openai/tiktoken

What it solves

tiktoken is a fast Byte Pair Encoding (BPE) tokenizer, designed specifically for use with OpenAI's models. It solves the problem of converting raw text into a sequence of numbers (tokens) that language models can process, ensuring the process is reversible, lossless, and efficient.

How it works

It uses Byte Pair Encoding (BPE), a method that converts text into tokens by identifying common subwords (e.g., "//"ing"" in "encoding"). This allows the model to better understand grammar and generalise. The library provides a simple API to get encodings for specific OpenAI models (like gpt-4o) or specific base encodings (like o200k_base).

Who it’s for

Developers building applications with OpenAI's models who need to accurately count tokens, encode text for model input, or decode tokens back into text.

Highlights

• High Performance: It is 3-6x faster than comparable open-source tokenizers.
• Extensible: Supports adding new encodings via custom Encoding objects or a plugin mechanism via tiktoken_ext.
• Educational Submodule: Includes a toolset for learning and visualizing the BPE procedure.
• Lossless Compression: Ensures that the token sequence is shorter than the original bytes while remaining fully reversible.