### What changes were proposed in this pull request?
This PR proposes to migrate to [NumPy documentation style](https://numpydoc.readthedocs.io/en/latest/format.html), see also SPARK-33243.
While I am migrating, I also fixed some Python type hints accordingly.
### Why are the changes needed?
For better documentation as text itself, and generated HTMLs
### Does this PR introduce _any_ user-facing change?
Yes, they will see a better format of HTMLs, and better text format. See SPARK-33243.
### How was this patch tested?
Manually tested via running `./dev/lint-python`.
Closes#30181 from HyukjinKwon/SPARK-33250.
Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
https://issues.apache.org/jira/browse/SPARK-32719
### What changes were proposed in this pull request?
Add a check to detect missing imports. This makes sure that if we use a specific class, it should be explicitly imported (not using a wildcard).
### Why are the changes needed?
To make sure that the quality of the Python code is up to standard.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Existing unit-tests and Flake8 static analysis
Closes#29563 from Fokko/fd-add-check-missing-imports.
Authored-by: Fokko Driesprong <fokko@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
### What changes were proposed in this pull request?
This PR aims to drop Python 2.7, 3.4 and 3.5.
Roughly speaking, it removes all the widely known Python 2 compatibility workarounds such as `sys.version` comparison, `__future__`. Also, it removes the Python 2 dedicated codes such as `ArrayConstructor` in Spark.
### Why are the changes needed?
1. Unsupport EOL Python versions
2. Reduce maintenance overhead and remove a bit of legacy codes and hacks for Python 2.
3. PyPy2 has a critical bug that causes a flaky test, SPARK-28358 given my testing and investigation.
4. Users can use Python type hints with Pandas UDFs without thinking about Python version
5. Users can leverage one latest cloudpickle, https://github.com/apache/spark/pull/28950. With Python 3.8+ it can also leverage C pickle.
### Does this PR introduce _any_ user-facing change?
Yes, users cannot use Python 2.7, 3.4 and 3.5 in the upcoming Spark version.
### How was this patch tested?
Manually tested and also tested in Jenkins.
Closes#28957 from HyukjinKwon/SPARK-32138.
Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
### What changes were proposed in this pull request?
When you use floats are index of pandas, it creates a Spark DataFrame with a wrong results as below when Arrow is enabled:
```bash
./bin/pyspark --conf spark.sql.execution.arrow.pyspark.enabled=true
```
```python
>>> import pandas as pd
>>> spark.createDataFrame(pd.DataFrame({'a': [1,2,3]}, index=[2., 3., 4.])).show()
+---+
| a|
+---+
| 1|
| 1|
| 2|
+---+
```
This is because direct slicing uses the value as index when the index contains floats:
```python
>>> pd.DataFrame({'a': [1,2,3]}, index=[2., 3., 4.])[2:]
a
2.0 1
3.0 2
4.0 3
>>> pd.DataFrame({'a': [1,2,3]}, index=[2., 3., 4.]).iloc[2:]
a
4.0 3
>>> pd.DataFrame({'a': [1,2,3]}, index=[2, 3, 4])[2:]
a
4 3
```
This PR proposes to explicitly use `iloc` to positionally slide when we create a DataFrame from a pandas DataFrame with Arrow enabled.
FWIW, I was trying to investigate why direct slicing refers the index value or the positional index sometimes but I stopped investigating further after reading this https://pandas.pydata.org/pandas-docs/stable/getting_started/10min.html#selection
> While standard Python / Numpy expressions for selecting and setting are intuitive and come in handy for interactive work, for production code, we recommend the optimized pandas data access methods, `.at`, `.iat`, `.loc` and `.iloc`.
### Why are the changes needed?
To create the correct Spark DataFrame from a pandas DataFrame without a data loss.
### Does this PR introduce _any_ user-facing change?
Yes, it is a bug fix.
```bash
./bin/pyspark --conf spark.sql.execution.arrow.pyspark.enabled=true
```
```python
import pandas as pd
spark.createDataFrame(pd.DataFrame({'a': [1,2,3]}, index=[2., 3., 4.])).show()
```
Before:
```
+---+
| a|
+---+
| 1|
| 1|
| 2|
+---+
```
After:
```
+---+
| a|
+---+
| 1|
| 2|
| 3|
+---+
```
### How was this patch tested?
Manually tested and unittest were added.
Closes#28928 from HyukjinKwon/SPARK-32098.
Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: Bryan Cutler <cutlerb@gmail.com>
### What changes were proposed in this pull request?
This PR is adding support duplicated column names for `toPandas` with Arrow execution.
### Why are the changes needed?
When we execute `toPandas()` with Arrow execution, it fails if the column names have duplicates.
```py
>>> spark.sql("select 1 v, 1 v").toPandas()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/path/to/lib/python3.7/site-packages/pyspark/sql/dataframe.py", line 2132, in toPandas
pdf = table.to_pandas()
File "pyarrow/array.pxi", line 441, in pyarrow.lib._PandasConvertible.to_pandas
File "pyarrow/table.pxi", line 1367, in pyarrow.lib.Table._to_pandas
File "/path/to/lib/python3.7/site-packages/pyarrow/pandas_compat.py", line 653, in table_to_blockmanager
columns = _deserialize_column_index(table, all_columns, column_indexes)
File "/path/to/lib/python3.7/site-packages/pyarrow/pandas_compat.py", line 704, in _deserialize_column_index
columns = _flatten_single_level_multiindex(columns)
File "/path/to/lib/python3.7/site-packages/pyarrow/pandas_compat.py", line 937, in _flatten_single_level_multiindex
raise ValueError('Found non-unique column index')
ValueError: Found non-unique column index
```
### Does this PR introduce any user-facing change?
Yes, previously we will face an error above, but after this PR, we will see the result:
```py
>>> spark.sql("select 1 v, 1 v").toPandas()
v v
0 1 1
```
### How was this patch tested?
Added and modified related tests.
Closes#28210 from ueshin/issues/SPARK-31441/to_pandas.
Authored-by: Takuya UESHIN <ueshin@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
### What changes were proposed in this pull request?
When `toPandas` API works on duplicate column names produced from operators like join, we see the error like:
```
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
```
This patch fixes the error in `toPandas` API.
### Why are the changes needed?
To make `toPandas` work on dataframe with duplicate column names.
### Does this PR introduce any user-facing change?
Yes. Previously calling `toPandas` API on a dataframe with duplicate column names will fail. After this patch, it will produce correct result.
### How was this patch tested?
Unit test.
Closes#28025 from viirya/SPARK-31186.
Authored-by: Liang-Chi Hsieh <viirya@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
### What changes were proposed in this pull request?
Prevent unnecessary copies of data during conversion from Arrow to Pandas.
### Why are the changes needed?
During conversion of pyarrow data to Pandas, columns are checked for timestamp types and then modified to correct for local timezone. If the data contains no timestamp types, then unnecessary copies of the data can be made. This is most prevalent when checking columns of a pandas DataFrame where each series is assigned back to the DataFrame, regardless if it had timestamps. See https://www.mail-archive.com/devarrow.apache.org/msg17008.html and ARROW-7596 for discussion.
### Does this PR introduce any user-facing change?
No
### How was this patch tested?
Existing tests
Closes#27358 from BryanCutler/pyspark-pandas-timestamp-copy-fix-SPARK-30640.
Authored-by: Bryan Cutler <cutlerb@gmail.com>
Signed-off-by: Bryan Cutler <cutlerb@gmail.com>
### What changes were proposed in this pull request?
In the PR, I propose to remove the SQL config `spark.sql.execution.pandas.respectSessionTimeZone` which has been deprecated since Spark 2.3.
### Why are the changes needed?
To improve code maintainability.
### Does this PR introduce any user-facing change?
Yes.
### How was this patch tested?
by running python tests, https://spark.apache.org/docs/latest/building-spark.html#pyspark-tests-with-maven-or-sbtCloses#27218 from MaxGekk/remove-respectSessionTimeZone.
Authored-by: Maxim Gekk <max.gekk@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
### What changes were proposed in this pull request?
This is a followup of https://github.com/apache/spark/pull/27109. It should match the parameter lists in `createDataFrame`.
### Why are the changes needed?
To pass parameters supposed to pass.
### Does this PR introduce any user-facing change?
No (it's only in master)
### How was this patch tested?
Manually tested and existing tests should cover.
Closes#27225 from HyukjinKwon/SPARK-30434-followup.
Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
### What changes were proposed in this pull request?
This PR proposes to move pandas related functionalities into pandas package. Namely:
```bash
pyspark/sql/pandas
├── __init__.py
├── conversion.py # Conversion between pandas <> PySpark DataFrames
├── functions.py # pandas_udf
├── group_ops.py # Grouped UDF / Cogrouped UDF + groupby.apply, groupby.cogroup.apply
├── map_ops.py # Map Iter UDF + mapInPandas
├── serializers.py # pandas <> PyArrow serializers
├── types.py # Type utils between pandas <> PyArrow
└── utils.py # Version requirement checks
```
In order to separately locate `groupby.apply`, `groupby.cogroup.apply`, `mapInPandas`, `toPandas`, and `createDataFrame(pdf)` under `pandas` sub-package, I had to use a mix-in approach which Scala side uses often by `trait`, and also pandas itself uses this approach (see `IndexOpsMixin` as an example) to group related functionalities. Currently, you can think it's like Scala's self typed trait. See the structure below:
```python
class PandasMapOpsMixin(object):
def mapInPandas(self, ...):
...
return ...
# other Pandas <> PySpark APIs
```
```python
class DataFrame(PandasMapOpsMixin):
# other DataFrame APIs equivalent to Scala side.
```
Yes, This is a big PR but they are mostly just moving around except one case `createDataFrame` which I had to split the methods.
### Why are the changes needed?
There are pandas functionalities here and there and I myself gets lost where it was. Also, when you have to make a change commonly for all of pandas related features, it's almost impossible now.
Also, after this change, `DataFrame` and `SparkSession` become more consistent with Scala side since pandas is specific to Python, and this change separates pandas-specific APIs away from `DataFrame` or `SparkSession`.
### Does this PR introduce any user-facing change?
No.
### How was this patch tested?
Existing tests should cover. Also, I manually built the PySpark API documentation and checked.
Closes#27109 from HyukjinKwon/pandas-refactoring.
Authored-by: HyukjinKwon <gurwls223@apache.org>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
