enclosed in quotes. For example, S=“LOST” is a string of four characters. We can access the individual characters of a string by using indexing , which starts from 0. For example, S[0] is “L”, S[1] is “O”, and so on.
• Lists are collections of values that can be of different types. For example, L=[10,21,33,4] is a list of four integers. We can also access the elements of a list by using indexing, similar to strings. For example, L[0] is 10, L[1] is 21, and so on.
• Dictionaries are collections of key-value pairs that are enclosed in curly braces. For example, D={} is an empty dictionary. We can add key-value pairs to a dictionary by using the syntax D[key]=value. For example, D[4]=“L” adds a key-value pair where 4 is the key and “L” is the value. We can access the value associated with a key by using D[key]. For example, D[4] returns “L”.
• len() is a built-in function that returns the length of a sequence, such as a string or a list. For example, len(S) returns 4 and len(L) returns 4.
• range() is a built-in function that returns a sequence of numbers from 0 to a specified number (exclusive). For example, range(4) returns 0, 1, 2, 3.
• for loops are used to iterate over a sequence and execute a block of code for each element. For example, for I in range(4): print(I) prints 0, 1, 2, 3 on separate lines.
• if statements are used to check a condition and execute a block of code if the condition is true. For example, if I%2==0: print(“even”) prints “even” if I is divisible by 2.
• pop() is a method that removes and returns the last element of a list. For example, L.pop() returns 4 and modifies L to [10,21,33].
• items() is a method that returns a view object that contains the key-value pairs of a dictionary as tuples. For example, D.items() returns [(4,“L”),(33,“4”),(21,“S”),(10,“T”)].
• print() is a built-in function that prints the given arguments to the standard output. For example, print(K,V) prints the values of K and V separated by a space. We can use the sep parameter to specify a different separator. For example, print(K,V,sep=“*”) prints the values of K and V separated by an asterisk.

Now that we have understood the concepts, let us go through the code line by line and see what it does:

• Line 1: S=“LOST” assigns the string “LOST” to the variable S.
• Line 2: L=[10,21,33,4] assigns the list [10,21,33,4] to the variable L.
• Line 3: D={} assigns an empty dictionary to the variable D.
• Line 4: for I in range(len(S)): starts a for loop that iterates over the range(4), which is 0, 1, 2, 3. The variable I takes each value in turn.
• Line 5: if I%2==0: checks if I is divisible by 2 (even). If yes, it executes line 6. If no, it executes line 8.
• Line 6: D[L.pop()]=S[I] adds a key-value pair to D where the key is L.pop() and the value is S[I]. This means that it removes and returns the last element of L and assigns it as the key (4), and accesses and returns the element of S at index I (0) and assigns it as the value (“L”). So D becomes {4:“L”} and L becomes [10,21,33].
• Line 7: I becomes 1 and the loop continues.
• Line 8: D[L.pop()]=I+3 adds a key-value pair to D where the key is L.pop() and the value is I+1. This means that it removes and returns the last element of L and assigns it as the key (33), and adds 3 to I (1) and assigns it as the value (4). So D becomes {4:“L”, 33:4} and L becomes [10,21].
• Line 9: I becomes 2 and the loop continues.
• Line 6: D[L.pop()]=S[I] adds a key-value pair to D where the key is L.pop() and the value is S[I]. This means that it removes and returns the last element of L and assigns it as the key (21), and accesses and returns the element of S at index I (2) and assigns it as the value (“S”). So D becomes {4:“L”, 33:4, 21:“S”} and L becomes [10].
• Line 7: I becomes 3 and the loop ends.
• Line 10: for K,V in D.items(): starts another for loop that iterates over D.items(), which is [(4,“L”),(33,4),(21,“S”),(10,“T”)]. The variables K and V take each tuple in turn.
• Line 11: print(K,V,sep=" ") prints the values of K and V separated by an asterisk. For example, when K is 4 and V is “L”, it prints 4 L.

Therefore, the output of the code is:

4*L

33*4

21*S

10*6

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