Dictionary Flashcards
every topic from dictionary ad all functions
What is a dictionary in Python?
A dictionary is a sequence data type.
It is mutable, meaning it can be changed after creation.
It is denoted by curly braces {}.
Dictionaries store data in key-value pairs.
Keys in a dictionary are unique.
Example: D = {1: 10, 2: 20, 3: 30}
How do you access values in a dictionary?
Use the syntax: Dict_Name[key_name]
D = {1: 10, 2: 20, 3: 30}
D[1] # Output: 10
D[2] # Output: 20
If a key is duplicated, the last assigned value is stored
D = {1: 10, 2: 20, 3: 30, 1: 40}
D # Output: {1: 40, 2: 20, 3: 30}
How do you update a value in a dictionary?
Use the syntax: Dict_Name[Key_Name] = New_Value
D = {‘A’: 10, ‘B’: 20, ‘C’: 30}
D[‘A’] = 15 # Update value of key ‘A’
D # Output: {‘A’: 15, ‘B’: 20, ‘C’: 30}
How do you add a new item to a dictionary?
Use the syntax: Dict_Name[New_Key_Name] = Value
D = {1: 10, 2: 20, 3: 30}
D[4] = 40 # Add new key-value pair
D # Output: {1: 10, 2: 20, 3: 30, 4: 40}
How do you loop through a dictionary?
Use keys(), values(), or items() methods.
keys(): Returns the keys of the dictionary.
D = {1: 10, 2: 20, 3: 30}
for key in D.keys():
print(key) # Output: 1, 2, 3
values(): Returns the values of the dictionary.
for value in D.values():
print(value) # Output: 10, 20, 30
items(): Returns key-value pairs as tuples.
for item in D.items():
print(item) # Output: (1, 10), (2, 20), (3, 30)
What does the len() function do in a dictionary?
Returns the number of keys in the dictionary
D = {1: 10, 2: 20, 3: 30}
len(D) # Output: 3
What does the dict() function do?
Used to create a dictionary.
D = dict(name=”Shiva”, age=26, country=”India”)
D # Output: {‘name’: ‘S
What does the get() method do?
Returns the value of the specified key.
D = {1: 10, 2: 20, 3: 30}
D.get(1) # Output: 10
D.get(3) # Output: 30
What does the update() method do?
Inserts new key-value pairs or merges two dictionaries.
D = {1: 10, 2: 20, 3: 30}
D.update({4: 40}) # Add new key-value pair
D
What does the del keyword do?
Used to delete an element from the dictionary using the key.
D = {1: 10, 2: 20, 3: 30}
del D[1] # Delete key 1
D # Output: {2: 20,
What does the clear() method do?
Deletes all elements from the dictionary but retains the structure
D = {1: 10, 2: 20, 3: 30}
D.clear()
D # Output: {}
What does the pop() method do?
Deletes a specific element and returns its value.
D = {1: 10, 2: 20, 3: 30}
D.pop(2) # Output: 20
D # Output: {1: 10, 3:
What does the popitem() method do?
Deletes the last element and returns it as a key-value pair.
D = {1: 10, 2: 20, 3: 30}
D.popitem() # Output: (3, 30)
D # Output: {1
What does the setdefault() method do?
Returns the value of a key. If the key doesn’t exist, it adds the key with a specified value.
D = {1: 10, 2: 20, 3: 30}
D.setdefault(4, 40) # Output: 40
D # Output:
What does the max() function do?
Returns the largest key in the dictionary (based on ASCII values for strings).
D = {1: 10, 2: 20, 3: 30}
max(D) # Output: 3
What does the min() function do?
Returns the smallest key in the dictionary (based on ASCII values for strings)
D = {1: 10, 2: 20, 3: 30}
min(D) # Output: 1
What does the fromkeys() method do?
Creates a dictionary with multiple keys having the same value.
K = {‘A’, ‘B’, ‘C’}
V = 10
D = dict.fromkeys(K, V)
D # Output: {‘A’: 10
What does the copy() method do?
Returns a copy of the dictionary
D = {1: 10, 2: 20}
D1 = D.copy()
D1 # Output: {1: 10, 2: 20}
What does the sorted() function do?
Sorts the keys, values, or items of the dictionary.
D = {1: 10, 4: 40, 3: 30, 2: 20}
sorted(D) # Output: [1, 2, 3, 4]
sorte
Write a program to count the frequency of characters in a string using a dictionary.
S = input(“Enter a string: “)
D = {}
for c in S:
if c in D:
D[c] += 1
else:
D[c] = 1
print(“Frequency of Characters:”, D)
