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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:
- def test_concat_invalid(self):
- # trying to concat a ndframe with a non-ndframe
- df1 = tm.makeCustomDataframe(10, 2)
- for obj in [1, {}, [1, 2], (1, 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 = tm.makeCustomDataframe(10, 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.rand(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)
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