How to call Python function by name dynamically using a string?

Question

I have a Python function call like so:

import torchvision
model = torchvision.models.resnet18(pretrained=configs.use_trained_models)

Which works fine.

If I attempt to make it dynamic:

import torchvision
model_name = 'resnet18'
model = torchvision.models[model_name](pretrained=configs.use_trained_models)

then it fails with:

TypeError: 'module' object is not subscriptable

Which makes sense since model is a module which exports a bunch of things, including the resnet functions:

# __init__.py for the "models" module
...
from .resnet import * 
...

How can I call this function dynamically without knowing ahead of time its name (other than that I get a string with the function name)?

Answer 1

You can use the getattr function:

import torchvision
model_name = 'resnet18'
model = getattr(torchvision.models, model_name)(pretrained=configs.use_trained_models)

This essentially is along the lines the same as the dot notation just in function form accepting a string to retrieve the attribute/method.

• Edy Bourne: Perfect! Thanks a lot!

Answer 2

The new APIs since Aug 2022 are as follows:

# returns list of available model names
torchvision.models.list_models()
# returns specified model with pretrained common weights
torchvision.models.get_model("alexnet", weights="DEFAULT")
# returns specified model with pretrained=False
torchvision.models.get_model("alexnet", weights=None)
# returns specified model with specified pretrained weights
torchvision.models.get_model("alexnet", weights=ResNet50_Weights.IMAGENET1K_V2)

Reference: https://pytorch.org/blog/easily-list-and-initialize-models-with-new-apis-in-torchvision/