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.venv/Lib/site-packages/pandas/tests/io/parser/test_dialect.py

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+"""
+Tests that dialects are properly handled during parsing
+for all of the parsers defined in parsers.py
+"""
+
+import csv
+from io import StringIO
+
+import pytest
+
+from pandas.errors import ParserWarning
+
+from pandas import DataFrame
+import pandas._testing as tm
+
+pytestmark = pytest.mark.usefixtures("pyarrow_skip")
+
+
+@pytest.fixture
+def custom_dialect():
+    dialect_name = "weird"
+    dialect_kwargs = {
+        "doublequote": False,
+        "escapechar": "~",
+        "delimiter": ":",
+        "skipinitialspace": False,
+        "quotechar": "~",
+        "quoting": 3,
+    }
+    return dialect_name, dialect_kwargs
+
+
+def test_dialect(all_parsers):
+    parser = all_parsers
+    data = """\
+label1,label2,label3
+index1,"a,c,e
+index2,b,d,f
+"""
+
+    dia = csv.excel()
+    dia.quoting = csv.QUOTE_NONE
+    df = parser.read_csv(StringIO(data), dialect=dia)
+
+    data = """\
+label1,label2,label3
+index1,a,c,e
+index2,b,d,f
+"""
+    exp = parser.read_csv(StringIO(data))
+    exp.replace("a", '"a', inplace=True)
+    tm.assert_frame_equal(df, exp)
+
+
+def test_dialect_str(all_parsers):
+    dialect_name = "mydialect"
+    parser = all_parsers
+    data = """\
+fruit:vegetable
+apple:broccoli
+pear:tomato
+"""
+    exp = DataFrame({"fruit": ["apple", "pear"], "vegetable": ["broccoli", "tomato"]})
+
+    with tm.with_csv_dialect(dialect_name, delimiter=":"):
+        df = parser.read_csv(StringIO(data), dialect=dialect_name)
+        tm.assert_frame_equal(df, exp)
+
+
+def test_invalid_dialect(all_parsers):
+    class InvalidDialect:
+        pass
+
+    data = "a\n1"
+    parser = all_parsers
+    msg = "Invalid dialect"
+
+    with pytest.raises(ValueError, match=msg):
+        parser.read_csv(StringIO(data), dialect=InvalidDialect)
+
+
+@pytest.mark.parametrize(
+    "arg",
+    [None, "doublequote", "escapechar", "skipinitialspace", "quotechar", "quoting"],
+)
+@pytest.mark.parametrize("value", ["dialect", "default", "other"])
+def test_dialect_conflict_except_delimiter(all_parsers, custom_dialect, arg, value):
+    # see gh-23761.
+    dialect_name, dialect_kwargs = custom_dialect
+    parser = all_parsers
+
+    expected = DataFrame({"a": [1], "b": [2]})
+    data = "a:b\n1:2"
+
+    warning_klass = None
+    kwds = {}
+
+    # arg=None tests when we pass in the dialect without any other arguments.
+    if arg is not None:
+        if "value" == "dialect":  # No conflict --> no warning.
+            kwds[arg] = dialect_kwargs[arg]
+        elif "value" == "default":  # Default --> no warning.
+            from pandas.io.parsers.base_parser import parser_defaults
+
+            kwds[arg] = parser_defaults[arg]
+        else:  # Non-default + conflict with dialect --> warning.
+            warning_klass = ParserWarning
+            kwds[arg] = "blah"
+
+    with tm.with_csv_dialect(dialect_name, **dialect_kwargs):
+        with tm.assert_produces_warning(warning_klass):
+            result = parser.read_csv(StringIO(data), dialect=dialect_name, **kwds)
+            tm.assert_frame_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "kwargs,warning_klass",
+    [
+        ({"sep": ","}, None),  # sep is default --> sep_override=True
+        ({"sep": "."}, ParserWarning),  # sep isn't default --> sep_override=False
+        ({"delimiter": ":"}, None),  # No conflict
+        ({"delimiter": None}, None),  # Default arguments --> sep_override=True
+        ({"delimiter": ","}, ParserWarning),  # Conflict
+        ({"delimiter": "."}, ParserWarning),  # Conflict
+    ],
+    ids=[
+        "sep-override-true",
+        "sep-override-false",
+        "delimiter-no-conflict",
+        "delimiter-default-arg",
+        "delimiter-conflict",
+        "delimiter-conflict2",
+    ],
+)
+def test_dialect_conflict_delimiter(all_parsers, custom_dialect, kwargs, warning_klass):
+    # see gh-23761.
+    dialect_name, dialect_kwargs = custom_dialect
+    parser = all_parsers
+
+    expected = DataFrame({"a": [1], "b": [2]})
+    data = "a:b\n1:2"
+
+    with tm.with_csv_dialect(dialect_name, **dialect_kwargs):
+        with tm.assert_produces_warning(warning_klass):
+            result = parser.read_csv(StringIO(data), dialect=dialect_name, **kwargs)
+            tm.assert_frame_equal(result, expected)