Getting functions from Python file as passable objects

Question

I have a Python file from which I would like to get all functions. I want to pass these functions to another file in order to collect data about these functions. For Example.py:

class Example:

    def method_to_extract(name: str) -> none:
        print(name)

I want to extract this method as an object through the file name and pass it as an argument to another function, like

func = magic_method(Example.py) # returns method_to_extract as a callable object
collect_data(func)

Is this possible? So far, I have only been able to extract the names of functions as strings. However, that does not help me, as I want to collect data about the functions like the number of arguments, type hints, and more, and therefore need to be able to access the entire function. I also tried getting the function using func = getattr(class, funcname), but I wasn't able to pass func as a parameter and extract the data I need.

You'll need to actually import Example.py before being able to use getattr() or similar methods. If you need to you can do imports dynamically with importlib — Green Cloak Guy
– Green Cloak Guy, Commented Jan 2, 2021 at 14:04
it would be easier if you want to extract the functions from the class instead of the file — Aven Desta
– Aven Desta, Commented Jan 2, 2021 at 14:11
How does this work if I want the file name to be a variable? — Jakob0403
– Jakob0403, Commented Jan 2, 2021 at 14:14
How would it work for extracting functions from a class instead of a file? — Jakob0403
– Jakob0403, Commented Jan 2, 2021 at 14:15

Szymon Kowaliński · Accepted Answer · 2021-01-02 14:21:40Z

1

I can think of 3 solutions, dependant on your particular needs.

Simplest one: don't use classes, just global functions:

# file1.py
def method_to_extract(name):
    print(name)

And then in another file just import and use it:

# file2.py
from file2 import method_to_extract
method_to_extract()

In case you especially want to use methods inside of a class, you can make them static with @staticmethod decorator:
```
# file1.py
class Example:
    @staticmethod
    def method_to_extract(name):
        print(name)
```
And then in another file just import and use it:
```
# file2.py
from file2 import Example
Example.method_to_extract()
```
More on staticmetod decorator here: https://www.programiz.com/python-programming/methods/built-in/staticmethod
Of course, not all of your methods can be static. Then you just have to create an instance of the class and then use its methods:
```
# file1.py
class Example:
    def method_to_extract(name):
        print(name)
```
And then in another file just import and use it:
```
# file2.py
from file2 import Example
instance = Example()
instance.method_to_extract()
```

Basically, the above three approaches are in general only possible ways of accessing some particular function or method in python and the fact of exporting them to another file doesn't change a thing.

answered Jan 2, 2021 at 14:21

Szymon Kowaliński

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2 Comments

Jakob0403 Over a year ago

Thank you! But if I don't want the code to be static, rather handle any type of file given to it and extract data for the functions contained in that file, I can't use any of these solutions, or am I missing something here? Basically I want to be able to extract all methods from any python file and collect data about these methods. If you consider that I may not even know what is in the files I want to evaluate, this solution does not really work, unless I'm missing something here.

Szymon Kowaliński Over a year ago

I would say it's a very weird use case. Maybe you will find something helpful here : stackoverflow.com/questions/1911281/…

tripleee · Accepted Answer · 2021-01-02 14:12:05Z

1

Something like this:

from Example import Example.method_to_extract as mte
collect_data(mte)

The code you show is not entirely correct; you would have to make method_to_extract a @staticmethod if it's inside the Example class. Perhaps a better solution then would be to define it outside the class; or define a @classmethod which you can call to return a method of that class as an object. But both of these are generally best avoided; your class should probably simply have a method which implements collect_data, and your code should simply call that instead.

answered Jan 2, 2021 at 14:12

tripleee

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4 Comments

Jakob0403 Over a year ago

Thanks! I agree, the solution is not perfect. However, I can't add a method collect_data to the class, as the code I want to extract the data from is not mine. Ideally, I want to have a class which gets a python file name as an argument, then collects data from the functions in that file, with the file name being variable.

tripleee Over a year ago

You know about inheritance, right? You don't need to change the original code, just extend it.

Jakob0403 Over a year ago

I considered that, but since I want my code to be flexible and work for any type of python file, I can't extend every single file I want to evaluate.

Ekrem Dinçel Over a year ago

@Jakob0403 any type of python file I think you have an misunderstanding of Python's module system.

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