Filter array of objects in Python

Question

I'm using Python to dig through a pretty big project and dig up information about it. I'm able to create an array of ProjectFiles, however I'm having a hard time figuring out how to filter it.

class ProjectFile:
    def __init__(self, filename: str,
                 number_of_lines: int,
                 language: str,
                 repo: str,
                 size: int):
        self.filename = filename
        self.number_of_lines = number_of_lines
        self.language = language
        self.repo = repo
        self.size = size

How would I filter an array of ProjectFile objects for a specific repo?

For instance, let's say I wanted to filter for objects whose repo property is SomeCocoapod.

I've looked for examples of filter, but everything I've found uses simple examples like lists of str or int.

Hielke Walinga · Accepted Answer · 2020-05-03 15:48:09Z

21

You can select attributes of a class using the dot notation.

Suppose arr is an array of ProjectFile objects. Now you filter for SomeCocoapod using.

filter(lambda p: p.repo == "SomeCocoapod", arr)

NB: This returns a filter object, which is a generator. To have a filtered list back you can wrap it in a list constructor.

As a very Pythonic alternative you can use list comprehensions:

filtered_arr = [p for p in arr if p.repo == "SomeCocoapod"]

answered May 3, 2020 at 15:48

Hielke Walinga

2,8592 gold badges21 silver badges33 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Adrian Over a year ago

Awesome! On filtering with lambda, I needed to wrap the filter in a list and it works perfectly :)

RoadRunner · Accepted Answer · 2020-05-03 16:01:15Z

Lets say you had this simple list of two ProjectFile objects:

projects = [
    ProjectFile(
        filename="test1.txt",
        number_of_lines=1,
        language="English",
        repo="repo1",
        size=1,
    ),
    ProjectFile(
        filename="test2.txt", 
        number_of_lines=2, 
        language="German", 
        repo="repo2", 
        size=2
    ),
]

You could then filter out repo1 using the repo attribute inside a list comprehension:

filtered = [project for project in projects if project.repo == "repo1"]

The above assumes you have overriden __str__ or __repr__ inside your ProjectFile class to give you a string representation of the filtered objects. Otherwise you will get something like [<__main__.ProjectFile object at 0x000001E879278160>] returned(which is fine if that's what you want to see). You can have a look at How to print instances of a class using print()? for more information.

Collectives™ on Stack Overflow

Filter array of objects in Python

2 Answers 2

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related