Merge pull request #3 from datapythonista/preview_docs

Preview docs

Author: datapythonista

.github/workflows/docbuild-and-upload.yml

@@ -89,3 +89,10 @@ jobs:
         name: website
         path: web/build
         retention-days: 14
+
+    - name: Trigger web/doc preview
+      run: curl -X POST https://pandas.pydata.org/preview/submit/$RUN_ID/$PR_ID/
+      env:
+        RUN_ID: ${{ github.run_id }}
+        PR_ID: ${{ github.event.pull_request.number }}
+      if: github.event_name == 'pull_request'

.github/workflows/preview-docs.yml

@@ -0,0 +1,22 @@
+name: Assign
+on:
+  issue_comment:
+    types: created
+
+permissions:
+  contents: read
+
+jobs:
+  issue_assign:
+    permissions:
+      issues: write
+      pull-requests: write
+    runs-on: ubuntu-22.04
+    steps:
+    - if: github.event.comment.body == '/preview'
+      run: |
+        if curl --output /dev/null --silent --head --fail "https://pandas.pydata.org/preview/${{ github.event.issue.number }}"; then
+          curl -H "Authorization: token ${{ secrets.GITHUB_TOKEN }}" -d '{"body": "Website preview of this PR available at: https://pandas.pydata.org/preview/${{ github.event.issue.number }}"}' https://api.github.com/repos/${{ github.repository }}/issues/${{ github.event.issue.number }}/comments
+        else
+          curl -H "Authorization: token ${{ secrets.GITHUB_TOKEN }}" -d '{"body": "No preview found for PR ${{ github.event.issue.number }}"}' https://api.github.com/repos/${{ github.repository }}/issues/${{ github.event.issue.number }}/comments
+        fi

doc/source/whatsnew/v2.0.0.rst

@@ -246,6 +246,10 @@ Copy-on-Write improvements
   a modification to the data happens) when constructing a Series from an existing
   Series with the default of ``copy=False`` (:issue:`50471`)
 
+- The :class:`DataFrame` constructor will now create a lazy copy (deferring the copy until
+  a modification to the data happens) when constructing from an existing
+  :class:`DataFrame` with the default of ``copy=False`` (:issue:`51239`)
+
 - The :class:`DataFrame` constructor, when constructing a DataFrame from a dictionary
   of Series objects and specifying ``copy=False``, will now use a lazy copy
   of those Series objects for the columns of the DataFrame (:issue:`50777`)

pandas/core/frame.py

@@ -656,6 +656,8 @@ def __init__(
                 data = data.copy(deep=False)
 
         if isinstance(data, (BlockManager, ArrayManager)):
+            if using_copy_on_write():
+                data = data.copy(deep=False)
             # first check if a Manager is passed without any other arguments
             # -> use fastpath (without checking Manager type)
             if index is None and columns is None and dtype is None and not copy:

pandas/tests/copy_view/test_constructors.py

@@ -82,6 +82,25 @@ def test_series_from_series_with_reindex(using_copy_on_write):
         assert not result._mgr.blocks[0].refs.has_reference()
 
 
+@pytest.mark.parametrize("func", [lambda x: x, lambda x: x._mgr])
+@pytest.mark.parametrize("columns", [None, ["a"]])
+def test_dataframe_constructor_mgr_or_df(using_copy_on_write, columns, func):
+    df = DataFrame({"a": [1, 2, 3]})
+    df_orig = df.copy()
+
+    new_df = DataFrame(func(df))
+
+    assert np.shares_memory(get_array(df, "a"), get_array(new_df, "a"))
+    new_df.iloc[0] = 100
+
+    if using_copy_on_write:
+        assert not np.shares_memory(get_array(df, "a"), get_array(new_df, "a"))
+        tm.assert_frame_equal(df, df_orig)
+    else:
+        assert np.shares_memory(get_array(df, "a"), get_array(new_df, "a"))
+        tm.assert_frame_equal(df, new_df)
+
+
 @pytest.mark.parametrize("dtype", [None, "int64", "Int64"])
 @pytest.mark.parametrize("index", [None, [0, 1, 2]])
 @pytest.mark.parametrize("columns", [None, ["a", "b"], ["a", "b", "c"]])