Top 10 Output Questions on Lists, Functions & Dictionaries – CBSE Class 12 Python

Why Practice These Questions?

Output-based questions on Lists, Functions, and Dictionaries are crucial for scoring high in CBSE Class 12 Computer Science exams. These 10 Python programs are carefully chosen for board-level preparation.

Top 10 Python Output Questions

1. List Copy vs Reference

   def mix(L):
       L2 = L
       L3 = L[:]
       L2.append(100)
       L3.append(200)
       print("L2:", L2)
       print("L3:", L3)
       print("L :", L)
   
   nums = [10, 20, 30]
   mix(nums)
   print(nums)

   Show Answer
   Output:
   L2: [10, 20, 30, 100]
   L3: [10, 20, 30, 200]
   L : [10, 20, 30, 100]
   [10, 20, 30, 100]

   Tip: Assigning L2 = L references the same list, while L3 = L[:] creates a copy.
2. List Mutation in Function

   def tricky(L):
       for i in range(len(L)):
           L[i] = L[i] + sum(L[:i])
       return L
   
   nums = [2, 4, 6, 8]
   print(tricky(nums))

   Show Answer
   Output: [2, 6, 14, 30]
3. Dictionary Key Check

   def fun(d):
       for k in list(d.keys()):
           if k.lower() in 'aeiou':
               d[k] += 1
           else:
               d.pop(k)
       return d
   
   data = {'A': 10, 'B': 20, 'E': 30, 'C': 40}
   print(fun(data))

   Show Answer
   Output: {'A': 11, 'E': 31}
4. List Rotation Mystery

   def mystery(L):
       x = []
       for i in range(len(L)):
           x.append(L[i:] + L[:i])
       return x[-1][1]
   
   lst = [1, 2, 3, 4]
   print(mystery(lst))

   Show Answer
   Output: 1
5. Combine Two Lists into Dictionary

   def combine(L1, L2):
       D = {}
       for i in range(min(len(L1), len(L2))):
           D[L1[i]] = L2[-(i+1)]
       return D
   
   print(combine(['x','y','z'], [1,2,3]))

   Show Answer
   Output: {'x': 3, 'y': 2, 'z': 1}
6. Function Scope vs Mutation

   def modify(L):
       L = L + [50]
       L.append(60)
       print(L)
   
   L = [10, 20, 30]
   modify(L)
   print(L)

   Show Answer
   Output:
   [10, 20, 30, 50, 60]
   [10, 20, 30]
7. Dictionary Update

   def swap_values(D):
       for k in D:
           D[k] = D[k] * 2
       return len(D)
   
   data = {'a':5, 'b':10, 'c':15}
   print(swap_values(data))
   print(data)

   Show Answer
   Output:
   3
   {'a': 10, 'b': 20, 'c': 30}
8. Running Sum of List

   def calc(L):
       for i in range(1, len(L)):
           L[i] += L[i-1]
       return L[-1]
   
   nums = [1,2,3,4]
   print(calc(nums))

   Show Answer
   Output: 10
9. Update Dictionary with Key Check

   def update_dict(D, key, value):
       if key in D:
           D[key] += value
       else:
           D[key] = value
       return D
   
   data = {'A': 10, 'B': 20}
   print(update_dict(data, 'B', 5))
   print(update_dict(data, 'C', 7))

   Show Answer
   Output:
   {'A': 10, 'B': 25}
   {'A': 10, 'B': 25, 'C': 7}
10. Reverse List and Sum

    def rev(L):
        return L[::-1]
    
    def add(L):
        return sum(L)
    
    print(add(rev([1,2,3,4])))

    Show Answer
    Output: 10