Sort dictionary by key/value in Python
A Python dictionary is a built-in data type that represents a collection of key-value pairs, where each key is associated with a value. It is an unordered, mutable, and iterable data structure that can store any type of data as keys and values. The keys of a dictionary are unique, immutable objects, while the values can be of any type and can be repeated.Sort a dictionary by value | Ascending/Descending
To sort a dictionary by its values in Python, you can use the sorted function with a lambda function as the key argument.
# define a dictionary
color_dict = {'red': 10, 'blue': 5, 'green': 20, 'yello': 15}
# sort the dictionary by value in ascending order
sorted_dict_asc = dict(sorted(color_dict.items(), key=lambda x: x[1]))
# sort the dictionary by value in descending order
sorted_dict_desc = dict(sorted(color_dict.items(), key=lambda x: x[1], reverse=True))
# print the sorted dictionaries
print(sorted_dict_asc)
print(sorted_dict_desc)
# Output:
{'blue': 5, 'red': 10, 'yello': 15, 'green': 20}
{'green': 20, 'yello': 15, 'red': 10, 'blue': 5}
In the above example, two sorted dictionaries are created: sorted_dict_asc is sorted by value in ascending order, and sorted_dict_desc is sorted by value in descending order. The sorted function is used with a lambda function as the key argument to specify the sorting criterion. The lambda function takes each key-value pair as an input (x) and returns its value (x[1]). If the reverse parameter is True, the sorting is done in descending order, otherwise it's done in ascending order. Finally, the sorted key-value pairs are converted back into dictionaries using the dict function.
Sort a dictionary by key | Ascending/Descending
To sort a dictionary by its keys in ascending or descending order in Python, you can use the sorted function with the items method of the dictionary as the argument, and specify the reverse parameter as True or False. Here's an example:
# define a dictionary
color_dict = {'red': 10, 'blue': 5, 'green': 20, 'yello': 15}
# sort the dictionary by key in ascending order
sorted_dict_asc = dict(sorted(color_dict.items()))
# sort the dictionary by key in descending order
sorted_dict_desc = dict(sorted(color_dict.items(), reverse=True))
# print the sorted dictionaries
print(sorted_dict_asc)
print(sorted_dict_desc)
# Output:
{'blue': 5, 'green': 20, 'red': 10, 'yello': 15}
{'yello': 15, 'red': 10, 'green': 20, 'blue': 5}
In the above example, two sorted dictionaries are created: sorted_dict_asc is sorted by key in ascending order, and sorted_dict_desc is sorted by key in descending order. The sorted function is used with the items method of the dictionary as the argument to specify the sorting criterion. If the reverse parameter is True, the sorting is done in descending order, otherwise it's done in ascending order. Finally, the sorted key-value pairs are converted back into dictionaries using the dict function.
How dictionary Sorting Algorithm works
The sorting algorithm for dictionaries in Python works differently for sorting by keys versus sorting by values.
When sorting a dictionary by keys, Python simply iterates over the dictionary keys and sorts them in ascending or descending order based on the specified criteria. This can be achieved by using the sorted() function, which returns a list of the sorted keys. Once you have the sorted keys, you can use them to access the corresponding values in the dictionary in the order you desire. When sorting a dictionary by values, the process is a bit more involved. Since Python dictionaries are inherently unordered, the values need to be extracted from the dictionary and sorted independently. To do this, you can use the items() method of the dictionary to create a list of key-value pairs, which can then be sorted based on the value. The sorted() function can again be used to accomplish this. Once the key-value pairs have been sorted by value, they can be used to create a new dictionary with the desired order. In both cases, the sorted() function uses a comparison function that determines the order of the keys or values. By default, the comparison function uses the less-than operator (<) to determine the order, but this can be customized by passing a key argument to the sorted() function.
What is lambda function
A lambda function in Python is a small anonymous function that can take any number of arguments, but can only have one expression. It is created using the keyword lambda, followed by a comma-separated list of arguments, and then the expression to be evaluated. Lambda functions are often used as a shortcut for defining simple functions that are only used once, or as arguments to higher-order functions that expect a function as input.
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