How to Filter a Dictionary Using a Condition Function in Python?

Filtering a Dictionary Using a Condition Function

Python dictionaries, ubiquitous in data manipulation tasks, provide a powerful way to store and retrieve information based on keys. However, there may come situations where you need to extract a subset of the dictionary's contents based on specific criteria. Let's explore an example where we want to filter a dictionary to select points whose x and y coordinates are both less than 5.

Original Approach

One possible approach involves iterating over the dictionary items, checking the coordinates of each point, and selecting those that meet the condition. This approach, while straightforward, can be verbose and error-prone.

points = {'a': (3, 4), 'b': (1, 2), 'c': (5, 5), 'd': (3, 3)}
points_small = {}
for item in [i for i in points.items() if i[1][0] < 5 and i[1][1] < 5]:
    points_small[item[0]] = item[1]

Elegant Solution

Python provides a more elegant solution using dict comprehensions. Dict comprehensions allow you to create a new dictionary based on a specified condition, with the syntax: {k: v for k, v in existing_dict if condition}. In our case, we can use this syntax to create the filtered dictionary:

{k: v for k, v in points.items() if v[0] < 5 and v[1] < 5}

Python 2 Compatibility

In Python 2, the iteritems() method is used instead of items(). The code for Python 2 would be:

{k: v for k, v in points.iteritems() if v[0] < 5 and v[1] < 5}

This compact and expressive syntax makes it easy to manipulate dictionaries and extract specific data based on conditions. Python's dict comprehensions offer a powerful tool for filtering and transforming dictionary contents efficiently and concisely.

The above is the detailed content of How to Filter a Dictionary Using a Condition Function in Python?. For more information, please follow other related articles on the PHP Chinese website!