From 5dd77866c28d1a95958628ba0412d1dfdb10f99b Mon Sep 17 00:00:00 2001
From: Venkat <87000728+kpvenkat47@users.noreply.github.com>
Date: Tue, 18 Mar 2025 19:25:39 +0530
Subject: [PATCH 1/4] Fix from records() to preserve columns when nrows=0
---
pandas/core/frame.py | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 8f65277f660f7..7ee8992e1c39d 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -2231,7 +2231,7 @@ def maybe_reorder(
if is_iterator(data):
if nrows == 0:
- return cls()
+ return cls(columns=columns)
try:
first_row = next(data)
From cc21929647532edd4eff03401c863cb33349cc09 Mon Sep 17 00:00:00 2001
From: kpvenkat47 <kpvenkat47@gmail.com>
Date: Tue, 18 Mar 2025 20:43:36 +0530
Subject: [PATCH 2/4] Update empty DataFrame initialization to preserve columns
- Changed 'if nrows == 0' to return Cls(columns=columns) in core/frame.py. -
Added test to verify column preservation.
---
pandas/core/frame.py | 2 +-
pandas/core/frame_test_constructors.py | 7 +++++++
2 files changed, 8 insertions(+), 1 deletion(-)
create mode 100644 pandas/core/frame_test_constructors.py
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 8f65277f660f7..7ee8992e1c39d 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -2231,7 +2231,7 @@ def maybe_reorder(
if is_iterator(data):
if nrows == 0:
- return cls()
+ return cls(columns=columns)
try:
first_row = next(data)
diff --git a/pandas/core/frame_test_constructors.py b/pandas/core/frame_test_constructors.py
new file mode 100644
index 0000000000000..b542c8b21ee79
--- /dev/null
+++ b/pandas/core/frame_test_constructors.py
@@ -0,0 +1,7 @@
+import pandas as pd
+def test_empty_df_preserve_col():
+ rows = []
+ df = pd.DataFrame.from_records(iter(rows), columns=['col_1', 'Col_2'], nrows=0)
+ assert list(df.columns)==['col_1', 'Col_2']
+ assert len(df) == 0
+
\ No newline at end of file
From e2fbcebd61b1bc5d68489b75e94bd3d0338c671a Mon Sep 17 00:00:00 2001
From: kpvenkat47 <kpvenkat47@gmail.com>
Date: Wed, 26 Mar 2025 18:50:40 +0530
Subject: [PATCH 3/4] Updated PR #6114 based on review feedback
---
pandas/tests/frame/test_constructors.py | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/pandas/tests/frame/test_constructors.py b/pandas/tests/frame/test_constructors.py
index 037a2ae294bb2..400a36305bb96 100644
--- a/pandas/tests/frame/test_constructors.py
+++ b/pandas/tests/frame/test_constructors.py
@@ -2780,6 +2780,12 @@ def test_construction_nan_value_timedelta64_dtype(self):
)
tm.assert_frame_equal(result, expected)
+ def test_from_records_empty_iterator_with_preserve_columns(self):
+
+ rows = []
+ df = pd.DataFrame.from_records(iter(rows), columns=["col_1", "Col_2"], nrows=0)
+ assert list(df.columns) == ["col_1", "Col_2"]
+ assert len(df) == 0
class TestDataFrameConstructorIndexInference:
def test_frame_from_dict_of_series_overlapping_monthly_period_indexes(self):
From 5dcc1ac81005c5139d86705d46f615cf45ee9bfc Mon Sep 17 00:00:00 2001
From: kpvenkat47 <kpvenkat47@gmail.com>
Date: Tue, 1 Apr 2025 18:43:54 +0530
Subject: [PATCH 4/4] All reviews are updated.Please check
---
pandas/core/frame_test_constructors.py | 7 -------
pandas/tests/frame/constructors/test_from_records.py | 8 ++++++++
pandas/tests/frame/test_constructors.py | 8 +-------
3 files changed, 9 insertions(+), 14 deletions(-)
delete mode 100644 pandas/core/frame_test_constructors.py
diff --git a/pandas/core/frame_test_constructors.py b/pandas/core/frame_test_constructors.py
deleted file mode 100644
index b542c8b21ee79..0000000000000
--- a/pandas/core/frame_test_constructors.py
+++ /dev/null
@@ -1,7 +0,0 @@
-import pandas as pd
-def test_empty_df_preserve_col():
- rows = []
- df = pd.DataFrame.from_records(iter(rows), columns=['col_1', 'Col_2'], nrows=0)
- assert list(df.columns)==['col_1', 'Col_2']
- assert len(df) == 0
-
\ No newline at end of file
diff --git a/pandas/tests/frame/constructors/test_from_records.py b/pandas/tests/frame/constructors/test_from_records.py
index 1d4a2c0075e3e..57bd7a3c877ea 100644
--- a/pandas/tests/frame/constructors/test_from_records.py
+++ b/pandas/tests/frame/constructors/test_from_records.py
@@ -492,3 +492,11 @@ def test_from_records_structured_array(self):
expected_result = DataFrame(modified_data)
tm.assert_frame_equal(actual_result, expected_result)
+
+
+ def test_from_records_empty_iterator_with_preserve_columns(self):
+ # GH#61140
+ rows = []
+ result = DataFrame.from_records(iter(rows), columns=["col_1", "Col_2"], nrows=0)
+ expected = DataFrame([],columns=["col_1", "Col_2"])
+ tm.assert_frame_equal(result, expected)
diff --git a/pandas/tests/frame/test_constructors.py b/pandas/tests/frame/test_constructors.py
index 400a36305bb96..18f0d4a864c04 100644
--- a/pandas/tests/frame/test_constructors.py
+++ b/pandas/tests/frame/test_constructors.py
@@ -2779,13 +2779,7 @@ def test_construction_nan_value_timedelta64_dtype(self):
["NaT", "0 days 00:00:00.000000001"], dtype="timedelta64[ns]"
)
tm.assert_frame_equal(result, expected)
-
- def test_from_records_empty_iterator_with_preserve_columns(self):
-
- rows = []
- df = pd.DataFrame.from_records(iter(rows), columns=["col_1", "Col_2"], nrows=0)
- assert list(df.columns) == ["col_1", "Col_2"]
- assert len(df) == 0
+
class TestDataFrameConstructorIndexInference:
def test_frame_from_dict_of_series_overlapping_monthly_period_indexes(self):