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"""
Tests that comments are properly handled during parsing
for all of the parsers defined in parsers.py
"""
from io import StringIO
import numpy as np
import pytest
from pandas import DataFrame
import pandas._testing as tm
@pytest.mark.parametrize("na_values", [None, ["NaN"]])
def test_comment(all_parsers, na_values):
parser = all_parsers
data = """A,B,C
1,2.,4.#hello world
5.,NaN,10.0
"""
expected = DataFrame(
[[1.0, 2.0, 4.0], [5.0, np.nan, 10.0]], columns=["A", "B", "C"]
)
if parser.engine == "pyarrow":
msg = "The 'comment' option is not supported with the 'pyarrow' engine"
with pytest.raises(ValueError, match=msg):
parser.read_csv(StringIO(data), comment="#", na_values=na_values)
return
result = parser.read_csv(StringIO(data), comment="#", na_values=na_values)
tm.assert_frame_equal(result, expected)
@pytest.mark.parametrize(
"read_kwargs", [{}, {"lineterminator": "*"}, {"delim_whitespace": True}]
)
def test_line_comment(all_parsers, read_kwargs, request):
parser = all_parsers
data = """# empty
A,B,C
1,2.,4.#hello world
#ignore this line
5.,NaN,10.0
"""
warn = None
depr_msg = "The 'delim_whitespace' keyword in pd.read_csv is deprecated"
if read_kwargs.get("delim_whitespace"):
data = data.replace(",", " ")
warn = FutureWarning
elif read_kwargs.get("lineterminator"):
data = data.replace("\n", read_kwargs.get("lineterminator"))
read_kwargs["comment"] = "#"
if parser.engine == "pyarrow":
if "lineterminator" in read_kwargs:
msg = (
"The 'lineterminator' option is not supported with the 'pyarrow' engine"
)
else:
msg = "The 'comment' option is not supported with the 'pyarrow' engine"
with pytest.raises(ValueError, match=msg):
with tm.assert_produces_warning(
warn, match=depr_msg, check_stacklevel=False
):
parser.read_csv(StringIO(data), **read_kwargs)
return
elif parser.engine == "python" and read_kwargs.get("lineterminator"):
msg = r"Custom line terminators not supported in python parser \(yet\)"
with pytest.raises(ValueError, match=msg):
with tm.assert_produces_warning(
warn, match=depr_msg, check_stacklevel=False
):
parser.read_csv(StringIO(data), **read_kwargs)
return
with tm.assert_produces_warning(warn, match=depr_msg, check_stacklevel=False):
result = parser.read_csv(StringIO(data), **read_kwargs)
expected = DataFrame(
[[1.0, 2.0, 4.0], [5.0, np.nan, 10.0]], columns=["A", "B", "C"]
)
tm.assert_frame_equal(result, expected)
def test_comment_skiprows(all_parsers):
parser = all_parsers
data = """# empty
random line
# second empty line
1,2,3
A,B,C
1,2.,4.
5.,NaN,10.0
"""
# This should ignore the first four lines (including comments).
expected = DataFrame(
[[1.0, 2.0, 4.0], [5.0, np.nan, 10.0]], columns=["A", "B", "C"]
)
if parser.engine == "pyarrow":
msg = "The 'comment' option is not supported with the 'pyarrow' engine"
with pytest.raises(ValueError, match=msg):
parser.read_csv(StringIO(data), comment="#", skiprows=4)
return
result = parser.read_csv(StringIO(data), comment="#", skiprows=4)
tm.assert_frame_equal(result, expected)
def test_comment_header(all_parsers):
parser = all_parsers
data = """# empty
# second empty line
1,2,3
A,B,C
1,2.,4.
5.,NaN,10.0
"""
# Header should begin at the second non-comment line.
expected = DataFrame(
[[1.0, 2.0, 4.0], [5.0, np.nan, 10.0]], columns=["A", "B", "C"]
)
if parser.engine == "pyarrow":
msg = "The 'comment' option is not supported with the 'pyarrow' engine"
with pytest.raises(ValueError, match=msg):
parser.read_csv(StringIO(data), comment="#", header=1)
return
result = parser.read_csv(StringIO(data), comment="#", header=1)
tm.assert_frame_equal(result, expected)
def test_comment_skiprows_header(all_parsers):
parser = all_parsers
data = """# empty
# second empty line
# third empty line
X,Y,Z
1,2,3
A,B,C
1,2.,4.
5.,NaN,10.0
"""
# Skiprows should skip the first 4 lines (including comments),
# while header should start from the second non-commented line,
# starting with line 5.
expected = DataFrame(
[[1.0, 2.0, 4.0], [5.0, np.nan, 10.0]], columns=["A", "B", "C"]
)
if parser.engine == "pyarrow":
msg = "The 'comment' option is not supported with the 'pyarrow' engine"
with pytest.raises(ValueError, match=msg):
parser.read_csv(StringIO(data), comment="#", skiprows=4, header=1)
return
result = parser.read_csv(StringIO(data), comment="#", skiprows=4, header=1)
tm.assert_frame_equal(result, expected)
@pytest.mark.parametrize("comment_char", ["#", "~", "&", "^", "*", "@"])
def test_custom_comment_char(all_parsers, comment_char):
parser = all_parsers
data = "a,b,c\n1,2,3#ignore this!\n4,5,6#ignorethistoo"
if parser.engine == "pyarrow":
msg = "The 'comment' option is not supported with the 'pyarrow' engine"
with pytest.raises(ValueError, match=msg):
parser.read_csv(
StringIO(data.replace("#", comment_char)), comment=comment_char
)
return
result = parser.read_csv(
StringIO(data.replace("#", comment_char)), comment=comment_char
)
expected = DataFrame([[1, 2, 3], [4, 5, 6]], columns=["a", "b", "c"])
tm.assert_frame_equal(result, expected)
@pytest.mark.parametrize("header", ["infer", None])
def test_comment_first_line(all_parsers, header):
# see gh-4623
parser = all_parsers
data = "# notes\na,b,c\n# more notes\n1,2,3"
if header is None:
expected = DataFrame({0: ["a", "1"], 1: ["b", "2"], 2: ["c", "3"]})
else:
expected = DataFrame([[1, 2, 3]], columns=["a", "b", "c"])
if parser.engine == "pyarrow":
msg = "The 'comment' option is not supported with the 'pyarrow' engine"
with pytest.raises(ValueError, match=msg):
parser.read_csv(StringIO(data), comment="#", header=header)
return
result = parser.read_csv(StringIO(data), comment="#", header=header)
tm.assert_frame_equal(result, expected)
def test_comment_char_in_default_value(all_parsers, request):
# GH#34002
if all_parsers.engine == "c":
reason = "see gh-34002: works on the python engine but not the c engine"
# NA value containing comment char is interpreted as comment
request.applymarker(pytest.mark.xfail(reason=reason, raises=AssertionError))
parser = all_parsers
data = (
"# this is a comment\n"
"col1,col2,col3,col4\n"
"1,2,3,4#inline comment\n"
"4,5#,6,10\n"
"7,8,#N/A,11\n"
)
if parser.engine == "pyarrow":
msg = "The 'comment' option is not supported with the 'pyarrow' engine"
with pytest.raises(ValueError, match=msg):
parser.read_csv(StringIO(data), comment="#", na_values="#N/A")
return
result = parser.read_csv(StringIO(data), comment="#", na_values="#N/A")
expected = DataFrame(
{
"col1": [1, 4, 7],
"col2": [2, 5, 8],
"col3": [3.0, np.nan, np.nan],
"col4": [4.0, np.nan, 11.0],
}
)
tm.assert_frame_equal(result, expected)