How to beginner · 3 min read

How to log hyperparameters with wandb

Quick answer

Use wandb.init() with the config parameter to log hyperparameters at the start of your run. You can also update hyperparameters anytime with wandb.config.update(). This enables easy experiment tracking and visualization.

PREREQUISITES

Python 3.8+
pip install wandb
wandb account (free)
wandb login via CLI

Setup

Install wandb via pip and authenticate your account to enable logging.

bash

pip install wandb
wandb login

Step by step

Initialize a wandb run with hyperparameters passed as a dictionary to config. Log metrics during training and finish the run.

python

import wandb

# Define hyperparameters
hyperparams = {
    "learning_rate": 0.001,
    "batch_size": 32,
    "epochs": 10
}

# Initialize a new wandb run with config
wandb.init(project="my-project", config=hyperparams)

# Access hyperparameters via wandb.config
config = wandb.config
print(f"Learning rate: {config.learning_rate}")

# Simulate training loop
for epoch in range(config.epochs):
    # Dummy metric
    accuracy = 0.8 + epoch * 0.01
    # Log metrics
    wandb.log({"epoch": epoch, "accuracy": accuracy})

wandb.finish()

output

Learning rate: 0.001

Common variations

Update hyperparameters mid-run with wandb.config.update().
Log hyperparameters separately using wandb.config attributes.
Use wandb.init() without config and set hyperparameters later.

python

import wandb

wandb.init(project="my-project")

# Update hyperparameters after init
wandb.config.update({"learning_rate": 0.002, "batch_size": 64})

print(f"Updated batch size: {wandb.config.batch_size}")

wandb.finish()

output

Updated batch size: 64

Troubleshooting

If metrics or hyperparameters don't appear in the dashboard, ensure you called wandb.finish() to flush logs.
Check your internet connection and wandb login status.
Use wandb CLI commands like wandb status to verify run status.

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Key Takeaways

Pass hyperparameters as a dictionary to wandb.init(config=...) for automatic logging.
Use wandb.config.update() to modify hyperparameters during a run.
Always call wandb.finish() to ensure logs are uploaded and visible in the dashboard.

Verified 2026-04

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