python/pyarrow/tests/test_builder.py

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import numpy as np

import pyarrow as pa
from pyarrow.lib import StringBuilder


def test_string_builder_append():
    sbuilder = StringBuilder()
    sbuilder.append(b"a byte string")
    sbuilder.append("a string")
    sbuilder.append(np.nan)
    sbuilder.append(None)
    assert len(sbuilder) == 4
    assert sbuilder.null_count == 2
    arr = sbuilder.finish()
    assert len(sbuilder) == 0
    assert isinstance(arr, pa.Array)
    assert arr.null_count == 2
    assert arr.type == 'str'
    expected = ["a byte string", "a string", None, None]
    assert arr.to_pylist() == expected


def test_string_builder_append_values():
    sbuilder = StringBuilder()
    sbuilder.append_values([np.nan, None, "text", None, "other text"])
    assert sbuilder.null_count == 3
    arr = sbuilder.finish()
    assert arr.null_count == 3
    expected = [None, None, "text", None, "other text"]
    assert arr.to_pylist() == expected


def test_string_builder_append_after_finish():
    sbuilder = StringBuilder()
    sbuilder.append_values([np.nan, None, "text", None, "other text"])
    arr = sbuilder.finish()
    sbuilder.append("No effect")
    expected = [None, None, "text", None, "other text"]
    assert arr.to_pylist() == expected