Fine-Tuning With the Trainer API
Train a classifier on your data.
Fine-Tuning With the Trainer API is a free NLP Academy lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the NLP Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why Fine-Tune
A pretrained model already knows language; fine-tuning nudges it to excel at your specific task using your labeled data.
Start From a Checkpoint
Load a model with a classification head sized to your labels. The base weights are reused, only the head starts fresh.
from transformers import AutoModelForSequenceClassification
m = AutoModelForSequenceClassification.from_pretrained("bert-base-uncased", num_labels=2)Meet the Trainer
The Trainer API handles the whole training loop for you: batching, gradients, evaluation, and saving, all in one class.
Prepare Your Dataset
Tokenize your text and keep the labels. A Hugging Face Dataset object plugs straight into the Trainer.
ds = ds.map(lambda x: tok(x["text"], truncation=True), batched=True)Set Training Arguments
TrainingArguments collects every knob in one place: learning rate, batch size, epochs, and where to save checkpoints.
from transformers import TrainingArguments
args = TrainingArguments("out", num_train_epochs=3)Build the Trainer
Pass the model, args, and your datasets into the Trainer. Now everything it needs to learn lives in one object.
from transformers import Trainer
trainer = Trainer(model=m, args=args, train_dataset=train, eval_dataset=val)Launch Training
A single call runs the full loop. The Trainer steps through epochs and updates the weights as it learns.
trainer.train()Learning Rate Matters
Fine-tuning uses a small learning rate, often around 2e-5, so you adjust the pretrained weights gently instead of wrecking them.
Just a Few Epochs
Transformers usually need only two to four passes over the data. Too many epochs and the model starts to overfit.
Track Metrics
Give the Trainer a compute_metrics function and it reports accuracy or F1 each evaluation, so you watch progress live.
trainer = Trainer(..., compute_metrics=metric_fn)Use a Data Collator
A data collator pads each batch dynamically to its longest example, saving memory versus padding everything to one length.
Quick Check
Why does fine-tuning use a small learning rate?
Recap
Load a model with a fresh head, tokenize your data, set TrainingArguments, then let the Trainer run a few low-rate epochs. ✅
Frequently asked questions
Is the “Fine-Tuning With the Trainer API” lesson free?
Yes — the full text of “Fine-Tuning With the Trainer API” is free to read here on the web, and the NLP Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the NLP Academy course, upgrade to CoddyKit PRO.
What will I learn in “Fine-Tuning With the Trainer API”?
Train a classifier on your data. You practise NLP Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start NLP Academy?
No prior experience is required. NLP Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Fine-Tuning With the Trainer API” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this NLP Academy lesson?
Yes. Every NLP Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- The Transformers Library Tour
- Tokenizing for Transformer Models
- Fine-Tuning With the Trainer API
- Evaluating and Saving Your Model