Python Dictionary MCQs with Answers

Question. Which of the following statements create a dictionary?
(a) d = {}
(b) d = {“john”:40, “peter”:45}
(c) d = {40:”john”, 45:”peter”}
(d) All of the mentioned
Answer: d
Explanation: Dictionaries are created by specifying keys and values.

Question. What will be the output of the following Python code snippet?
1. d = {"john":40, "peter":45}
(a) “john”, 40, 45, and “peter”
(b) “john” and “peter”
(c) 40 and 45
(d) d = (40:”john”, 45:”peter”)
Answer: b
Explanation: Dictionaries appear in the form of keys and values.

Question. What will be the output of the following Python code snippet?
1. d = {"john":40, "peter":45}
2. "john" in d
(a) True
(b) False
(c) None
(d) Error
Answer: a
Explanation: In can be used to check if the key is int dictionary.

Question. What will be the output of the following Python code snippet?
1. d1 = {"john":40, "peter":45}
2. d2 = {"john":466, "peter":45}
3. d1 == d2
(a) True
(b) False
(c) None
(d) Error
Answer: b
Explanation: If d2 was initialized as d2 = d1 the answer would be true.

Question. What will be the output of the following Python code snippet?
1. d1 = {"john":40, "peter":45}
2. d2 = {"john":466, "peter":45}
3. \( d1 > d2 \)
(a) True
(b) False
(c) Error
(d) None
Answer: c
Explanation: Arithmetic \( > \) operator cannot be used with dictionaries.

Question. What will be the output of the following Python code snippet?
1. d = {"john":40, "peter":45}
2. d["john"]
(a) 40
(b) 45
(c) “john”
(d) “peter”
Answer: a
Explanation: Execute in the shell to verify.

Question. Suppose d = {“john”:40, “peter”:45}, to delete the entry for “john” what command do we use?
(a) d.delete(“john”:40)
(b) d.delete(“john”)
(c) del d[“john”]
(d) del d(“john”:40)
Answer: c
Explanation: Execute in the shell to verify.

Question. Suppose d = {“john”:40, “peter”:45}. To obtain the number of entries in dictionary which command do we use?
(a) d.size()
(b) len(d)
(c) size(d)
(d) d.len()
Answer: b
Explanation: Execute in the shell to verify.

Question. What will be the output of the following Python code snippet?
1. d = {"john":40, "peter":45}
2. print(list(d.keys()))
(a) [“john”, “peter”]
(b) [“john”:40, “peter”:45]
(c) (“john”, “peter”)
(d) (“john”:40, “peter”:45)
Answer: a
Explanation: The output of the code shown above is a list containing only keys of the dictionary d, in the form of a list.

Question. Suppose d = {“john”:40, “peter”:45}, what happens when we try to retrieve a value using the expression d[“susan”]?
(a) Since “susan” is not a value in the set, Python raises a KeyError exception
(b) It is executed fine and no exception is raised, and it returns None
(c) Since “susan” is not a key in the set, Python raises a KeyError exception
(d) Since “susan” is not a key in the set, Python raises a syntax error
Answer: c
Explanation: Execute in the shell to verify.

Question. Which of these about a dictionary is false?
(a) The values of a dictionary can be accessed using keys
(b) The keys of a dictionary can be accessed using values
(c) Dictionaries aren’t ordered
(d) Dictionaries are mutable
Answer: b
Explanation: The values of a dictionary can be accessed using keys but the keys of a dictionary can’t be accessed using values.

Question. Which of the following is not a declaration of the dictionary?
(a) {1: ‘A’, 2: ‘B’}
(b) dict([[1,”A”],[2,”B”]])
(c) {1,”A”,2”B”}
(d) { }
Answer: c
Explanation: Option c is a set, not a dictionary.

Question. What will be the output of the following Python code snippet?
a={1:"A",2:"B",3:"C"}
for i,j in a.items():
 print(i,j,end=" ")
(a) 1 A 2 B 3 C
(b) 1 2 3
(c) A B C
(d) 1:”A” 2:”B” 3:”C”
Answer: a
Explanation: In the above code, variables i and j iterate over the keys and values of the dictionary respectively.

Question. What will be the output of the following Python code snippet?
a={1:"A",2:"B",3:"C"}
print(a.get(1,4))
(a) 1
(b) A
(c) 4
(d) Invalid syntax for get method
Answer: b
Explanation: The get() method returns the value of the key if the key is present in the dictionary and the default value(second parameter) if the key isn’t present in the dictionary.

Question. What will be the output of the following Python code snippet?
a={1:"A",2:"B",3:"C"}
print(a.get(5,4))
(a) Error, invalid syntax
(b) A
(c) 5
(d) 4
Answer: d
Explanation: The get() method returns the default value(second parameter) if the key isn’t present in the dictionary.

Question. What will be the output of the following Python code snippet?
a={1:"A",2:"B",3:"C"}
print(a.setdefault(3))
(a) {1: ‘A’, 2: ‘B’, 3: ‘C’}
(b) C
(c) {1: 3, 2: 3, 3: 3}
(d) No method called setdefault() exists for dictionary
Answer: b
Explanation: setdefault() is similar to get() but will set dict[key]=default if key is not already in the dictionary.

Question. What will be the output of the following Python code snippet?
a={1:"A",2:"B",3:"C"}
a.setdefault(4,"D")
print(a)
(a) {1: ‘A’, 2: ‘B’, 3: ‘C’, 4: ‘D’}
(b) None
(c) Error
(d) [1,3,6,10]
Answer: a
Explanation: setdefault() will set dict[key]=default if key is not already in the dictionary.

Question. What will be the output of the following Python code?
a={1:"A",2:"B",3:"C"}
b={4:"D",5:"E"}
a.update(b)
print(a)
(a) {1: ‘A’, 2: ‘B’, 3: ‘C’}
(b) Method update() doesn’t exist for dictionaries
(c) {1: ‘A’, 2: ‘B’, 3: ‘C’, 4: ‘D’, 5: ‘E’}
(d) {4: ‘D’, 5: ‘E’}
Answer: c
Explanation: update() method adds dictionary b’s key-value pairs to dictionary a. Execute in python shell to verify.

Question. What will be the output of the following Python code?
a={1:"A",2:"B",3:"C"}
b=a.copy()
b[2]="D"
print(a)
(a) Error, copy() method doesn’t exist for dictionaries
(b) {1: ‘A’, 2: ‘B’, 3: ‘C’}
(c) {1: ‘A’, 2: ‘D’, 3: ‘C’}
(d) “None” is printed
Answer: b
Explanation: Changes made in the copy of the dictionary isn’t reflected in the original one.

Question. What will be the output of the following Python code?
a={1:"A",2:"B",3:"C"}
a.clear()
print(a)
(a) None
(b) { None:None, None:None, None:None}
(c) {1:None, 2:None, 3:None}
(d) { }
Answer: d
Explanation: The clear() method clears all the key-value pairs in the dictionary.

Question. Which of the following isn’t true about dictionary keys?
(a) More than one key isn’t allowed
(b) Keys must be immutable
(c) Keys must be integers
(d) When duplicate keys encountered, the last assignment wins
Answer: c
Explanation: Keys of a dictionary may be any data type that is immutable.

Question. What will be the output of the following Python code?
a={1:5,2:3,3:4}
a.pop(3)
print(a)
(a) {1: 5}
(b) {1: 5, 2: 3}
(c) Error, syntax error for pop() method
(d) {1: 5, 3: 4}
Answer: b
Explanation: pop() method removes the key-value pair for the key mentioned in the pop() method.

Question. What will be the output of the following Python code?
a={1:5,2:3,3:4}
print(a.pop(4,9))
(a) 9
(b) 3
(c) Too many arguments for pop() method
(d) 4
Answer: a
Explanation: pop() method returns the value when the key is passed as an argument and otherwise returns the default value(second argument) if the key isn’t present in the dictionary.

Question. What will be the output of the following Python code?
a={1:"A",2:"B",3:"C"}
for i in a:
 print(i,end=" ")
(a) 1 2 3
(b) ‘A’ ‘B’ ‘C’
(c) 1 ‘A’ 2 ‘B’ 3 ‘C’
(d) Error, it should be: for i in a.items():
Answer: a
Explanation: The variable i iterates over the keys of the dictionary and hence the keys are printed.

Question. What will be the output of the following Python code?
>>> a={1:"A",2:"B",3:"C"}
>>> a.items()
(a) Syntax error
(b) dict_items([(‘A’), (‘B’), (‘C’)])
(c) dict_items([(1,2,3)])
(d) dict_items([(1, ‘A’), (2, ‘B’), (3, ‘C’)])
Answer: d
Explanation: The method items() returns list of tuples with each tuple having a key value pair.

Question. Which of the statements about dictionary values if false?
(a) More than one key can have the same value
(b) The values of the dictionary can be accessed as dict[key]
(c) Values of a dictionary must be unique
(d) Values of a dictionary can be a mixture of letters and numbers
Answer: c
Explanation: More than one key can have the same value.

Question. What will be the output of the following Python code snippet?
>>> a={1:"A",2:"B",3:"C"}
>>> del a
(a) method del doesn’t exist for the dictionary
(b) del deletes the values in the dictionary
(c) del deletes the entire dictionary
(d) del deletes the keys in the dictionary
Answer: c
Explanation: del deletes the entire dictionary and any further attempt to access it will throw an error.

Question. If a is a dictionary with some key-value pairs, what does a.popitem() do?
(a) Removes an arbitrary element
(b) Removes all the key-value pairs
(c) Removes the key-value pair for the key given as an argument
(d) Invalid method for dictionary
Answer: a
Explanation: The method popitem() removes a random key-value pair.

Question. What will be the output of the following Python code snippet?
total={}
def insert(items):
 if items in total:
 total[items] += 1
 else:
 total[items] = 1
insert('Apple')
insert('Ball')
insert('Apple')
print (len(total))
(a) 3
(b) 1
(c) 2
(d) 0
Answer: c
Explanation: The insert() function counts the number of occurrences of the item being inserted into the dictionary. There are only 2 keys present since the key ‘Apple’ is repeated. Thus, the length of the dictionary is 2.

Question. What will be the output of the following Python code snippet?
a = {}
a[1] = 1
a['1'] = 2
a[1]=a[1]+1
count = 0
for i in a:
 count += a[i]
print(count)
(a) 1
(b) 2
(c) 4
(d) Error, the keys can’t be a mixture of letters and numbers
Answer: c
Explanation: The above piece of code basically finds the sum of the values of keys.

Question. What will be the output of the following Python code snippet?
numbers = {}
letters = {}
comb = {}
numbers[1] = 56
numbers[3] = 7
letters[4] = 'B'
comb['Numbers'] = numbers
comb['Letters'] = letters
print(comb)
(a) Error, dictionary in a dictionary can’t exist
(b) ‘Numbers’: {1: 56, 3: 7}
(c) {‘Numbers’: {1: 56}, ‘Letters’: {4: ‘B’}}
(d) {‘Numbers’: {1: 56, 3: 7}, ‘Letters’: {4: ‘B’}}
Answer: d
Explanation: Dictionary in a dictionary can exist.

Question. What will be the output of the following Python code snippet?
test = {1:'A', 2:'B', 3:'C'}
test = {}
print(len(test))
(a) 0
(b) None
(c) 3
(d) An exception is thrown
Answer: a
Explanation: In the second line of code, the dictionary becomes an empty dictionary. Thus, length=0.

Question. What will be the output of the following Python code snippet?
test = {1:'A', 2:'B', 3:'C'}
del test[1]
test[1] = 'D'
del test[2]
print(len(test))
(a) 0
(b) 2
(c) Error as the key-value pair of 1:’A’ is already deleted
(d) 1
Answer: b
Explanation: After the key-value pair of 1:’A’ is deleted, the key-value pair of 1:’D’ is added.

Question. What will be the output of the following Python code snippet?
a = {}
a[1] = 1
a['1'] = 2
a[1.0]=4
count = 0
for i in a:
 count += a[i]
print(count)
(a) An exception is thrown
(b) 3
(c) 6
(d) 2
Answer: c
Explanation: The value of key 1 is 4 since 1 and 1.0 are the same. Then, the function count() gives the sum of all the values of the keys (2+4).

Question. What will be the output of the following Python code snippet?
a={}
a['a']=1
a['b']=[2,3,4]
print(a)
(a) Exception is thrown
(b) {‘b’: [2], ‘a’: 1}
(c) {‘b’: [2], ‘a’: [3]}
(d) {‘b’: [2, 3, 4], ‘a’: 1}
Answer: d
Explanation: Mutable members can be used as the values of the dictionary but they cannot be used as the keys of the dictionary.

Question. What will be the output of the following Python code snippet?
>>>import collections
>>> a=collections.Counter([1,1,2,3,3,4,4,4])
>>> a
(a) {1,2,3,4}
(b) Counter({4, 1, 3, 2})
(c) Counter({4: 3, 1: 2, 3: 2, 2: 1})
(d) {4: 3, 1: 2, 3: 2, 2: 1}
Answer: c
Explanation: The statement a=collections.OrderedDict() generates a dictionary with the number as the key and the count of times the number appears as the value.

Question. What will be the output of the following Python code snippet?
>>>import collections
>>> b=collections.Counter([2,2,3,4,4,4])
>>> b.most_common(1)
(a) Counter({4: 3, 2: 2, 3: 1})
(b) {3:1}
(c) {4:3}
(d) [(4, 3)]
Answer: d
Explanation: The most_common() method returns the n number key-value pairs where the value is the most recurring.

Question. What will be the output of the following Python code snippet?
>>>import collections
>>> b=collections.Counter([2,2,3,4,4,4])
>>> b.most_common(1)
(a) Counter({4: 3, 2: 2, 3: 1})
(b) {3:1}
(c) {4:3}
(d) [(4, 3)]
Answer: d
Explanation: The most_common() method returns the n number key-value pairs where the value is the most recurring.

Question. What will be the output of the following Python code snippet?
>>> import collections
>>> a=collections.Counter([2,2,3,3,3,4])
>>> b=collections.Counter([2,2,3,4,4])
>>> a|b
(a) Counter({3: 3, 2: 2, 4: 2})
(b) Counter({2: 2, 3: 1, 4: 1})
(c) Counter({3: 2})
(d) Counter({4: 1})
Answer: a
Explanation: a|b returns the pair of keys and the highest recurring value.

Question. What will be the output of the following Python code snippet?
>>> import collections
>>> a=collections.Counter([3,3,4,5])
>>> b=collections.Counter([3,4,4,5,5,5])
>>> a&b
(a) Counter({3: 12, 4: 1, 5: 1})
(b) Counter({3: 1, 4: 1, 5: 1})
(c) Counter({4: 2})
(d) Counter({5: 1})
Answer: b
Explanation: a&b returns the pair of keys and the lowest recurring value.

Question. The following Python code is invalid.
class demo(dict):
 def __test__(self,key):
 return []
a = demo()
a['test'] = 7
print(a)
(a) True
(b) False
Answer: b
Explanation: The output of the code is: {‘test’:7}.

Question. What will be the output of the following Python code?
count={}
count[(1,2,4)] = 5
count[(4,2,1)] = 7
count[(1,2)] = 6
count[(4,2,1)] = 2
tot = 0
for i in count:
 tot=tot+count[i]
print(len(count)+tot)
(a) 25
(b) 17
(c) 16
(d) Tuples can’t be made keys of a dictionary
Answer: c
Explanation: Tuples can be made keys of a dictionary. Length of the dictionary is 3 as the value of the key (4,2,1) is modified to 2. The value of the variable tot is 5+6+2=13.

Question. What will be the output of the following Python code?
a={}
a[2]=1
a[1]=[2,3,4]
print(a[1][1])
(a) [2,3,4]
(b) 3
(c) 2
(d) An exception is thrown
Answer: b
Explanation: Now, a={1:[2,3,4],2:1} . a[1][1] refers to second element having key 1.

Question. What will be the output of the following Python code?
>>> a={'B':5,'A':9,'C':7}
>>> sorted(a)
(a) [‘A’,’B’,’C’]
(b) [‘B’,’C’,’A’]
(c) [5,7,9]
(d) [9,5,7]
Answer: a
Explanation: Return a new sorted list of keys in the dictionary.

Question. What will be the output of the following Python code?
>>> a={i: i*i for i in range(6)}
>>> a
(a) Dictionary comprehension doesn’t exist
(b) {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6:36}
(c) {0: 0, 1: 1, 4: 4, 9: 9, 16: 16, 25: 25}
(d) {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
Answer: d
Explanation: Dictionary comprehension is implemented in the above piece of code.

Question. What will be the output of the following Python code?
>>> a={}
>>> a.fromkeys([1,2,3],"check")
(a) Syntax error
(b) {1:”check”,2:”check”,3:”check”}
(c) “check”
(d) {1:None,2:None,3:None}
Answer: b
Explanation: The dictionary takes values of keys from the list and initializes it to the default value (value given in the second parameter). Execute in Python shell to verify.

Question. What will be the output of the following Python code?
>>> b={}
>>> all(b)
(a) { }
(b) False
(c) True
(d) An exception is thrown
Answer: c
Explanation: Function all() returns True if all keys of the dictionary are true or if the dictionary is empty.

Question. If b is a dictionary, what does any(b) do?
(a) Returns True if any key of the dictionary is true
(b) Returns False if dictionary is empty
(c) Returns True if all keys of the dictionary are true
(d) Method any() doesn’t exist for dictionary
Answer: a
Explanation: Method any() returns True if any key of the dictionary is true and False if the dictionary is empty.

Question. What will be the output of the following Python code?
>>> a={"a":1,"b":2,"c":3}
>>> b=dict(zip(a.values(),a.keys()))
>>> b
(a) {‘a’: 1, ‘b’: 2, ‘c’: 3}
(b) An exception is thrown
(c) {‘a’: ‘b’: ‘c’: }
(d) {1: ‘a’, 2: ‘b’, 3: ‘c’}
Answer: d
Explanation: The above piece of code inverts the key-value pairs in the dictionary.

Question. What will be the output of the following Python code?
>>> a={i: 'A' + str(i) for i in range(5)}
>>> a
(a) An exception is thrown
(b) {0: ‘A0’, 1: ‘A1’, 2: ‘A2’, 3: ‘A3’, 4: ‘A4’}
(c) {0: ‘A’, 1: ‘A’, 2: ‘A’, 3: ‘A’, 4: ‘A’}
(d) {0: ‘0’, 1: ‘1’, 2: ‘2’, 3: ‘3’, 4: ‘4’}
Answer: b
Explanation: Dictionary comprehension and string concatenation is implemented in the above piece of code.

Question. What will be the output of the following Python code?
>>> a=dict()
>>> a[1]
(a) An exception is thrown since the dictionary is empty
(b) ‘ ‘
(c) 1
(d) 0
Answer: a
Explanation: The values of a dictionary can be accessed through the keys only if the keys exist in the dictionary.

Question. What will be the output of the following Python code?
>>> import collections
>>> a=dict()
>>> a=collections.defaultdict(int)
>>> a[1]
(a) 1
(b) 0
(c) An exception is thrown
(d) ‘ ‘
Answer: b
Explanation: The statement a=collections.defaultdict(int) gives the default value of 0 (since int data type is given within the parenthesis) even if the keys don’t exist in the dictionary.

Question. What will be the output of the following Python code?
>>> import collections
>>> a=dict()
>>> a=collections.defaultdict(str)
>>> a['A']
(a) An exception is thrown since the dictionary is empty
(b) ‘ ‘
(c) ‘A’
(d) 0
Answer: b
Explanation: The statement a=collections.defaultdict(str) gives the default value of ‘ ‘ even if the keys don’t exist in the dictionary.

Question. What will be the output of the following Python code?
>>> import collections
>>> b=dict()
>>> b=collections.defaultdict(lambda: 7)
>>> b[4]
(a) 4
(b) 0
(c) An exception is thrown
(d) 7
Answer: d
Explanation: The statement a=collections.defaultdict(lambda: x) gives the default value of x even if the keys don’t exist in the dictionary.

Question. What will be the output of the following Python code?
>>> import collections
>>> a=collections.OrderedDict((str(x),x) for x in range(3))
>>> a
(a) {‘2’:2, ‘0’:0, ‘1’:1}
(b) OrderedDict([(‘0’, 0), (‘1’, 1), (‘2’, 2)])
(c) An exception is thrown
(d) ‘ ‘
Answer: b
Explanation: The line of code a=collections.OrderedDict() generates a dictionary satisfying the conditions given within the parenthesis and in an ascending order of the keys.