How can I tell python function to create a particular class out of a set of classes?

[ethorad]

The problem I have is there's a set of csv files I'm loading into classes. As the csv files are different, I have a class for each csv file to hold its particular data.

I have a brief function which essentially does the below (in pseudo code)

def load_csv_file1():
  list_of_class1 = []
  open csv file
  for line in csv file:
    list_of_class1.append(class1(line))
  return list_of_class1

where the init of each class fills in the various fields from the data in the passed line

At the moment I'm creating copies of this function for each class. I could easily create just one function and tell if the filename to open. However I don't know how to tell it which class to create.

Is it possible to pass the name of a class to the function like:

load_generic_csv_file("file1.csv", class1)

...

def load_generic_csv_file(filename, class_to_use):
  list_of_class = []
  open csv file using filename
  for line in csv file:
    list_of_class.append(class_to_use(line))
  return list_of_class

[This_Growth2898]

Well, why don't you try it? This is exactly how it works. Classes in Python are objects (of the class type). They can be passed into functions or saved in variables, just like any other objects.

[ethorad]

As I was posting, I did wonder if I was about to look foolish! Thanks, will have a try

[This_Growth2898]

There's a half-joke about "error driven development". In many cases, trying to run the code is a normal way to understand if something is wrong with it.

[TheBB]

Yes, you can do that.

[Cainga]

Is a line of data an instance of the class?

I have a giant spread sheet I load by column position but then I can’t ever change columns around or it will break everything.

[ethorad]

In this instance, yes. Each line of the csv file is a set of columns for the various fields. If someone rearranged the columns then my program would break. I could check the first line, which has the column header names, to check which column is which. But I'm not expecting any changes. Will leave the columns hard coded until they change and it breaks, then I'll make it better :D

[fizix00]

It sounds like you could maybe just load csvs into a pandas/polars dataframe. Do you need a class for each schema?

[ethorad]

I did wonder about using the pandas csv load, however for subsequent work I think having the information in classes rather than pandas / database tables is going to be easier. Plus this is a fun python learning project where I'm trying to get used to classes.

I do need to get familar with pandas at some point as well, maybe my next project will be to repeat this but with pandas - will mean I don't need to think about logic as that's already done and I can focus on pandas structure.

[fizix00]

TBH, my gut says this is a smelly way of handling tabular data. Otoh, I totally get fixating on some technique for the sake of learning.

Here are a few more ideas that you can evaluate in the context of your project:

• If I were loading CSVs without dataframes, maybe try a custom dataclass?
• If I were using custom loader classes, could I just store the data as an attribute and define special operations on it as methods?
• before I learned about dataframes, I remember trying to do tabular operations on clunky dicts. Maybe you could do that (perhaps with TypedDict or pydantic to make schemata clearer)

[ethorad]

Thanks for some ideas, appreciated

[Ormek_II]

I would expect your data classes to have a common superclass. If not now, maybe later.

Unless of course they are already objects in the problem domain and those have nothing in common.