Source code for featuretools.primitives.standard.transform.natural_language.num_words

import re
from string import punctuation
from typing import Optional

import pandas as pd
from woodwork.column_schema import ColumnSchema
from woodwork.logical_types import IntegerNullable, NaturalLanguage

from featuretools.primitives.base import TransformPrimitive
from featuretools.primitives.standard.transform.natural_language.constants import (
    DELIMITERS,
)


class NumWords(TransformPrimitive):
    """Determines the number of words in a string. Words are sequences of characters
    delimited by whitespace.

    Examples:
        >>> num_words = NumWords()
        >>> num_words(['This is a string',
        ...            'Two words',
        ...            'no-spaces',
        ...            'Also works with sentences. Second sentence!']).tolist()
        [4, 2, 1, 6]
    """

    name = "num_words"
    input_types = [ColumnSchema(logical_type=NaturalLanguage)]
    return_type = ColumnSchema(logical_type=IntegerNullable, semantic_tags={"numeric"})

    description_template = "the number of words in {}"

    def get_function(self):
        def word_counter(array):
            def _get_number_of_words(elem: Optional[str]):
                """Returns the number of words in given element,
                or pd.NA given null input"""
                if pd.isna(elem):
                    return pd.NA
                return sum(
                    1 for word in re.split(DELIMITERS, elem) if word.strip(punctuation)
                )

            return array.apply(_get_number_of_words)

        return word_counter