How do you filter an 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.

RoadRunner

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asked May 3, 2020 at 15:40

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 WalingaHielke Walinga

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1

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.

answered May 3, 2020 at 15:48

RoadRunnerRoadRunner

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Python filter Array of objects And print the label for each object, you could use a loop or a list comprehension.

We filter an array of ProjectFile objects for a specific repo. Select attributes of a class using the dot notation.

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

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


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
    ),
]

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

print([projects.repo + " " + projects.language for projects in res])

Output:

As a very Pythonic alternative you can use list comprehensions:

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

Source: stackoverflow.com

Do comment if you have any doubts or suggestions on this Python code.

Note: IDE: PyCharm 2021.3.3 (Community Edition)

Windows 10

Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.

Degree in Computer Science and Engineer: App Developer and has multiple Programming languages experience. Enthusiasm for technology & like learning technical.

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