Description

get top n values in dictionary python ?

### Python: Retrieving the Top N Values from a Dictionary

In numerous programming tasks, especially with data analysis and web development, you often need to extract the top N key-value pairs from a dictionary based on their values. Python offers several methods to achieve this, and in this post, I’ll walk you through some efficient techniques. Let’s dive in!

#### The Original Dictionary
Suppose we have a dictionary with the following format:
“`python
my_dict = {‘best’: 6, ‘gfg’: 1, ‘geeks’: 3, ‘for’: 7, ‘is’: 4}
“`
We aim to extract the top N key-value pairs with the highest values from this dictionary. Let’s explore different methods.

#### Method 1: Using `nlargest()` from `heapq` Library
The simplest way to get the top N key-value pairs is by using the `nlargest()` function from the built-in `heapq` library. Here’s how you can do it:

“`python
import heapq

my_dict = {‘best’: 6, ‘gfg’: 1, ‘geeks’: 3, ‘for’: 7, ‘is’: 4}
n = 3
top_n_pairs = heapq.nlargest(n, my_dict.items(), key=lambda item: item[1])

# Convert list of tuples back to dictionary
top_n_dict = dict(top_n_pairs)
print(top_n_dict)
“`
This script outputs:
“`python
{‘for’: 7, ‘is’: 4, ‘best’: 6}
“`

#### Method 2: Using `sorted()`
Another approach is to sort the dictionary based on its values and then slice the top N pairs. Here’s how we can do it:

“`python
my_dict = {‘best’: 6, ‘gfg’: 1, ‘geeks’: 3, ‘for’: 7, ‘is’: 4}
n = 3
sorted_dict = dict(sorted(my_dict.items(), key=lambda item: item[1], reverse=True)[:n])

print(sorted_dict)
“`
This will also output:
“`python
{‘for’: 7, ‘is’: 4, ‘best’: 6}
“`
While this method is intuitive and works perfectly fine, the `nlargest()` function from the `heapq` module is generally faster for larger dictionaries as it does not require sorting the entire dictionary.

#### Tips for Performance and Best Practices
– **Using Built-in Functions:** Prefer Python’s built-in functions and modules like `heapq` for efficient and clean code.
– **Dictionary Order in Python 3.7+** Python 3.7+ maintains insertion order in dictionaries, so you can directly sort or use `nlargest()` which will return the correct order.
– **Mutable State:** Be cautious when changing the original dictionary if you do not wish to alter it. Use copies (`my_dict.copy()`) or create new dictionaries when using functions that modify the state.

### Conclusion
Extracting the top N values from a dictionary is a common task, and Python provides several ways to accomplish this efficiently. Among the discussed methods, `nlargest()` from the `heapq` library is one of the most efficient ways to fetch the desired result.

Feel free to reach out if you have any questions or need further clarification on any of these methods. Happy coding!

—

### Resources:
– [GeeksforGeeks: Python | N largest values in dictionary](https://www.geeksforgeeks.org/python-n-largest-values-in-dictionary/)
– [StackOverflow: Python get top n keys with value as dictionary](https://stackoverflow.com/questions/38218501/python-get-top-n-keys-with-value-as-dictionary)
– [StackOverflow: Top values from dictionary](https://stackoverflow.com/questions/11902665/top-values-from-dictionary)
– [StackExchange: Python 3 Get n greatest elements in dictionary](https://codereview.stackexchange.com/questions/165056/python-3-get-n-greatest-elements-in-dictionary)
– [DataScienceParichay: Get Dictionary Values](https://datascienceparichay.com/article/python-get-dictionary-values/)
– [W3Schools: Python Dictionary values() Method](https://www.w3schools.com/python/ref_dictionary_values.asp)
– [Python Guides: Get all values from a dictionary Python](https://pythonguides.com/get-all-values-from-a-dictionary-python/)
– [Youtube Tutorial](https://www.youtube.com/watch?v=R-1-lyjyiPg) by Lesoutrali Bot

Stay tuned for more such Python-related articles. Keep learning!