[SPARK-8146] DataFrame Python API: Alias replace in df.na

Author: Reynold Xin <rxin@databricks.com>

Closes #6688 from rxin/df-alias-replace and squashes the following commits:

774c19c [Reynold Xin] [SPARK-8146] DataFrame Python API: Alias replace in DataFrameNaFunctions.

python/pyspark/sql/dataframe.py

@@ -909,8 +909,7 @@ class DataFrame(object):
     @since("1.3.1")
     def dropna(self, how='any', thresh=None, subset=None):
         """Returns a new :class:`DataFrame` omitting rows with null values.
-
-        This is an alias for ``na.drop()``.
+        :func:`DataFrame.dropna` and :func:`DataFrameNaFunctions.drop` are aliases of each other.
 
         :param how: 'any' or 'all'.
             If 'any', drop a row if it contains any nulls.
@@ -920,13 +919,6 @@ class DataFrame(object):
             This overwrites the `how` parameter.
         :param subset: optional list of column names to consider.
 
-        >>> df4.dropna().show()
-        +---+------+-----+
-        |age|height| name|
-        +---+------+-----+
-        | 10|    80|Alice|
-        +---+------+-----+
-
         >>> df4.na.drop().show()
         +---+------+-----+
         |age|height| name|
@@ -952,6 +944,7 @@ class DataFrame(object):
     @since("1.3.1")
     def fillna(self, value, subset=None):
         """Replace null values, alias for ``na.fill()``.
+        :func:`DataFrame.fillna` and :func:`DataFrameNaFunctions.fill` are aliases of each other.
 
         :param value: int, long, float, string, or dict.
             Value to replace null values with.
@@ -963,7 +956,7 @@ class DataFrame(object):
             For example, if `value` is a string, and subset contains a non-string column,
             then the non-string column is simply ignored.
 
-        >>> df4.fillna(50).show()
+        >>> df4.na.fill(50).show()
         +---+------+-----+
         |age|height| name|
         +---+------+-----+
@@ -973,16 +966,6 @@ class DataFrame(object):
         | 50|    50| null|
         +---+------+-----+
 
-        >>> df4.fillna({'age': 50, 'name': 'unknown'}).show()
-        +---+------+-------+
-        |age|height|   name|
-        +---+------+-------+
-        | 10|    80|  Alice|
-        |  5|  null|    Bob|
-        | 50|  null|    Tom|
-        | 50|  null|unknown|
-        +---+------+-------+
-
         >>> df4.na.fill({'age': 50, 'name': 'unknown'}).show()
         +---+------+-------+
         |age|height|   name|
@@ -1014,6 +997,8 @@ class DataFrame(object):
     @since(1.4)
     def replace(self, to_replace, value, subset=None):
         """Returns a new :class:`DataFrame` replacing a value with another value.
+        :func:`DataFrame.replace` and :func:`DataFrameNaFunctions.replace` are
+        aliases of each other.
 
         :param to_replace: int, long, float, string, or list.
             Value to be replaced.
@@ -1029,7 +1014,7 @@ class DataFrame(object):
             For example, if `value` is a string, and subset contains a non-string column,
             then the non-string column is simply ignored.
 
-        >>> df4.replace(10, 20).show()
+        >>> df4.na.replace(10, 20).show()
         +----+------+-----+
         | age|height| name|
         +----+------+-----+
@@ -1039,7 +1024,7 @@ class DataFrame(object):
         |null|  null| null|
         +----+------+-----+
 
-        >>> df4.replace(['Alice', 'Bob'], ['A', 'B'], 'name').show()
+        >>> df4.na.replace(['Alice', 'Bob'], ['A', 'B'], 'name').show()
         +----+------+----+
         | age|height|name|
         +----+------+----+
@@ -1090,9 +1075,9 @@ class DataFrame(object):
     @since(1.4)
     def corr(self, col1, col2, method=None):
         """
-        Calculates the correlation of two columns of a DataFrame as a double value. Currently only
-        supports the Pearson Correlation Coefficient.
-        :func:`DataFrame.corr` and :func:`DataFrameStatFunctions.corr` are aliases.
+        Calculates the correlation of two columns of a DataFrame as a double value.
+        Currently only supports the Pearson Correlation Coefficient.
+        :func:`DataFrame.corr` and :func:`DataFrameStatFunctions.corr` are aliases of each other.
 
         :param col1: The name of the first column
         :param col2: The name of the second column
@@ -1241,7 +1226,10 @@ class DataFrame(object):
         import pandas as pd
         return pd.DataFrame.from_records(self.collect(), columns=self.columns)
 
+    ##########################################################################################
     # Pandas compatibility
+    ##########################################################################################
+
     groupby = groupBy
     drop_duplicates = dropDuplicates
 
@@ -1261,6 +1249,8 @@ def _to_scala_map(sc, jm):
 
 class DataFrameNaFunctions(object):
     """Functionality for working with missing data in :class:`DataFrame`.
+
+    .. versionadded:: 1.4
     """
 
     def __init__(self, df):
@@ -1276,9 +1266,16 @@ class DataFrameNaFunctions(object):
 
     fill.__doc__ = DataFrame.fillna.__doc__
 
+    def replace(self, to_replace, value, subset=None):
+        return self.df.replace(to_replace, value, subset)
+
+    replace.__doc__ = DataFrame.replace.__doc__
+
 
 class DataFrameStatFunctions(object):
     """Functionality for statistic functions with :class:`DataFrame`.
+
+    .. versionadded:: 1.4
     """
 
     def __init__(self, df):

python/pyspark/sql/window.py

@@ -32,7 +32,6 @@ def _to_java_cols(cols):
 
 
 class Window(object):
-
     """
     Utility functions for defining window in DataFrames.