CODEWITHSUNDEEP
pythontensorflow
Eric OUUU
Eric OUUU

Reputation: 23

What do parentheses do when used after a variable in Python?

This question might be stupid but I don't know Python well enough to know what's going on. So I was trying to learn TensorFlow and noticed this weird invocation:

model = Sequential(
   # ...
)

predictions = model(x_train[:1]).numpy()

Can someone please explain what model(x_train[:1]) is doing here? From what I can tell, model is an object that's already constructed above? Is this using the object as a method/function? Or is something else going on here?

Upvotes: 2

Views: 80

Answers (1)

Grantus
Grantus

Reputation: 86

In this case the Tensorflow authors have provided an implementation for the __call__ "magic method" in the tf.keras.Sequential class hierarchy.

This allows you to invoke the instance of the object as-if it were a function. The call to model = Sequential(...) initialises the class itself via the __init__ constructor. The model() calls into the __call__ magic method.

Tensorflow and torch use this as convenience wrapper for a forward pass through the network (in most cases).

Upvotes: 4

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