
Quick tour
[[open-in-colab]]
Get up and running with 🤗 Transformers! Whether you're a developer or an everyday user, this quick tour will help you get started and show you how to use the [pipeline] for inference, load a pretrained model and preprocessor with an AutoClass, and quickly train a model with PyTorch or TensorFlow. If you're a beginner, we recommend checking out our tutorials or course next for more in-depth explanations of the concepts introduced here.
Before you begin, make sure you have all the necessary libraries installed:

!pip install transformers datasets
You'll also need to install your preferred machine learning framework:

pip install torch

pip install tensorflow

Pipeline

The [pipeline] is the easiest and fastest way to use a pretrained model for inference. You can use the [pipeline] out-of-the-box for many tasks across different modalities, some of which are shown in the table below:

For a complete list of available tasks, check out the pipeline API reference.

| Task                     | Description                                                                                              | Modality    | Pipeline identifier                       |
|------------------------------|--------------------------------------------------------------------------------------------------------------|-----------------|-----------------------------------------------|
| Text classification          | assign a label to a given sequence of text                                                                   | NLP             | pipeline(task=“sentiment-analysis”)           |
| Text generation              | generate text given a prompt                                                                                 | NLP             | pipeline(task=“text-generation”)              |
| Summarization                | generate a summary of a sequence of text or document                                                         | NLP             | pipeline(task=“summarization”)                |
| Image classification         | assign a label to an image                                                                                   | Computer vision | pipeline(task=“image-classification”)         |
| Image segmentation           | assign a label to each individual pixel of an image (supports semantic, panoptic, and instance segmentation) | Computer vision | pipeline(task=“image-segmentation”)           |
| Object detection             | predict the bounding boxes and classes of objects in an image                                                | Computer vision | pipeline(task=“object-detection”)             |
| Audio classification         | assign a label to some audio data                                                                            | Audio           | pipeline(task=“audio-classification”)         |
| Automatic speech recognition | transcribe speech into text                                                                                  | Audio           | pipeline(task=“automatic-speech-recognition”) |
| Visual question answering    | answer a question about the image, given an image and a question                                             | Multimodal      | pipeline(task=“vqa”)                          |
| Document question answering  | answer a question about the document, given a document and a question                                        | Multimodal      | pipeline(task="document-question-answering")  |
| Image captioning             | generate a caption for a given image                                                                         | Multimodal      | pipeline(task="image-to-text")                |
Start by creating an instance of [pipeline] and specifying a task you want to use it for. In this guide, you'll use the [pipeline] for sentiment analysis as an example:

from transformers import pipeline
classifier = pipeline("sentiment-analysis")

The [pipeline] downloads and caches a default pretrained model and tokenizer for sentiment analysis. Now you can use the classifier on your target text:

classifier("We are very happy to show you the 🤗 Transformers library.")
[{'label': 'POSITIVE', 'score': 0.9998}]

If you have more than one input, pass your inputs as a list to the [pipeline] to return a list of dictionaries:

results = classifier(["We are very happy to show you the 🤗 Transformers library.", "We hope you don't hate it."])
for result in results:
     print(f"label: {result['label']}, with score: {round(result['score'], 4)}")
label: POSITIVE, with score: 0.9998
label: NEGATIVE, with score: 0.5309

The [pipeline] can also iterate over an entire dataset for any task you like. For this example, let's choose automatic speech recognition as our task:

import torch
from transformers import pipeline
speech_recognizer = pipeline("automatic-speech-recognition", model="facebook/wav2vec2-base-960h")

Load an audio dataset (see the 🤗 Datasets Quick Start for more details) you'd like to iterate over. For example, load the MInDS-14 dataset:

from datasets import load_dataset, Audio
dataset = load_dataset("PolyAI/minds14", name="en-US", split="train")  # doctest: +IGNORE_RESULT

You need to make sure the sampling rate of the dataset matches the sampling 
rate facebook/wav2vec2-base-960h was trained on:

dataset = dataset.cast_column("audio", Audio(sampling_rate=speech_recognizer.feature_extractor.sampling_rate))

The audio files are automatically loaded and resampled when calling the "audio" column.
Extract the raw waveform arrays from the first 4 samples and pass it as a list to the pipeline:

result = speech_recognizer(dataset[:4]["audio"])
print([d["text"] for d in result])
['I WOULD LIKE TO SET UP A JOINT ACCOUNT WITH MY PARTNER HOW DO I PROCEED WITH DOING THAT', "FONDERING HOW I'D SET UP A JOIN TO HELL T WITH MY WIFE AND WHERE THE AP MIGHT BE", "I I'D LIKE TOY SET UP A JOINT ACCOUNT WITH MY PARTNER I'M NOT SEEING THE OPTION TO DO IT ON THE APSO I CALLED IN TO GET SOME HELP CAN I JUST DO IT OVER THE PHONE WITH YOU AND GIVE YOU THE INFORMATION OR SHOULD I DO IT IN THE AP AN I'M MISSING SOMETHING UQUETTE HAD PREFERRED TO JUST DO IT OVER THE PHONE OF POSSIBLE THINGS", 'HOW DO I FURN A JOINA COUT']

For larger datasets where the inputs are big (like in speech or vision), you'll want to pass a generator instead of a list to load all the inputs in memory. Take a look at the pipeline API reference for more information.
Use another model and tokenizer in the pipeline
The [pipeline] can accommodate any model from the Hub, making it easy to adapt the [pipeline] for other use-cases. For example, if you'd like a model capable of handling French text, use the tags on the Hub to filter for an appropriate model. The top filtered result returns a multilingual BERT model finetuned for sentiment analysis you can use for French text:

model_name = "nlptown/bert-base-multilingual-uncased-sentiment"

Use [AutoModelForSequenceClassification] and [AutoTokenizer] to load the pretrained model and it's associated tokenizer (more on an AutoClass in the next section):

from transformers import AutoTokenizer, AutoModelForSequenceClassification
model = AutoModelForSequenceClassification.from_pretrained(model_name)
tokenizer = AutoTokenizer.from_pretrained(model_name)
``
</pt>
<tf>
Use [TFAutoModelForSequenceClassification] and [AutoTokenizer] to load the pretrained model and it's associated tokenizer (more on anTFAutoClass` in the next section):

from transformers import AutoTokenizer, TFAutoModelForSequenceClassification
model = TFAutoModelForSequenceClassification.from_pretrained(model_name)
tokenizer = AutoTokenizer.from_pretrained(model_name)

Specify the model and tokenizer in the [pipeline], and now you can apply the classifier on French text:

classifier = pipeline("sentiment-analysis", model=model, tokenizer=tokenizer)
classifier("Nous sommes très heureux de vous présenter la bibliothèque 🤗 Transformers.")
[{'label': '5 stars', 'score': 0.7273}]

If you can't find a model for your use-case, you'll need to finetune a pretrained model on your data. Take a look at our finetuning tutorial to learn how. Finally, after you've finetuned your pretrained model, please consider sharing the model with the community on the Hub to democratize machine learning for everyone! 🤗
AutoClass

Under the hood, the [AutoModelForSequenceClassification] and [AutoTokenizer] classes work together to power the [pipeline] you used above. An AutoClass is a shortcut that automatically retrieves the architecture of a pretrained model from its name or path. You only need to select the appropriate AutoClass for your task and it's associated preprocessing class. 
Let's return to the example from the previous section and see how you can use the AutoClass to replicate the results of the [pipeline].
AutoTokenizer
A tokenizer is responsible for preprocessing text into an array of numbers as inputs to a model. There are multiple rules that govern the tokenization process, including how to split a word and at what level words should be split (learn more about tokenization in the tokenizer summary). The most important thing to remember is you need to instantiate a tokenizer with the same model name to ensure you're using the same tokenization rules a model was pretrained with.
Load a tokenizer with [AutoTokenizer]:

from transformers import AutoTokenizer
model_name = "nlptown/bert-base-multilingual-uncased-sentiment"
tokenizer = AutoTokenizer.from_pretrained(model_name)

Pass your text to the tokenizer:

encoding = tokenizer("We are very happy to show you the 🤗 Transformers library.")
print(encoding)
{'input_ids': [101, 11312, 10320, 12495, 19308, 10114, 11391, 10855, 10103, 100, 58263, 13299, 119, 102],
 'token_type_ids': [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
 'attention_mask': [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]}

The tokenizer returns a dictionary containing:

input_ids: numerical representations of your tokens.
attention_mask: indicates which tokens should be attended to.

A tokenizer can also accept a list of inputs, and pad and truncate the text to return a batch with uniform length:

pt_batch = tokenizer(
     ["We are very happy to show you the 🤗 Transformers library.", "We hope you don't hate it."],
     padding=True,
     truncation=True,
     max_length=512,
     return_tensors="pt",
 )
</pt>
<tf>py
tf_batch = tokenizer(
     ["We are very happy to show you the 🤗 Transformers library.", "We hope you don't hate it."],
     padding=True,
     truncation=True,
     max_length=512,
     return_tensors="tf",
 )

Check out the preprocess tutorial for more details about tokenization, and how to use an [AutoImageProcessor], [AutoFeatureExtractor] and [AutoProcessor] to preprocess image, audio, and multimodal inputs.

AutoModel

🤗 Transformers provides a simple and unified way to load pretrained instances. This means you can load an [AutoModel] like you would load an [AutoTokenizer]. The only difference is selecting the correct [AutoModel] for the task. For text (or sequence) classification, you should load [AutoModelForSequenceClassification]:

from transformers import AutoModelForSequenceClassification
model_name = "nlptown/bert-base-multilingual-uncased-sentiment"
pt_model = AutoModelForSequenceClassification.from_pretrained(model_name)

See the task summary for tasks supported by an [AutoModel] class.

Now pass your preprocessed batch of inputs directly to the model. You just have to unpack the dictionary by adding **:

pt_outputs = pt_model(**pt_batch)

The model outputs the final activations in the logits attribute. Apply the softmax function to the logits to retrieve the probabilities:

from torch import nn
pt_predictions = nn.functional.softmax(pt_outputs.logits, dim=-1)
print(pt_predictions)
tensor([[0.0021, 0.0018, 0.0115, 0.2121, 0.7725],
        [0.2084, 0.1826, 0.1969, 0.1755, 0.2365]], grad_fn=)
``
</pt>
<tf>
🤗 Transformers provides a simple and unified way to load pretrained instances. This means you can load an [TFAutoModel] like you would load an [AutoTokenizer]. The only difference is selecting the correct [TFAutoModel] for the task. For text (or sequence) classification, you should load [TFAutoModelForSequenceClassification`]:

from transformers import TFAutoModelForSequenceClassification
model_name = "nlptown/bert-base-multilingual-uncased-sentiment"
tf_model = TFAutoModelForSequenceClassification.from_pretrained(model_name)

See the task summary for tasks supported by an [AutoModel] class.

Now pass your preprocessed batch of inputs directly to the model. You can pass the tensors as-is:

tf_outputs = tf_model(tf_batch)

The model outputs the final activations in the logits attribute. Apply the softmax function to the logits to retrieve the probabilities:

import tensorflow as tf
tf_predictions = tf.nn.softmax(tf_outputs.logits, axis=-1)
tf_predictions  # doctest: +IGNORE_RESULT

All 🤗 Transformers models (PyTorch or TensorFlow) output the tensors before the final activation
function (like softmax) because the final activation function is often fused with the loss. Model outputs are special dataclasses so their attributes are autocompleted in an IDE. The model outputs behave like a tuple or a dictionary (you can index with an integer, a slice or a string) in which case, attributes that are None are ignored.

Save a model

Once your model is fine-tuned, you can save it with its tokenizer using [PreTrainedModel.save_pretrained]:

pt_save_directory = "./pt_save_pretrained"
tokenizer.save_pretrained(pt_save_directory)  # doctest: +IGNORE_RESULT
pt_model.save_pretrained(pt_save_directory)

When you are ready to use the model again, reload it with [PreTrainedModel.from_pretrained]:

pt_model = AutoModelForSequenceClassification.from_pretrained("./pt_save_pretrained")
``
</pt>
<tf>
Once your model is fine-tuned, you can save it with its tokenizer using [TFPreTrainedModel.save_pretrained`]:

tf_save_directory = "./tf_save_pretrained"
tokenizer.save_pretrained(tf_save_directory)  # doctest: +IGNORE_RESULT
tf_model.save_pretrained(tf_save_directory)

When you are ready to use the model again, reload it with [TFPreTrainedModel.from_pretrained]:

tf_model = TFAutoModelForSequenceClassification.from_pretrained("./tf_save_pretrained")

One particularly cool 🤗 Transformers feature is the ability to save a model and reload it as either a PyTorch or TensorFlow model. The from_pt or from_tf parameter can convert the model from one framework to the other:

from transformers import AutoModel
tokenizer = AutoTokenizer.from_pretrained(tf_save_directory)
pt_model = AutoModelForSequenceClassification.from_pretrained(tf_save_directory, from_tf=True)
</pt>
<tf>py
from transformers import TFAutoModel
tokenizer = AutoTokenizer.from_pretrained(pt_save_directory)
tf_model = TFAutoModelForSequenceClassification.from_pretrained(pt_save_directory, from_pt=True)

Custom model builds
You can modify the model's configuration class to change how a model is built. The configuration specifies a model's attributes, such as the number of hidden layers or attention heads. You start from scratch when you initialize a model from a custom configuration class. The model attributes are randomly initialized, and you'll need to train the model before you can use it to get meaningful results.
Start by importing [AutoConfig], and then load the pretrained model you want to modify. Within [AutoConfig.from_pretrained], you can specify the attribute you want to change, such as the number of attention heads:

from transformers import AutoConfig
my_config = AutoConfig.from_pretrained("distilbert-base-uncased", n_heads=12)

Create a model from your custom configuration with [AutoModel.from_config]:

from transformers import AutoModel
my_model = AutoModel.from_config(my_config)
``
</pt>
<tf>
Create a model from your custom configuration with [TFAutoModel.from_config`]:

from transformers import TFAutoModel
my_model = TFAutoModel.from_config(my_config)

Take a look at the Create a custom architecture guide for more information about building custom configurations.
Trainer - a PyTorch optimized training loop
All models are a standard torch.nn.Module so you can use them in any typical training loop. While you can write your own training loop, 🤗 Transformers provides a [Trainer] class for PyTorch, which contains the basic training loop and adds additional functionality for features like distributed training, mixed precision, and more.
Depending on your task, you'll typically pass the following parameters to [Trainer]:

You'll start with a [PreTrainedModel] or a torch.nn.Module:

from transformers import AutoModelForSequenceClassification
model = AutoModelForSequenceClassification.from_pretrained("distilbert-base-uncased")
   

[TrainingArguments] contains the model hyperparameters you can change like learning rate, batch size, and the number of epochs to train for. The default values are used if you don't specify any training arguments:

from transformers import TrainingArguments
training_args = TrainingArguments(
        output_dir="path/to/save/folder/",
        learning_rate=2e-5,
        per_device_train_batch_size=8,
        per_device_eval_batch_size=8,
        num_train_epochs=2,
    )
   

Load a preprocessing class like a tokenizer, image processor, feature extractor, or processor:

from transformers import AutoTokenizer
tokenizer = AutoTokenizer.from_pretrained("distilbert-base-uncased")
   

Load a dataset:

from datasets import load_dataset
dataset = load_dataset("rotten_tomatoes")  # doctest: +IGNORE_RESULT
   

Create a function to tokenize the dataset:

def tokenize_dataset(dataset):
        return tokenizer(dataset["text"])
   

Then apply it over the entire dataset with [~datasets.Dataset.map]:

dataset = dataset.map(tokenize_dataset, batched=True)
   

A [DataCollatorWithPadding] to create a batch of examples from your dataset:

from transformers import DataCollatorWithPadding
data_collator = DataCollatorWithPadding(tokenizer=tokenizer)
   

Now gather all these classes in [Trainer]:

from transformers import Trainer
trainer = Trainer(
     model=model,
     args=training_args,
     train_dataset=dataset["train"],
     eval_dataset=dataset["test"],
     tokenizer=tokenizer,
     data_collator=data_collator,
 )  # doctest: +SKIP

When you're ready, call [~Trainer.train] to start training:

trainer.train()  # doctest: +SKIP

For tasks - like translation or summarization - that use a sequence-to-sequence model, use the [Seq2SeqTrainer] and [Seq2SeqTrainingArguments] classes instead.

You can customize the training loop behavior by subclassing the methods inside [Trainer]. This allows you to customize features such as the loss function, optimizer, and scheduler. Take a look at the [Trainer] reference for which methods can be subclassed. 
The other way to customize the training loop is by using Callbacks. You can use callbacks to integrate with other libraries and inspect the training loop to report on progress or stop the training early. Callbacks do not modify anything in the training loop itself. To customize something like the loss function, you need to subclass the [Trainer] instead.
Train with TensorFlow
All models are a standard tf.keras.Model so they can be trained in TensorFlow with the Keras API. 🤗 Transformers provides the [~TFPreTrainedModel.prepare_tf_dataset] method to easily load your dataset as a tf.data.Dataset so you can start training right away with Keras' compile and fit methods.

You'll start with a [TFPreTrainedModel] or a tf.keras.Model:

from transformers import TFAutoModelForSequenceClassification
model = TFAutoModelForSequenceClassification.from_pretrained("distilbert-base-uncased")
   

Load a preprocessing class like a tokenizer, image processor, feature extractor, or processor:

from transformers import AutoTokenizer
tokenizer = AutoTokenizer.from_pretrained("distilbert-base-uncased")
   

Create a function to tokenize the dataset:

def tokenize_dataset(dataset):
        return tokenizer(dataset["text"])  # doctest: +SKIP
   

Apply the tokenizer over the entire dataset with [~datasets.Dataset.map] and then pass the dataset and tokenizer to [~TFPreTrainedModel.prepare_tf_dataset]. You can also change the batch size and shuffle the dataset here if you'd like:

dataset = dataset.map(tokenize_dataset)  # doctest: +SKIP
tf_dataset = model.prepare_tf_dataset(
        dataset["train"], batch_size=16, shuffle=True, tokenizer=tokenizer
    )  # doctest: +SKIP
   

When you're ready, you can call compile and fit to start training. Note that Transformers models all have a default task-relevant loss function, so you don't need to specify one unless you want to:

from tensorflow.keras.optimizers import Adam
model.compile(optimizer=Adam(3e-5))  # No loss argument!
model.fit(tf_dataset)  # doctest: +SKIP
   

What's next?
Now that you've completed the 🤗 Transformers quick tour, check out our guides and learn how to do more specific things like writing a custom model, fine-tuning a model for a task, and how to train a model with a script. If you're interested in learning more about 🤗 Transformers core concepts, grab a cup of coffee and take a look at our Conceptual Guides!