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Keras Tables

Try in a Colab Notebook here โ†’

Use Weights & Biases for machine learning experiment tracking, dataset versioning, and project collaboration.

Weights & Biases

This colab notebook introduces the WandbEvalCallback which is an abstract callback that be inherited to build useful callbacks for model prediction visualization and dataset visualization. Refer to the ๐Ÿ’ซ WandbEvalCallback section for more details.

๐ŸŒด Setup and Installation

First, let us install the latest version of Weights and Biases. We will then authenticate this colab instance to use W&B.

!pip install -qq -U wandb
import os
import numpy as np
import tensorflow as tf
from tensorflow.keras import layers
from tensorflow.keras import models
import tensorflow_datasets as tfds

# Weights and Biases related imports
import wandb
from wandb.keras import WandbMetricsLogger
from wandb.keras import WandbModelCheckpoint
from wandb.keras import WandbEvalCallback

If this is your first time using W&B or you are not logged in, the link that appears after running wandb.login() will take you to sign-up/login page. Signing up for a free account is as easy as a few clicks.


๐ŸŒณ Hyperparameters

Use of proper config system is a recommended best practice for reproducible machine learning. We can track the hyperparameters for every experiment using W&B. In this colab we will be using simple Python dict as our config system.

configs = dict(
num_classes = 10,
shuffle_buffer = 1024,
batch_size = 64,
image_size = 28,
image_channels = 1,
earlystopping_patience = 3,
learning_rate = 1e-3,
epochs = 10

๐Ÿ Dataset

In this colab, we will be using CIFAR100 dataset from TensorFlow Dataset catalog. We aim to build a simple image classification pipeline using TensorFlow/Keras.

train_ds, valid_ds = tfds.load('fashion_mnist', split=['train', 'test'])

def parse_data(example):
# Get image
image = example["image"]
# image = tf.image.convert_image_dtype(image, dtype=tf.float32)

# Get label
label = example["label"]
label = tf.one_hot(label, depth=configs["num_classes"])

return image, label

def get_dataloader(ds, configs, dataloader_type="train"):
dataloader =, num_parallel_calls=AUTOTUNE)

if dataloader_type=="train":
dataloader = dataloader.shuffle(configs["shuffle_buffer"])

dataloader = (

return dataloader
trainloader = get_dataloader(train_ds, configs)
validloader = get_dataloader(valid_ds, configs, dataloader_type="valid")

๐ŸŽ„ Model

def get_model(configs):
backbone = tf.keras.applications.mobilenet_v2.MobileNetV2(weights='imagenet', include_top=False)
backbone.trainable = False

inputs = layers.Input(shape=(configs["image_size"], configs["image_size"], configs["image_channels"]))
resize = layers.Resizing(32, 32)(inputs)
neck = layers.Conv2D(3, (3,3), padding="same")(resize)
preprocess_input = tf.keras.applications.mobilenet.preprocess_input(neck)
x = backbone(preprocess_input)
x = layers.GlobalAveragePooling2D()(x)
outputs = layers.Dense(configs["num_classes"], activation="softmax")(x)

return models.Model(inputs=inputs, outputs=outputs)
model = get_model(configs)

๐ŸŒฟ Compile Model

optimizer = "adam",
loss = "categorical_crossentropy",
metrics = ["accuracy", tf.keras.metrics.TopKCategoricalAccuracy(k=5, name='top@5_accuracy')]

๐Ÿ’ซ WandbEvalCallback

The WandbEvalCallback is an abstract base class to build Keras callbacks for primarily model prediction visualization and secondarily dataset visualization.

This is a dataset and task agnostic abstract callback. To use this, inherit from this base callback class and implement the add_ground_truth and add_model_prediction methods.

The WandbEvalCallback is a utility class that provides helpful methods to:

  • create data and prediction wandb.Table instances,
  • log data and prediction Tables as wandb.Artifact,
  • logs the data table on_train_begin,
  • logs the prediction table on_epoch_end.

As an example, we have implemented WandbClfEvalCallback below for an image classification task. This example callback:

  • logs the validation data (data_table) to W&B,
  • performs inference and logs the prediction (pred_table) to W&B on every epoch end.

How the memory footprint is reduced?โ€‹

We log the data_table to W&B when the on_train_begin method is ivoked. Once it's uploaded as a W&B Artifact, we get a reference to this table which can be accessed using data_table_ref class variable. The data_table_ref is a 2D list that can be indexed like self.data_table_ref[idx][n] where idx is the row number while n is the column number. Let's see the usage in the example below.

class WandbClfEvalCallback(WandbEvalCallback):
def __init__(
self, validloader, data_table_columns, pred_table_columns, num_samples=100
super().__init__(data_table_columns, pred_table_columns)

self.val_data = validloader.unbatch().take(num_samples)

def add_ground_truth(self, logs=None):
for idx, (image, label) in enumerate(self.val_data):
np.argmax(label, axis=-1)

def add_model_predictions(self, epoch, logs=None):
# Get predictions
preds = self._inference()
table_idxs = self.data_table_ref.get_index()

for idx in table_idxs:
pred = preds[idx]

def _inference(self):
preds = []
for image, label in self.val_data:
pred = self.model(tf.expand_dims(image, axis=0))
argmax_pred = tf.argmax(pred, axis=-1).numpy()[0]

return preds

๐ŸŒป Train

# Initialize a W&B run
run = wandb.init(
project = "intro-keras",
config = configs

# Train your model
epochs = configs["epochs"],
validation_data = validloader,
callbacks = [
data_table_columns=["idx", "image", "ground_truth"],
pred_table_columns=["epoch", "idx", "image", "ground_truth", "prediction"]
) # Notice the use of WandbEvalCallback here

# Close the W&B run
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