Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/18378#discussion_r123461244
--- Diff: python/pyspark/sql/dataframe.py ---
@@ -1721,7 +1721,18 @@ def toPandas(self):
1 5 Bob
"""
import pandas as pd
- return pd.DataFrame.from_records(self.collect(),
columns=self.columns)
+
+ dtype = {}
+ for field in self.schema:
+ pandas_type = _to_corrected_pandas_type(field.dataType)
+ if pandas_type is not None:
+ dtype[field.name] = pandas_type
+
+ pdf = pd.DataFrame.from_records(self.collect(),
columns=self.columns)
+
+ for f, t in dtype.items():
+ pdf[f] = pdf[f].astype(t, copy=False)
--- End diff --
Just, just in case someone blames this in the future, as a little side
note, it looks `copy` is introduced in 0.11.0
[here](https://github.com/pandas-dev/pandas/blob/v0.11.0/pandas/core/generic.py#L521).
So, Pandas 0.10.0 does not work with it (see
[here](https://github.com/pandas-dev/pandas/blob/v0.10.0/pandas/core/generic.py#L489)).
```python
from pyspark.sql.types import *
schema = StructType().add("a", IntegerType()).add("b", StringType())\
.add("c", BooleanType()).add("d", FloatType())
data = [
(1, "foo", True, 3.0,), (2, "foo", True, 5.0),
(3, "bar", False, -1.0), (4, "bar", False, 6.0),
]
spark.createDataFrame(data, schema).toPandas().dtypes
```
Pandas 0.10.0:
```
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File
"/Users/hyukjinkwon/Desktop/workspace/repos/forked/spark/python/pyspark/sql/dataframe.py",
line 1734, in toPandas
pdf[f] = pdf[f].astype(t, copy=False)
TypeError: astype() got an unexpected keyword argument 'copy'
```
However, I guess it is really fine becuase:
- 0.10.0 was released in 2012, when Spark was 0.6.x and Java was 6 & 7.
I guess this is really fine. It was 5 years ago.
- It does works without `copy` but the types are not properly set as
proposed here:
```
spark.createDataFrame(data, schema).toPandas().dtypes
a int64 # <- this should be 'int32'
b object
c bool
d float64 # <- this should be 'float32'
```
I am writing this comment only because, up to my knolwedge, we didn't
specify Pandas version requirement -
https://github.com/apache/spark/blob/314cf51ded52834cfbaacf58d3d05a220965ca2a/python/setup.py#L202.
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