CODEWITHSUNDEEP
pythonpython-3.xoop
Adrian
Adrian

Reputation: 16725

Filter array of objects in Python

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.

Upvotes: 18

Views: 26234

Answers (2)

RoadRunner
RoadRunner

Reputation: 26315

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.

Upvotes: 3

Hielke Walinga
Hielke Walinga

Reputation: 2845

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"]

Upvotes: 21

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