SQuAD data source (#382)

Summary:
Pull Request resolved: #382

Data source specifically for the SQuAD 2.0 dataset.

Differential Revision: D14072144

fbshipit-source-id: 7e9765d1fa8e52a1ea641c50d7c97f59eacfc8d3

pytext/data/sources/squad.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
+import json
+from typing import List, Optional
+
+from pytext.data import types
+from pytext.data.sources.data_source import DataSource, generator_property
+
+
+def flatten(fname, ignore_impossible):
+    if not fname:
+        return
+    with open(fname) as file:
+        dump = json.load(file)
+    for article in dump["data"]:
+        for paragraph in article["paragraphs"]:
+            context = paragraph["context"]
+            for question in paragraph["qas"]:
+                label = not question["is_impossible"]
+                if label or not ignore_impossible:
+                    answers = (
+                        question["answers"] if label else question["plausible_answers"]
+                    )
+                    yield {
+                        "context": context,
+                        "question": question["question"],
+                        "answers": [answer["text"] for answer in answers],
+                        "answer_starts": [int(ans["answer_start"]) for ans in answers],
+                        "label": types.Label(label),
+                    }
+
+
+class SquadDataSource(DataSource):
+    """Download data from https://rajpurkar.github.io/SQuAD-explorer/
+       Will return tuples of (context, question, answer, answer_start, label, weight)
+    """
+
+    class Config(DataSource.Config):
+        train_filename: Optional[str] = "train-v2.0.json"
+        test_filename: Optional[str] = "dev-v2.0.json"
+        eval_filename: Optional[str] = "dev-v2.0.json"
+        ignore_impossible: bool = True
+
+    @classmethod
+    def from_config(cls, config: Config, schema=None):
+        return cls(
+            config.train_filename,
+            config.test_filename,
+            config.eval_filename,
+            config.ignore_impossible,
+        )
+
+    def __init__(
+        self,
+        train_filename=None,
+        test_filename=None,
+        eval_filename=None,
+        ignore_impossible=Config.ignore_impossible,
+    ):
+        schema = {
+            "context": str,
+            "question": str,
+            "answers": List[str],
+            "answer_starts": List[int],
+            "answer_ends": List[int],
+            "label": types.Label,
+        }
+        super().__init__(schema)
+        self.train_filename = train_filename
+        self.test_filename = test_filename
+        self.eval_filename = eval_filename
+        self.ignore_impossible = ignore_impossible
+
+    @generator_property
+    def train(self):
+        return flatten(self.train_filename, self.ignore_impossible)
+
+    @generator_property
+    def test(self):
+        return flatten(self.test_filename, self.ignore_impossible)
+
+    @generator_property
+    def eval(self):
+        return flatten(self.eval_filename, self.ignore_impossible)

pytext/data/types.py

@@ -31,3 +31,9 @@ class Label(DataType, str):
 
 class Text(DataType, str):
     """Human language text."""
+
+class Int(DataType, int):
+    """Int type."""
+
+class Float(DataType, float):
+    """Float type."""