Sorting a list of dictionaries by a value
In Python, you can sort a list of dictionaries by a value using the ‘sorted‘ function and providing a ‘key‘ function that returns the value to sort by. For example, consider the following list of dictionaries:
list_of_dicts = [{"name": "John", "age": 28},
{"name": "Jane", "age": 31},
{"name": "Jim", "age": 25}]
To sort this list of dictionaries by the "age" key, you can do the following:
sorted_list_of_dicts = sorted(list_of_dicts, key=lambda x: x["age"])
This will return a new list of dictionaries sorted by the value of the "age" key in ascending order. To sort in descending order, you can use the ‘reverse‘ argument:
sorted_list_of_dicts = sorted(list_of_dicts, key=lambda x: x["age"], reverse=True)
The above code will return a new list of dictionaries sorted by the value of the "age" key in descending order.
Add Keys and Sort in a Loop in Dictionary
To add values to a dictionary and sort the dictionary by values in a loop, you can use the built-in ‘sorted()‘ function along with a lambda function to specify the sorting key. Here’s an example:
# Initialize an empty dictionary
my_dict = {}
# Loop to add values to the dictionary
while True:
# Get user input for key and value
key = input("Enter a key (or 'quit' to exit): ")
if key == 'quit':
break
value = int(input("Enter a value: "))
# Add the key-value pair to the dictionary
my_dict[key] = value
# Sort the dictionary by values and print the result
sorted_dict = dict(sorted(my_dict.items(), key=lambda item: item[1]))
print(sorted_dict)
In this example, we start with an empty dictionary ‘my_dict‘. We then use a ‘while‘ loop to repeatedly ask the user for a key-value pair to add to the dictionary. If the user enters 'quit', the loop breaks and the program ends. Otherwise, the program adds the key-value pair to the dictionary using the square bracket notation.
After each key-value pair is added to the dictionary, the program uses the ‘sorted()‘ function to sort the dictionary by values, using a lambda function to specify the sorting key. The lambda function takes an item (i.e., a key-value pair) and returns the value of the item, which is used for sorting. The result of ‘sorted()‘ is a list of tuples, where each tuple contains a key-value pair from the dictionary, sorted by value.
We then use the ‘dict()‘ function to convert the sorted list of tuples back to a dictionary, and assign it to ‘sorted_dict‘. Finally, we print ‘sorted_dict‘ using the ‘print()‘ function.
Note that this code will sort the dictionary after each key-value pair is added, so the order of the dictionary may change with each iteration of the loop. If you want to sort the dictionary only once, after all key-value pairs have been added, you can move the sorting code outside the loop.
Sort a Dictionary in Reverse order
To sort a dictionary in reverse order, you can use the ‘sorted()‘ function with the ‘reverse=True‘ parameter. Here’s an example:
# Create a dictionary
my_dict = {'Alice': 25, 'Bob': 30, 'Charlie': 35, 'Dave': 40}
# Sort the dictionary in reverse order
sorted_dict = dict(sorted(my_dict.items(), key=lambda item: item[1], reverse=True))
# Print the sorted dictionary
print(sorted_dict)
In this example, we start with a dictionary ‘my_dict‘ that contains four key-value pairs. We then use the ‘sorted()‘ function to sort the dictionary by values in reverse order, using a lambda function to specify the sorting key. The ‘reverse=True‘ parameter tells the ‘sorted()‘ function to sort in reverse order.
We then use the ‘dict()‘ function to convert the sorted list of tuples back to a dictionary, and assign it to ‘sorted_dict‘. Finally, we print ‘sorted_dict‘ using the ‘print()‘ function. The output of this code will be:
{'Dave': 40, 'Charlie': 35, 'Bob': 30, 'Alice': 25}
As you can see, the dictionary is sorted in reverse order by values, with the key-value pair 'Dave': 40' appearing first and the key-value pair 'Alice': 25' appearing last.