BUG: DataFrame.to_markdown with an empty frame (#38406)

Author: arw2019

ci/deps/azure-38.yaml

@@ -17,4 +17,4 @@ dependencies:
  - python-dateutil
  - nomkl
  - pytz
- - tabulate==0.8.3
+ - tabulate==0.8.7

doc/source/getting_started/install.rst

@@ -283,7 +283,7 @@ pyreadstat SPSS files (.sav) reading
 pyxlsb 1.0.6 Reading for xlsb files
 qtpy Clipboard I/O
 s3fs 0.4.0 Amazon S3 access
-tabulate 0.8.3 Printing in Markdown-friendly format (see `tabulate`_)
+tabulate 0.8.7 Printing in Markdown-friendly format (see `tabulate`_)
 xarray 0.12.3 pandas-like API for N-dimensional data
 xclip Clipboard I/O on linux
 xlrd 1.2.0 Excel reading

doc/source/whatsnew/v1.3.0.rst

@@ -37,7 +37,76 @@ These are bug fixes that might have notable behavior changes.
 
 Increased minimum versions for dependencies
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
+Some minimum supported versions of dependencies were updated.
+If installed, we now require:
+
++-----------------+-----------------+----------+---------+
+| Package | Minimum Version | Required | Changed |
++=================+=================+==========+=========+
+| numpy | 1.16.5 | X | |
++-----------------+-----------------+----------+---------+
+| pytz | 2017.3 | X | |
++-----------------+-----------------+----------+---------+
+| python-dateutil | 2.7.3 | X | |
++-----------------+-----------------+----------+---------+
+| bottleneck | 1.2.1 | | |
++-----------------+-----------------+----------+---------+
+| numexpr | 2.6.8 | | |
++-----------------+-----------------+----------+---------+
+| pytest (dev) | 5.0.1 | | |
++-----------------+-----------------+----------+---------+
+| mypy (dev) | 0.782 | | |
++-----------------+-----------------+----------+---------+
+
+For `optional libraries <https://dev.pandas.io/docs/install.html#dependencies>`_ the general recommendation is to use the latest version.
+The following table lists the lowest version per library that is currently being tested throughout the development of pandas.
+Optional libraries below the lowest tested version may still work, but are not considered supported.
+
++-----------------+-----------------+---------+
+| Package | Minimum Version | Changed |
++=================+=================+=========+
+| beautifulsoup4 | 4.6.0 | |
++-----------------+-----------------+---------+
+| fastparquet | 0.3.2 | |
++-----------------+-----------------+---------+
+| fsspec | 0.7.4 | |
++-----------------+-----------------+---------+
+| gcsfs | 0.6.0 | |
++-----------------+-----------------+---------+
+| lxml | 4.3.0 | |
++-----------------+-----------------+---------+
+| matplotlib | 2.2.3 | |
++-----------------+-----------------+---------+
+| numba | 0.46.0 | |
++-----------------+-----------------+---------+
+| openpyxl | 2.6.0 | |
++-----------------+-----------------+---------+
+| pyarrow | 0.15.0 | |
++-----------------+-----------------+---------+
+| pymysql | 0.7.11 | |
++-----------------+-----------------+---------+
+| pytables | 3.5.1 | |
++-----------------+-----------------+---------+
+| s3fs | 0.4.0 | |
++-----------------+-----------------+---------+
+| scipy | 1.2.0 | |
++-----------------+-----------------+---------+
+| sqlalchemy | 1.2.8 | |
++-----------------+-----------------+---------+
+| tabulate | 0.8.7 | X |
++-----------------+-----------------+---------+
+| xarray | 0.12.0 | |
++-----------------+-----------------+---------+
+| xlrd | 1.2.0 | |
++-----------------+-----------------+---------+
+| xlsxwriter | 1.0.2 | |
++-----------------+-----------------+---------+
+| xlwt | 1.3.0 | |
++-----------------+-----------------+---------+
+| pandas-gbq | 0.12.0 | |
++-----------------+-----------------+---------+
+
+See :ref:`install.dependencies` and :ref:`install.optional_dependencies` for more.
 
 .. _whatsnew_130.api.other:
 

pandas/compat/_optional.py

@@ -24,7 +24,7 @@
  "scipy": "1.2.0",
  "sqlalchemy": "1.2.8",
  "tables": "3.5.1",
- "tabulate": "0.8.3",
+ "tabulate": "0.8.7",
  "xarray": "0.12.3",
  "xlrd": "1.2.0",
  "xlwt": "1.3.0",

pandas/tests/io/formats/test_to_markdown.py

@@ -18,6 +18,17 @@ def test_simple():
  )
 
 
+def test_empty_frame():
+ buf = StringIO()
+ df = pd.DataFrame({"id": [], "first_name": [], "last_name": []}).set_index("id")
+ df.to_markdown(buf=buf)
+ result = buf.getvalue()
+ assert result == (
+ "| id | first_name | last_name |\n"
+ "|------|--------------|-------------|"
+ )
+
+
 def test_other_tablefmt():
  buf = StringIO()
  df = pd.DataFrame([1, 2, 3])