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from io import StringIO
import numpy as np
import pytest
from pandas import (
DataFrame,
concat,
read_csv,
)
import pandas._testing as tm
class TestInvalidConcat:
@pytest.mark.parametrize("obj", [1, {}, [1, 2], (1, 2)])
def test_concat_invalid(self, obj):
# trying to concat a ndframe with a non-ndframe
df1 = DataFrame(range(2))
msg = (
f"cannot concatenate object of type '{type(obj)}'; "
"only Series and DataFrame objs are valid"
)
with pytest.raises(TypeError, match=msg):
concat([df1, obj])
def test_concat_invalid_first_argument(self):
df1 = DataFrame(range(2))
msg = (
"first argument must be an iterable of pandas "
'objects, you passed an object of type "DataFrame"'
)
with pytest.raises(TypeError, match=msg):
concat(df1)
def test_concat_generator_obj(self):
# generator ok though
concat(DataFrame(np.random.default_rng(2).random((5, 5))) for _ in range(3))
def test_concat_textreader_obj(self):
# text reader ok
# GH6583
data = """index,A,B,C,D
foo,2,3,4,5
bar,7,8,9,10
baz,12,13,14,15
qux,12,13,14,15
foo2,12,13,14,15
bar2,12,13,14,15
"""
with read_csv(StringIO(data), chunksize=1) as reader:
result = concat(reader, ignore_index=True)
expected = read_csv(StringIO(data))
tm.assert_frame_equal(result, expected)