# GPTC

General-purpose text classifier in Python

GPTC provides both a CLI tool and a Python library.

## Installation

    pip install gptc

## CLI Tool

### Classifying text

    gptc classify [-n <max_ngram_length>] <compiled model file>

This will prompt for a string and classify it, then print (in JSON) a dict of
the format `{category: probability, category:probability, ...}` to stdout. (For
information about `-n <max_ngram_length>`, see section "Ngrams.")

Alternatively, if you only need the most likely category, you can use this:

    gptc classify [-n <max_ngram_length>] <-c|--category> <compiled model file>

This will prompt for a string and classify it, outputting the category on
stdout (or "None" if it cannot determine anything).

### Compiling models

    gptc compile [-n <max_ngram_length>] [-c <min_count>] <raw model file>

This will print the compiled model encoded in binary format to stdout.

If `-c` is specified, words and ngrams used less than `min_count` times will be
excluded from the compiled model.

### Packing models

    gptc pack <dir>

This will print the raw model in JSON to stdout. See `models/unpacked/` for an
example of the format. Any exceptions will be printed to stderr.

## Library

### `Model.serialize()`

Returns a `bytes` representing the model.

### `gptc.deserialize(encoded_model)`

Deserialize a `Model` from a `bytes` returned by `Model.serialize()`.

### `Model.confidence(text, max_ngram_length)`

Classify `text`. Returns a dict of the format `{category: probability,
category:probability, ...}`

Note that this may not include values for all categories. If there are no
common words between the input and the training data (likely, for example, with
input in a different language from the training data), an empty dict will be
returned.

For information about `max_ngram_length`, see section "Ngrams."

### `Model.get(token)`

Return a confidence dict for the given token or ngram. This function is very
similar to `Model.confidence()`, except it treats the input as a single token
or ngram.

### `gptc.compile(raw_model, max_ngram_length=1, min_count=1)`

Compile a raw model (as a list, not JSON) and return the compiled model (as a
`gptc.Model` object).

For information about `max_ngram_length`, see section "Ngrams."

Words or ngrams used less than `min_count` times throughout the input text are
excluded from the model.

### `gptc.pack(directory, print_exceptions=False)`

Pack the model in `directory` and return a tuple of the format:

    (raw_model, [(exception,),(exception,)...])

Note that the exceptions are contained in single-item tuples. This is to allow
more information to be provided without breaking the API in future versions of
GPTC.

See `models/unpacked/` for an example of the format.

### `gptc.Classifier(model, max_ngram_length=1)`

`Classifier` objects are deprecated starting with GPTC 3.1.0, and will be
removed in 4.0.0. See [the README from
3.0.2](https://git.kj7rrv.com/kj7rrv/gptc/src/tag/v3.0.1/README.md) if you need
documentation.

## Ngrams

GPTC optionally supports using ngrams to improve classification accuracy. They
are disabled by default (maximum length set to 1) for performance reasons.
Enabling them significantly increases the time required both for compilation
and classification. The effect seems more significant for compilation than for
classification. Compiled models are also much larger when ngrams are enabled.
Larger maximum ngram lengths will result in slower performance and larger
files. It is a good idea to experiment with different values and use the
highest one at which GPTC is fast enough and models are small enough for your
needs.

Once a model is compiled at a certain maximum ngram length, it cannot be used
for classification with a higher value. If you instantiate a `Classifier` with
a model compiled with a lower `max_ngram_length`, the value will be silently
reduced to the one used when compiling the model.

## Model format

This section explains the raw model format, which is how models are created and
edited.

Raw models are formatted as a list of dicts. See below for the format:

    [
        {
            "text": "<text in the category>",
            "category": "<the category>"
        }
    ]

GPTC handles raw models as `list`s of `dict`s of `str`s (`List[Dict[str,
str]]`), and they can be stored in any way these Python objects can be.
However, it is recommended to store them in JSON format for compatibility with
the command-line tool.

## Emoji

GPTC treats individual emoji as words.

## Example model

An example model, which is designed to distinguish between texts written by
Mark Twain and those written by William Shakespeare, is available in `models`.
The raw model is in `models/raw.json`; the compiled model is in
`models/compiled.json`.

The example model was compiled with `max_ngram_length=10`.

## Benchmark

A benchmark script is available for comparing performance of GPTC between
different Python versions. To use it, run `benchmark.py` with all of the Python
installations you want to test. It tests both compilation and classification.
It uses the default Twain/Shakespeare model for both, and for classification it
uses [Mark Antony's "Friends, Romans, countrymen"
speech](https://en.wikipedia.org/wiki/Friends,_Romans,_countrymen,_lend_me_your_ears)
from Shakespeare's *Julius Caesar*.