DEP: Deprecate passing a DataFrame to from_records (#51697)

Author: phofl

doc/source/whatsnew/v2.1.0.rst

@@ -93,6 +93,7 @@ Other API changes
 Deprecations
 ~~~~~~~~~~~~
 - Deprecating pinning ``group.name`` to each group in :meth:`SeriesGroupBy.aggregate` aggregations; if your operation requires utilizing the groupby keys, iterate over the groupby object instead (:issue:`41090`)
+- Deprecated passing a :class:`DataFrame` to :meth:`DataFrame.from_records`, use :meth:`DataFrame.set_index` or :meth:`DataFrame.drop` instead (:issue:`51353`)
 - Deprecated accepting slices in :meth:`DataFrame.take`, call ``obj[slicer]`` or pass a sequence of integers instead (:issue:`51539`)
 -
 

pandas/core/frame.py

@@ -2109,6 +2109,9 @@ def from_records(
  ----------
  data : structured ndarray, sequence of tuples or dicts, or DataFrame
  Structured input data.
+
+ .. deprecated:: 2.1.0
+ Passing a DataFrame is deprecated.
  index : str, list of fields, array-like
  Field of array to use as the index, alternately a specific set of
  input labels to use.
@@ -2171,6 +2174,23 @@ def from_records(
  2 1 c
  3 0 d
  """
+ if isinstance(data, DataFrame):
+ warnings.warn(
+ "Passing a DataFrame to DataFrame.from_records is deprecated. Use "
+ "set_index and/or drop to modify the DataFrame instead.",
+ FutureWarning,
+ stacklevel=find_stack_level(),
+ )
+ if columns is not None:
+ if is_scalar(columns):
+ columns = [columns]
+ data = data[columns]
+ if index is not None:
+ data = data.set_index(index)
+ if exclude is not None:
+ data = data.drop(columns=exclude)
+ return data
+
  result_index = None
 
  # Make a copy of the input columns so we can modify it
@@ -2238,7 +2258,7 @@ def maybe_reorder(
  arrays, arr_columns, columns, index
  )
 
- elif isinstance(data, (np.ndarray, DataFrame)):
+ elif isinstance(data, np.ndarray):
  arrays, columns = to_arrays(data, columns)
  arr_columns = columns
  else:

pandas/core/internals/construction.py

@@ -769,19 +769,6 @@ def to_arrays(
  -----
  Ensures that len(result_arrays) == len(result_index).
  """
- if isinstance(data, ABCDataFrame):
- # see test_from_records_with_index_data, test_from_records_bad_index_column
- if columns is not None:
- arrays = [
- data._ixs(i, axis=1)._values
- for i, col in enumerate(data.columns)
- if col in columns
- ]
- else:
- columns = data.columns
- arrays = [data._ixs(i, axis=1)._values for i in range(len(columns))]
-
- return arrays, columns
 
  if not len(data):
  if isinstance(data, np.ndarray):

pandas/tests/frame/constructors/test_from_records.py

@@ -25,7 +25,8 @@ def test_from_records_dt64tz_frame(self):
  # GH#51162 don't lose tz when calling from_records with DataFrame input
  dti = date_range("2016-01-01", periods=10, tz="US/Pacific")
  df = DataFrame({i: dti for i in range(4)})
- res = DataFrame.from_records(df)
+ with tm.assert_produces_warning(FutureWarning):
+ res = DataFrame.from_records(df)
  tm.assert_frame_equal(res, df)
 
  def test_from_records_with_datetimes(self):
@@ -177,29 +178,34 @@ def test_from_records_with_index_data(self):
  df = DataFrame(np.random.randn(10, 3), columns=["A", "B", "C"])
 
  data = np.random.randn(10)
- df1 = DataFrame.from_records(df, index=data)
+ with tm.assert_produces_warning(FutureWarning):
+ df1 = DataFrame.from_records(df, index=data)
  tm.assert_index_equal(df1.index, Index(data))
 
  def test_from_records_bad_index_column(self):
  df = DataFrame(np.random.randn(10, 3), columns=["A", "B", "C"])
 
  # should pass
- df1 = DataFrame.from_records(df, index=["C"])
+ with tm.assert_produces_warning(FutureWarning):
+ df1 = DataFrame.from_records(df, index=["C"])
  tm.assert_index_equal(df1.index, Index(df.C))
 
- df1 = DataFrame.from_records(df, index="C")
+ with tm.assert_produces_warning(FutureWarning):
+ df1 = DataFrame.from_records(df, index="C")
  tm.assert_index_equal(df1.index, Index(df.C))
 
  # should fail
  msg = "|".join(
  [
- r"Length of values \(10\) does not match length of index \(1\)",
+ r"'None of \[2\] are in the columns'",
  ]
  )
- with pytest.raises(ValueError, match=msg):
- DataFrame.from_records(df, index=[2])
- with pytest.raises(KeyError, match=r"^2$"):
- DataFrame.from_records(df, index=2)
+ with pytest.raises(KeyError, match=msg):
+ with tm.assert_produces_warning(FutureWarning):
+ DataFrame.from_records(df, index=[2])
+ with pytest.raises(KeyError, match=msg):
+ with tm.assert_produces_warning(FutureWarning):
+ DataFrame.from_records(df, index=2)
 
  def test_from_records_non_tuple(self):
  class Record: