Creating a dictionary:
# This creates a dictionary with keys 'a' and 'b' and values 1 and 2
my_dict = {'a': 1, 'b': 2}
# This creates an empty dictionary
empty_dict = {}
Accessing elements of a dictionary:
# This will print the value for key 'a'
print(my_dict['a'])
# This will print the value for key 'b'
print(my_dict.get('b'))
# This will print all the keys in the dictionary
print(my_dict.keys())
# This will print all the values in the dictionary
print(my_dict.values())
Modifying elements of a dictionary:
# This will add a new key-value pair to the dictionary my_dict['c'] = 3 # This will update the value for key 'b' my_dict['b'] = 4 # This will remove the key-value pair for key 'a' del my_dict['a']
Iterating over a dictionary:
# This will print all the key-value pairs in the dictionary
for key, value in my_dict.items():
print(f"{key}: {value}")
# This will print all the keys in the dictionary
for key in my_dict:
print(key)
# This will print all the values in the dictionary
for value in my_dict.values():
print(value)
Using the sorted function:
# This will create a new list with the keys of the dictionary sorted in ascending order sorted_keys = sorted(my_dict) # This will create a new list with the values of the dictionary sorted in ascending order sorted_values = sorted(my_dict.values())
Using the items function:
# This will create a new list with the key-value pairs in the dictionary as tuples items = list(my_dict.items())
Using defaultdict:
from collections import defaultdict
# This will create a defaultdict with a default value of 0 my_defaultdict = defaultdict(int) # This will increment the value for key 'a' by 1 my_defaultdict['a'] += 1 # This will print 1 print(my_defaultdict['a']) # This will print 0, because 'b' has not been set yet print(my_defaultdict['b'])
Using Counter:
from collections import Counter # This will create a Counter from a list of elements my_counter = Counter(['a', 'b', 'c', 'a', 'b']) # This will print the count for each element print(my_counter) # This will print the most common elements and their counts print(my_counter.most_common())
Merging dictionaries:
# This will create a new dictionary with the key-value pairs from both dictionaries
merged_dict = {**dict1, **dict2}
# This will create a new dictionary with the key-value pairs from both dictionaries,
# using the update method
merged_dict = {}
merged_dict.update(dict1)
merged_dict.update(dict2)
Using a dictionary to store data in a matrix form:
# This creates a dictionary with keys (i, j) and values 0, for all i and j in the range 1 to 3
matrix = {(i, j): 0 for i in range(1, 4) for j in range(1, 4)}
# This will set the value at position (2, 3) to 5
matrix[(2, 3)] = 5
# This will print the value at position (2, 3)
print(matrix[(2, 3)])
# This will print the entire matrix
print(matrix)