path: root/python/pyspark/sql/dataframe.py

#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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import sys
import warnings
import random

if sys.version >= '3':
    basestring = unicode = str
    long = int
    from functools import reduce
else:
    from itertools import imap as map

from pyspark.rdd import RDD, _load_from_socket, ignore_unicode_prefix
from pyspark.serializers import BatchedSerializer, PickleSerializer, UTF8Deserializer
from pyspark.storagelevel import StorageLevel
from pyspark.traceback_utils import SCCallSiteSync
from pyspark.sql import since
from pyspark.sql.types import _parse_datatype_json_string
from pyspark.sql.column import Column, _to_seq, _to_java_column
from pyspark.sql.readwriter import DataFrameWriter
from pyspark.sql.types import *

__all__ = ["DataFrame", "SchemaRDD", "DataFrameNaFunctions", "DataFrameStatFunctions"]


class DataFrame(object):
    """A distributed collection of data grouped into named columns.

    A :class:`DataFrame` is equivalent to a relational table in Spark SQL,
    and can be created using various functions in :class:`SQLContext`::

        people = sqlContext.read.parquet("...")

    Once created, it can be manipulated using the various domain-specific-language
    (DSL) functions defined in: :class:`DataFrame`, :class:`Column`.

    To select a column from the data frame, use the apply method::

        ageCol = people.age

    A more concrete example::

        # To create DataFrame using SQLContext
        people = sqlContext.read.parquet("...")
        department = sqlContext.read.parquet("...")

        people.filter(people.age > 30).join(department, people.deptId == department.id)) \
          .groupBy(department.name, "gender").agg({"salary": "avg", "age": "max"})

    .. note:: Experimental

    .. versionadded:: 1.3
    """

    def __init__(self, jdf, sql_ctx):
        self._jdf = jdf
        self.sql_ctx = sql_ctx
        self._sc = sql_ctx and sql_ctx._sc
        self.is_cached = False
        self._schema = None  # initialized lazily
        self._lazy_rdd = None

    @property
    @since(1.3)
    def rdd(self):
        """Returns the content as an :class:`pyspark.RDD` of :class:`Row`.
        """
        if self._lazy_rdd is None:
            jrdd = self._jdf.javaToPython()
            self._lazy_rdd = RDD(jrdd, self.sql_ctx._sc, BatchedSerializer(PickleSerializer()))
        return self._lazy_rdd

    @property
    @since("1.3.1")
    def na(self):
        """Returns a :class:`DataFrameNaFunctions` for handling missing values.
        """
        return DataFrameNaFunctions(self)

    @property
    @since(1.4)
    def stat(self):
        """Returns a :class:`DataFrameStatFunctions` for statistic functions.
        """
        return DataFrameStatFunctions(self)

    @ignore_unicode_prefix
    @since(1.3)
    def toJSON(self, use_unicode=True):
        """Converts a :class:`DataFrame` into a :class:`RDD` of string.

        Each row is turned into a JSON document as one element in the returned RDD.

        >>> df.toJSON().first()
        u'{"age":2,"name":"Alice"}'
        """
        rdd = self._jdf.toJSON()
        return RDD(rdd.toJavaRDD(), self._sc, UTF8Deserializer(use_unicode))

    def saveAsParquetFile(self, path):
        """Saves the contents as a Parquet file, preserving the schema.

        .. note:: Deprecated in 1.4, use :func:`DataFrameWriter.parquet` instead.
        """
        warnings.warn("saveAsParquetFile is deprecated. Use write.parquet() instead.")
        self._jdf.saveAsParquetFile(path)

    @since(1.3)
    def registerTempTable(self, name):
        """Registers this RDD as a temporary table using the given name.

        The lifetime of this temporary table is tied to the :class:`SQLContext`
        that was used to create this :class:`DataFrame`.

        >>> df.registerTempTable("people")
        >>> df2 = sqlContext.sql("select * from people")
        >>> sorted(df.collect()) == sorted(df2.collect())
        True
        """
        self._jdf.registerTempTable(name)

    def registerAsTable(self, name):
        """
        .. note:: Deprecated in 1.4, use :func:`registerTempTable` instead.
        """
        warnings.warn("Use registerTempTable instead of registerAsTable.")
        self.registerTempTable(name)

    def insertInto(self, tableName, overwrite=False):
        """Inserts the contents of this :class:`DataFrame` into the specified table.

        .. note:: Deprecated in 1.4, use :func:`DataFrameWriter.insertInto` instead.
        """
        warnings.warn("insertInto is deprecated. Use write.insertInto() instead.")
        self.write.insertInto(tableName, overwrite)

    def saveAsTable(self, tableName, source=None, mode="error", **options):
        """Saves the contents of this :class:`DataFrame` to a data source as a table.

        .. note:: Deprecated in 1.4, use :func:`DataFrameWriter.saveAsTable` instead.
        """
        warnings.warn("insertInto is deprecated. Use write.saveAsTable() instead.")
        self.write.saveAsTable(tableName, source, mode, **options)

    @since(1.3)
    def save(self, path=None, source=None, mode="error", **options):
        """Saves the contents of the :class:`DataFrame` to a data source.

        .. note:: Deprecated in 1.4, use :func:`DataFrameWriter.save` instead.
        """
        warnings.warn("insertInto is deprecated. Use write.save() instead.")
        return self.write.save(path, source, mode, **options)

    @property
    @since(1.4)
    def write(self):
        """
        Interface for saving the content of the :class:`DataFrame` out into external storage.

        :return: :class:`DataFrameWriter`
        """
        return DataFrameWriter(self)

    @property
    @since(1.3)
    def schema(self):
        """Returns the schema of this :class:`DataFrame` as a :class:`types.StructType`.

        >>> df.schema
        StructType(List(StructField(age,IntegerType,true),StructField(name,StringType,true)))
        """
        if self._schema is None:
            try:
                self._schema = _parse_datatype_json_string(self._jdf.schema().json())
            except AttributeError as e:
                raise Exception(
                    "Unable to parse datatype from schema. %s" % e)
        return self._schema

    @since(1.3)
    def printSchema(self):
        """Prints out the schema in the tree format.

        >>> df.printSchema()
        root
         |-- age: integer (nullable = true)
         |-- name: string (nullable = true)
        <BLANKLINE>
        """
        print(self._jdf.schema().treeString())

    @since(1.3)
    def explain(self, extended=False):
        """Prints the (logical and physical) plans to the console for debugging purpose.

        :param extended: boolean, default ``False``. If ``False``, prints only the physical plan.

        >>> df.explain()
        Scan PhysicalRDD[age#0,name#1]

        >>> df.explain(True)
        == Parsed Logical Plan ==
        ...
        == Analyzed Logical Plan ==
        ...
        == Optimized Logical Plan ==
        ...
        == Physical Plan ==
        ...
        """
        if extended:
            print(self._jdf.queryExecution().toString())
        else:
            print(self._jdf.queryExecution().executedPlan().toString())

    @since(1.3)
    def isLocal(self):
        """Returns ``True`` if the :func:`collect` and :func:`take` methods can be run locally
        (without any Spark executors).
        """
        return self._jdf.isLocal()

    @since(1.3)
    def show(self, n=20, truncate=True):
        """Prints the first ``n`` rows to the console.

        :param n: Number of rows to show.
        :param truncate: Whether truncate long strings and align cells right.

        >>> df
        DataFrame[age: int, name: string]
        >>> df.show()
        +---+-----+
        |age| name|
        +---+-----+
        |  2|Alice|
        |  5|  Bob|
        +---+-----+
        """
        print(self._jdf.showString(n, truncate))

    def __repr__(self):
        return "DataFrame[%s]" % (", ".join("%s: %s" % c for c in self.dtypes))

    @since(1.3)
    def count(self):
        """Returns the number of rows in this :class:`DataFrame`.

        >>> df.count()
        2
        """
        return int(self._jdf.count())

    @ignore_unicode_prefix
    @since(1.3)
    def collect(self):
        """Returns all the records as a list of :class:`Row`.

        >>> df.collect()
        [Row(age=2, name=u'Alice'), Row(age=5, name=u'Bob')]
        """
        with SCCallSiteSync(self._sc) as css:
            port = self._sc._jvm.PythonRDD.collectAndServe(self._jdf.javaToPython().rdd())
        return list(_load_from_socket(port, BatchedSerializer(PickleSerializer())))

    @ignore_unicode_prefix
    @since(1.3)
    def limit(self, num):
        """Limits the result count to the number specified.

        >>> df.limit(1).collect()
        [Row(age=2, name=u'Alice')]
        >>> df.limit(0).collect()
        []
        """
        jdf = self._jdf.limit(num)
        return DataFrame(jdf, self.sql_ctx)

    @ignore_unicode_prefix
    @since(1.3)
    def take(self, num):
        """Returns the first ``num`` rows as a :class:`list` of :class:`Row`.

        >>> df.take(2)
        [Row(age=2, name=u'Alice'), Row(age=5, name=u'Bob')]
        """
        return self.limit(num).collect()

    @ignore_unicode_prefix
    @since(1.3)
    def map(self, f):
        """ Returns a new :class:`RDD` by applying a the ``f`` function to each :class:`Row`.

        This is a shorthand for ``df.rdd.map()``.

        >>> df.map(lambda p: p.name).collect()
        [u'Alice', u'Bob']
        """
        return self.rdd.map(f)

    @ignore_unicode_prefix
    @since(1.3)
    def flatMap(self, f):
        """ Returns a new :class:`RDD` by first applying the ``f`` function to each :class:`Row`,
        and then flattening the results.

        This is a shorthand for ``df.rdd.flatMap()``.

        >>> df.flatMap(lambda p: p.name).collect()
        [u'A', u'l', u'i', u'c', u'e', u'B', u'o', u'b']
        """
        return self.rdd.flatMap(f)

    @since(1.3)
    def mapPartitions(self, f, preservesPartitioning=False):
        """Returns a new :class:`RDD` by applying the ``f`` function to each partition.

        This is a shorthand for ``df.rdd.mapPartitions()``.

        >>> rdd = sc.parallelize([1, 2, 3, 4], 4)
        >>> def f(iterator): yield 1
        >>> rdd.mapPartitions(f).sum()
        4
        """
        return self.rdd.mapPartitions(f, preservesPartitioning)

    @since(1.3)
    def foreach(self, f):
        """Applies the ``f`` function to all :class:`Row` of this :class:`DataFrame`.

        This is a shorthand for ``df.rdd.foreach()``.

        >>> def f(person):
        ...     print(person.name)
        >>> df.foreach(f)
        """
        return self.rdd.foreach(f)

    @since(1.3)
    def foreachPartition(self, f):
        """Applies the ``f`` function to each partition of this :class:`DataFrame`.

        This a shorthand for ``df.rdd.foreachPartition()``.

        >>> def f(people):
        ...     for person in people:
        ...         print(person.name)
        >>> df.foreachPartition(f)
        """
        return self.rdd.foreachPartition(f)

    @since(1.3)
    def cache(self):
        """ Persists with the default storage level (C{MEMORY_ONLY_SER}).
        """
        self.is_cached = True
        self._jdf.cache()
        return self

    @since(1.3)
    def persist(self, storageLevel=StorageLevel.MEMORY_ONLY_SER):
        """Sets the storage level to persist its values across operations
        after the first time it is computed. This can only be used to assign
        a new storage level if the RDD does not have a storage level set yet.
        If no storage level is specified defaults to (C{MEMORY_ONLY_SER}).
        """
        self.is_cached = True
        javaStorageLevel = self._sc._getJavaStorageLevel(storageLevel)
        self._jdf.persist(javaStorageLevel)
        return self

    @since(1.3)
    def unpersist(self, blocking=True):
        """Marks the :class:`DataFrame` as non-persistent, and remove all blocks for it from
        memory and disk.
        """
        self.is_cached = False
        self._jdf.unpersist(blocking)
        return self

    @since(1.4)
    def coalesce(self, numPartitions):
        """
        Returns a new :class:`DataFrame` that has exactly `numPartitions` partitions.

        Similar to coalesce defined on an :class:`RDD`, this operation results in a
        narrow dependency, e.g. if you go from 1000 partitions to 100 partitions,
        there will not be a shuffle, instead each of the 100 new partitions will
        claim 10 of the current partitions.

        >>> df.coalesce(1).rdd.getNumPartitions()
        1
        """
        return DataFrame(self._jdf.coalesce(numPartitions), self.sql_ctx)

    @since(1.3)
    def repartition(self, numPartitions):
        """Returns a new :class:`DataFrame` that has exactly ``numPartitions`` partitions.

        >>> df.repartition(10).rdd.getNumPartitions()
        10
        """
        return DataFrame(self._jdf.repartition(numPartitions), self.sql_ctx)

    @since(1.3)
    def distinct(self):
        """Returns a new :class:`DataFrame` containing the distinct rows in this :class:`DataFrame`.

        >>> df.distinct().count()
        2
        """
        return DataFrame(self._jdf.distinct(), self.sql_ctx)

    @since(1.3)
    def sample(self, withReplacement, fraction, seed=None):
        """Returns a sampled subset of this :class:`DataFrame`.

        >>> df.sample(False, 0.5, 42).count()
        1
        """
        assert fraction >= 0.0, "Negative fraction value: %s" % fraction
        seed = seed if seed is not None else random.randint(0, sys.maxsize)
        rdd = self._jdf.sample(withReplacement, fraction, long(seed))
        return DataFrame(rdd, self.sql_ctx)

    @since(1.5)
    def sampleBy(self, col, fractions, seed=None):
        """
        Returns a stratified sample without replacement based on the
        fraction given on each stratum.

        :param col: column that defines strata
        :param fractions:
            sampling fraction for each stratum. If a stratum is not
            specified, we treat its fraction as zero.
        :param seed: random seed
        :return: a new DataFrame that represents the stratified sample

        >>> from pyspark.sql.functions import col
        >>> dataset = sqlContext.range(0, 100).select((col("id") % 3).alias("key"))
        >>> sampled = dataset.sampleBy("key", fractions={0: 0.1, 1: 0.2}, seed=0)
        >>> sampled.groupBy("key").count().orderBy("key").show()
        +---+-----+
        |key|count|
        +---+-----+
        |  0|    3|
        |  1|    8|
        +---+-----+

        """
        if not isinstance(col, str):
            raise ValueError("col must be a string, but got %r" % type(col))
        if not isinstance(fractions, dict):
            raise ValueError("fractions must be a dict but got %r" % type(fractions))
        for k, v in fractions.items():
            if not isinstance(k, (float, int, long, basestring)):
                raise ValueError("key must be float, int, long, or string, but got %r" % type(k))
            fractions[k] = float(v)
        seed = seed if seed is not None else random.randint(0, sys.maxsize)
        return DataFrame(self._jdf.stat().sampleBy(col, self._jmap(fractions), seed), self.sql_ctx)

    @since(1.4)
    def randomSplit(self, weights, seed=None):
        """Randomly splits this :class:`DataFrame` with the provided weights.

        :param weights: list of doubles as weights with which to split the DataFrame. Weights will
            be normalized if they don't sum up to 1.0.
        :param seed: The seed for sampling.

        >>> splits = df4.randomSplit([1.0, 2.0], 24)
        >>> splits[0].count()
        1

        >>> splits[1].count()
        3
        """
        for w in weights:
            if w < 0.0:
                raise ValueError("Weights must be positive. Found weight value: %s" % w)
        seed = seed if seed is not None else random.randint(0, sys.maxsize)
        rdd_array = self._jdf.randomSplit(_to_seq(self.sql_ctx._sc, weights), long(seed))
        return [DataFrame(rdd, self.sql_ctx) for rdd in rdd_array]

    @property
    @since(1.3)
    def dtypes(self):
        """Returns all column names and their data types as a list.

        >>> df.dtypes
        [('age', 'int'), ('name', 'string')]
        """
        return [(str(f.name), f.dataType.simpleString()) for f in self.schema.fields]

    @property
    @since(1.3)
    def columns(self):
        """Returns all column names as a list.

        >>> df.columns
        ['age', 'name']
        """
        return [f.name for f in self.schema.fields]

    @ignore_unicode_prefix
    @since(1.3)
    def alias(self, alias):
        """Returns a new :class:`DataFrame` with an alias set.

        >>> from pyspark.sql.functions import *
        >>> df_as1 = df.alias("df_as1")
        >>> df_as2 = df.alias("df_as2")
        >>> joined_df = df_as1.join(df_as2, col("df_as1.name") == col("df_as2.name"), 'inner')
        >>> joined_df.select(col("df_as1.name"), col("df_as2.name"), col("df_as2.age")).collect()
        [Row(name=u'Alice', name=u'Alice', age=2), Row(name=u'Bob', name=u'Bob', age=5)]
        """
        assert isinstance(alias, basestring), "alias should be a string"
        return DataFrame(getattr(self._jdf, "as")(alias), self.sql_ctx)

    @ignore_unicode_prefix
    @since(1.3)
    def join(self, other, on=None, how=None):
        """Joins with another :class:`DataFrame`, using the given join expression.

        The following performs a full outer join between ``df1`` and ``df2``.

        :param other: Right side of the join
        :param on: a string for join column name, a list of column names,
            , a join expression (Column) or a list of Columns.
            If `on` is a string or a list of string indicating the name of the join column(s),
            the column(s) must exist on both sides, and this performs an inner equi-join.
        :param how: str, default 'inner'.
            One of `inner`, `outer`, `left_outer`, `right_outer`, `semijoin`.

        >>> df.join(df2, df.name == df2.name, 'outer').select(df.name, df2.height).collect()
        [Row(name=None, height=80), Row(name=u'Alice', height=None), Row(name=u'Bob', height=85)]

        >>> cond = [df.name == df3.name, df.age == df3.age]
        >>> df.join(df3, cond, 'outer').select(df.name, df3.age).collect()
        [Row(name=u'Bob', age=5), Row(name=u'Alice', age=2)]

        >>> df.join(df2, 'name').select(df.name, df2.height).collect()
        [Row(name=u'Bob', height=85)]

        >>> df.join(df4, ['name', 'age']).select(df.name, df.age).collect()
        [Row(name=u'Bob', age=5)]
        """

        if on is not None and not isinstance(on, list):
            on = [on]

        if on is None or len(on) == 0:
            jdf = self._jdf.join(other._jdf)
        elif isinstance(on[0], basestring):
            jdf = self._jdf.join(other._jdf, self._jseq(on))
        else:
            assert isinstance(on[0], Column), "on should be Column or list of Column"
            if len(on) > 1:
                on = reduce(lambda x, y: x.__and__(y), on)
            else:
                on = on[0]
            if how is None:
                jdf = self._jdf.join(other._jdf, on._jc, "inner")
            else:
                assert isinstance(how, basestring), "how should be basestring"
                jdf = self._jdf.join(other._jdf, on._jc, how)
        return DataFrame(jdf, self.sql_ctx)

    @ignore_unicode_prefix
    @since(1.3)
    def sort(self, *cols, **kwargs):
        """Returns a new :class:`DataFrame` sorted by the specified column(s).

        :param cols: list of :class:`Column` or column names to sort by.
        :param ascending: boolean or list of boolean (default True).
            Sort ascending vs. descending. Specify list for multiple sort orders.
            If a list is specified, length of the list must equal length of the `cols`.

        >>> df.sort(df.age.desc()).collect()
        [Row(age=5, name=u'Bob'), Row(age=2, name=u'Alice')]
        >>> df.sort("age", ascending=False).collect()
        [Row(age=5, name=u'Bob'), Row(age=2, name=u'Alice')]
        >>> df.orderBy(df.age.desc()).collect()
        [Row(age=5, name=u'Bob'), Row(age=2, name=u'Alice')]
        >>> from pyspark.sql.functions import *
        >>> df.sort(asc("age")).collect()
        [Row(age=2, name=u'Alice'), Row(age=5, name=u'Bob')]
        >>> df.orderBy(desc("age"), "name").collect()
        [Row(age=5, name=u'Bob'), Row(age=2, name=u'Alice')]
        >>> df.orderBy(["age", "name"], ascending=[0, 1]).collect()
        [Row(age=5, name=u'Bob'), Row(age=2, name=u'Alice')]
        """
        if not cols:
            raise ValueError("should sort by at least one column")
        if len(cols) == 1 and isinstance(cols[0], list):
            cols = cols[0]
        jcols = [_to_java_column(c) for c in cols]
        ascending = kwargs.get('ascending', True)
        if isinstance(ascending, (bool, int)):
            if not ascending:
                jcols = [jc.desc() for jc in jcols]
        elif isinstance(ascending, list):
            jcols = [jc if asc else jc.desc()
                     for asc, jc in zip(ascending, jcols)]
        else:
            raise TypeError("ascending can only be boolean or list, but got %s" % type(ascending))

        jdf = self._jdf.sort(self._jseq(jcols))
        return DataFrame(jdf, self.sql_ctx)

    orderBy = sort

    def _jseq(self, cols, converter=None):
        """Return a JVM Seq of Columns from a list of Column or names"""
        return _to_seq(self.sql_ctx._sc, cols, converter)

    def _jmap(self, jm):
        """Return a JVM Scala Map from a dict"""
        return _to_scala_map(self.sql_ctx._sc, jm)

    def _jcols(self, *cols):
        """Return a JVM Seq of Columns from a list of Column or column names

        If `cols` has only one list in it, cols[0] will be used as the list.
        """
        if len(cols) == 1 and isinstance(cols[0], list):
            cols = cols[0]
        return self._jseq(cols, _to_java_column)

    @since("1.3.1")
    def describe(self, *cols):
        """Computes statistics for numeric columns.

        This include count, mean, stddev, min, and max. If no columns are
        given, this function computes statistics for all numerical columns.

        .. note:: This function is meant for exploratory data analysis, as we make no \
        guarantee about the backward compatibility of the schema of the resulting DataFrame.

        >>> df.describe().show()
        +-------+---+
        |summary|age|
        +-------+---+
        |  count|  2|
        |   mean|3.5|
        | stddev|1.5|
        |    min|  2|
        |    max|  5|
        +-------+---+
        >>> df.describe(['age', 'name']).show()
        +-------+---+-----+
        |summary|age| name|
        +-------+---+-----+
        |  count|  2|    2|
        |   mean|3.5| null|
        | stddev|1.5| null|
        |    min|  2|Alice|
        |    max|  5|  Bob|
        +-------+---+-----+
        """
        if len(cols) == 1 and isinstance(cols[0], list):
            cols = cols[0]
        jdf = self._jdf.describe(self._jseq(cols))
        return DataFrame(jdf, self.sql_ctx)

    @ignore_unicode_prefix
    @since(1.3)
    def head(self, n=None):
        """Returns the first ``n`` rows.

        :param n: int, default 1. Number of rows to return.
        :return: If n is greater than 1, return a list of :class:`Row`.
            If n is 1, return a single Row.

        >>> df.head()
        Row(age=2, name=u'Alice')
        >>> df.head(1)
        [Row(age=2, name=u'Alice')]
        """
        if n is None:
            rs = self.head(1)
            return rs[0] if rs else None
        return self.take(n)

    @ignore_unicode_prefix
    @since(1.3)
    def first(self):
        """Returns the first row as a :class:`Row`.

        >>> df.first()
        Row(age=2, name=u'Alice')
        """
        return self.head()

    @ignore_unicode_prefix
    @since(1.3)
    def __getitem__(self, item):
        """Returns the column as a :class:`Column`.

        >>> df.select(df['age']).collect()
        [Row(age=2), Row(age=5)]
        >>> df[ ["name", "age"]].collect()
        [Row(name=u'Alice', age=2), Row(name=u'Bob', age=5)]
        >>> df[ df.age > 3 ].collect()
        [Row(age=5, name=u'Bob')]
        >>> df[df[0] > 3].collect()
        [Row(age=5, name=u'Bob')]
        """
        if isinstance(item, basestring):
            jc = self._jdf.apply(item)
            return Column(jc)
        elif isinstance(item, Column):
            return self.filter(item)
        elif isinstance(item, (list, tuple)):
            return self.select(*item)
        elif isinstance(item, int):
            jc = self._jdf.apply(self.columns[item])
            return Column(jc)
        else:
            raise TypeError("unexpected item type: %s" % type(item))

    @since(1.3)
    def __getattr__(self, name):
        """Returns the :class:`Column` denoted by ``name``.

        >>> df.select(df.age).collect()
        [Row(age=2), Row(age=5)]
        """
        if name not in self.columns:
            raise AttributeError(
                "'%s' object has no attribute '%s'" % (self.__class__.__name__, name))
        jc = self._jdf.apply(name)
        return Column(jc)

    @ignore_unicode_prefix
    @since(1.3)
    def select(self, *cols):
        """Projects a set of expressions and returns a new :class:`DataFrame`.

        :param cols: list of column names (string) or expressions (:class:`Column`).
            If one of the column names is '*', that column is expanded to include all columns
            in the current DataFrame.

        >>> df.select('*').collect()
        [Row(age=2, name=u'Alice'), Row(age=5, name=u'Bob')]
        >>> df.select('name', 'age').collect()
        [Row(name=u'Alice', age=2), Row(name=u'Bob', age=5)]
        >>> df.select(df.name, (df.age + 10).alias('age')).collect()
        [Row(name=u'Alice', age=12), Row(name=u'Bob', age=15)]
        """
        jdf = self._jdf.select(self._jcols(*cols))
        return DataFrame(jdf, self.sql_ctx)

    @since(1.3)
    def selectExpr(self, *expr):
        """Projects a set of SQL expressions and returns a new :class:`DataFrame`.

        This is a variant of :func:`select` that accepts SQL expressions.

        >>> df.selectExpr("age * 2", "abs(age)").collect()
        [Row((age * 2)=4, 'abs(age)=2), Row((age * 2)=10, 'abs(age)=5)]
        """
        if len(expr) == 1 and isinstance(expr[0], list):
            expr = expr[0]
        jdf = self._jdf.selectExpr(self._jseq(expr))
        return DataFrame(jdf, self.sql_ctx)

    @ignore_unicode_prefix
    @since(1.3)
    def filter(self, condition):
        """Filters rows using the given condition.

        :func:`where` is an alias for :func:`filter`.

        :param condition: a :class:`Column` of :class:`types.BooleanType`
            or a string of SQL expression.

        >>> df.filter(df.age > 3).collect()
        [Row(age=5, name=u'Bob')]
        >>> df.where(df.age == 2).collect()
        [Row(age=2, name=u'Alice')]

        >>> df.filter("age > 3").collect()
        [Row(age=5, name=u'Bob')]
        >>> df.where("age = 2").collect()
        [Row(age=2, name=u'Alice')]
        """
        if isinstance(condition, basestring):
            jdf = self._jdf.filter(condition)
        elif isinstance(condition, Column):
            jdf = self._jdf.filter(condition._jc)
        else:
            raise TypeError("condition should be string or Column")
        return DataFrame(jdf, self.sql_ctx)

    where = filter

    @ignore_unicode_prefix
    @since(1.3)
    def groupBy(self, *cols):
        """Groups the :class:`DataFrame` using the specified columns,
        so we can run aggregation on them. See :class:`GroupedData`
        for all the available aggregate functions.

        :func:`groupby` is an alias for :func:`groupBy`.

        :param cols: list of columns to group by.
            Each element should be a column name (string) or an expression (:class:`Column`).

        >>> df.groupBy().avg().collect()
        [Row(avg(age)=3.5)]
        >>> df.groupBy('name').agg({'age': 'mean'}).collect()
        [Row(name=u'Alice', avg(age)=2.0), Row(name=u'Bob', avg(age)=5.0)]
        >>> df.groupBy(df.name).avg().collect()
        [Row(name=u'Alice', avg(age)=2.0), Row(name=u'Bob', avg(age)=5.0)]
        >>> df.groupBy(['name', df.age]).count().collect()
        [Row(name=u'Bob', age=5, count=1), Row(name=u'Alice', age=2, count=1)]
        """
        jgd = self._jdf.groupBy(self._jcols(*cols))
        from pyspark.sql.group import GroupedData
        return GroupedData(jgd, self.sql_ctx)

    @since(1.4)
    def rollup(self, *cols):
        """
        Create a multi-dimensional rollup for the current :class:`DataFrame` using
        the specified columns, so we can run aggregation on them.

        >>> df.rollup('name', df.age).count().show()
        +-----+----+-----+
        | name| age|count|
        +-----+----+-----+
        |Alice|null|    1|
        |  Bob|   5|    1|
        |  Bob|null|    1|
        | null|null|    2|
        |Alice|   2|    1|
        +-----+----+-----+
        """
        jgd = self._jdf.rollup(self._jcols(*cols))
        from pyspark.sql.group import GroupedData
        return GroupedData(jgd, self.sql_ctx)

    @since(1.4)
    def cube(self, *cols):
        """
        Create a multi-dimensional cube for the current :class:`DataFrame` using
        the specified columns, so we can run aggregation on them.

        >>> df.cube('name', df.age).count().show()
        +-----+----+-----+
        | name| age|count|
        +-----+----+-----+
        | null|   2|    1|
        |Alice|null|    1|
        |  Bob|   5|    1|
        |  Bob|null|    1|
        | null|   5|    1|
        | null|null|    2|
        |Alice|   2|    1|
        +-----+----+-----+
        """
        jgd = self._jdf.cube(self._jcols(*cols))
        from pyspark.sql.group import GroupedData
        return GroupedData(jgd, self.sql_ctx)

    @since(1.3)
    def agg(self, *exprs):
        """ Aggregate on the entire :class:`DataFrame` without groups
        (shorthand for ``df.groupBy.agg()``).

        >>> df.agg({"age": "max"}).collect()
        [Row(max(age)=5)]
        >>> from pyspark.sql import functions as F
        >>> df.agg(F.min(df.age)).collect()
        [Row(min(age)=2)]
        """
        return self.groupBy().agg(*exprs)

    @since(1.3)
    def unionAll(self, other):
        """ Return a new :class:`DataFrame` containing union of rows in this
        frame and another frame.

        This is equivalent to `UNION ALL` in SQL.
        """
        return DataFrame(self._jdf.unionAll(other._jdf), self.sql_ctx)

    @since(1.3)
    def intersect(self, other):
        """ Return a new :class:`DataFrame` containing rows only in
        both this frame and another frame.

        This is equivalent to `INTERSECT` in SQL.
        """
        return DataFrame(self._jdf.intersect(other._jdf), self.sql_ctx)

    @since(1.3)
    def subtract(self, other):
        """ Return a new :class:`DataFrame` containing rows in this frame
        but not in another frame.

        This is equivalent to `EXCEPT` in SQL.
        """
        return DataFrame(getattr(self._jdf, "except")(other._jdf), self.sql_ctx)

    @since(1.4)
    def dropDuplicates(self, subset=None):
        """Return a new :class:`DataFrame` with duplicate rows removed,
        optionally only considering certain columns.

        >>> from pyspark.sql import Row
        >>> df = sc.parallelize([ \
            Row(name='Alice', age=5, height=80), \
            Row(name='Alice', age=5, height=80), \
            Row(name='Alice', age=10, height=80)]).toDF()
        >>> df.dropDuplicates().show()
        +---+------+-----+
        |age|height| name|
        +---+------+-----+
        |  5|    80|Alice|
        | 10|    80|Alice|
        +---+------+-----+

        >>> df.dropDuplicates(['name', 'height']).show()
        +---+------+-----+
        |age|height| name|
        +---+------+-----+
        |  5|    80|Alice|
        +---+------+-----+
        """
        if subset is None:
            jdf = self._jdf.dropDuplicates()
        else:
            jdf = self._jdf.dropDuplicates(self._jseq(subset))
        return DataFrame(jdf, self.sql_ctx)

    @since("1.3.1")
    def dropna(self, how='any', thresh=None, subset=None):
        """Returns a new :class:`DataFrame` omitting rows with null values.
        :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.
            If 'all', drop a row only if all its values are null.
        :param thresh: int, default None
            If specified, drop rows that have less than `thresh` non-null values.
            This overwrites the `how` parameter.
        :param subset: optional list of column names to consider.

        >>> df4.na.drop().show()
        +---+------+-----+
        |age|height| name|
        +---+------+-----+
        | 10|    80|Alice|
        +---+------+-----+
        """
        if how is not None and how not in ['any', 'all']:
            raise ValueError("how ('" + how + "') should be 'any' or 'all'")

        if subset is None:
            subset = self.columns
        elif isinstance(subset, basestring):
            subset = [subset]
        elif not isinstance(subset, (list, tuple)):
            raise ValueError("subset should be a list or tuple of column names")

        if thresh is None:
            thresh = len(subset) if how == 'any' else 1

        return DataFrame(self._jdf.na().drop(thresh, self._jseq(subset)), self.sql_ctx)

    @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.
            If the value is a dict, then `subset` is ignored and `value` must be a mapping
            from column name (string) to replacement value. The replacement value must be
            an int, long, float, or string.
        :param subset: optional list of column names to consider.
            Columns specified in subset that do not have matching data type are ignored.
            For example, if `value` is a string, and subset contains a non-string column,
            then the non-string column is simply ignored.

        >>> df4.na.fill(50).show()
        +---+------+-----+
        |age|height| name|
        +---+------+-----+
        | 10|    80|Alice|
        |  5|    50|  Bob|
        | 50|    50|  Tom|
        | 50|    50| null|
        +---+------+-----+

        >>> df4.na.fill({'age': 50, 'name': 'unknown'}).show()
        +---+------+-------+
        |age|height|   name|
        +---+------+-------+
        | 10|    80|  Alice|
        |  5|  null|    Bob|
        | 50|  null|    Tom|
        | 50|  null|unknown|
        +---+------+-------+
        """
        if not isinstance(value, (float, int, long, basestring, dict)):
            raise ValueError("value should be a float, int, long, string, or dict")

        if isinstance(value, (int, long)):
            value = float(value)

        if isinstance(value, dict):
            return DataFrame(self._jdf.na().fill(value), self.sql_ctx)
        elif subset is None:
            return DataFrame(self._jdf.na().fill(value), self.sql_ctx)
        else:
            if isinstance(subset, basestring):
                subset = [subset]
            elif not isinstance(subset, (list, tuple)):
                raise ValueError("subset should be a list or tuple of column names")

            return DataFrame(self._jdf.na().fill(value, self._jseq(subset)), self.sql_ctx)

    @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.
            If the value is a dict, then `value` is ignored and `to_replace` must be a
            mapping from column name (string) to replacement value. The value to be
            replaced must be an int, long, float, or string.
        :param value: int, long, float, string, or list.
            Value to use to replace holes.
            The replacement value must be an int, long, float, or string. If `value` is a
            list or tuple, `value` should be of the same length with `to_replace`.
        :param subset: optional list of column names to consider.
            Columns specified in subset that do not have matching data type are ignored.
            For example, if `value` is a string, and subset contains a non-string column,
            then the non-string column is simply ignored.

        >>> df4.na.replace(10, 20).show()
        +----+------+-----+
        | age|height| name|
        +----+------+-----+
        |  20|    80|Alice|
        |   5|  null|  Bob|
        |null|  null|  Tom|
        |null|  null| null|
        +----+------+-----+

        >>> df4.na.replace(['Alice', 'Bob'], ['A', 'B'], 'name').show()
        +----+------+----+
        | age|height|name|
        +----+------+----+
        |  10|    80|   A|
        |   5|  null|   B|
        |null|  null| Tom|
        |null|  null|null|
        +----+------+----+
        """
        if not isinstance(to_replace, (float, int, long, basestring, list, tuple, dict)):
            raise ValueError(
                "to_replace should be a float, int, long, string, list, tuple, or dict")

        if not isinstance(value, (float, int, long, basestring, list, tuple)):
            raise ValueError("value should be a float, int, long, string, list, or tuple")

        rep_dict = dict()

        if isinstance(to_replace, (float, int, long, basestring)):
            to_replace = [to_replace]

        if isinstance(to_replace, tuple):
            to_replace = list(to_replace)

        if isinstance(value, tuple):
            value = list(value)

        if isinstance(to_replace, list) and isinstance(value, list):
            if len(to_replace) != len(value):
                raise ValueError("to_replace and value lists should be of the same length")
            rep_dict = dict(zip(to_replace, value))
        elif isinstance(to_replace, list) and isinstance(value, (float, int, long, basestring)):
            rep_dict = dict([(tr, value) for tr in to_replace])
        elif isinstance(to_replace, dict):
            rep_dict = to_replace

        if subset is None:
            return DataFrame(self._jdf.na().replace('*', rep_dict), self.sql_ctx)
        elif isinstance(subset, basestring):
            subset = [subset]

        if not isinstance(subset, (list, tuple)):
            raise ValueError("subset should be a list or tuple of column names")

        return DataFrame(
            self._jdf.na().replace(self._jseq(subset), self._jmap(rep_dict)), self.sql_ctx)

    @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 of each other.

        :param col1: The name of the first column
        :param col2: The name of the second column
        :param method: The correlation method. Currently only supports "pearson"
        """
        if not isinstance(col1, str):
            raise ValueError("col1 should be a string.")
        if not isinstance(col2, str):
            raise ValueError("col2 should be a string.")
        if not method:
            method = "pearson"
        if not method == "pearson":
            raise ValueError("Currently only the calculation of the Pearson Correlation " +
                             "coefficient is supported.")
        return self._jdf.stat().corr(col1, col2, method)

    @since(1.4)
    def cov(self, col1, col2):
        """
        Calculate the sample covariance for the given columns, specified by their names, as a
        double value. :func:`DataFrame.cov` and :func:`DataFrameStatFunctions.cov` are aliases.

        :param col1: The name of the first column
        :param col2: The name of the second column
        """
        if not isinstance(col1, str):
            raise ValueError("col1 should be a string.")
        if not isinstance(col2, str):
            raise ValueError("col2 should be a string.")
        return self._jdf.stat().cov(col1, col2)

    @since(1.4)
    def crosstab(self, col1, col2):
        """
        Computes a pair-wise frequency table of the given columns. Also known as a contingency
        table. The number of distinct values for each column should be less than 1e4. At most 1e6
        non-zero pair frequencies will be returned.
        The first column of each row will be the distinct values of `col1` and the column names
        will be the distinct values of `col2`. The name of the first column will be `$col1_$col2`.
        Pairs that have no occurrences will have zero as their counts.
        :func:`DataFrame.crosstab` and :func:`DataFrameStatFunctions.crosstab` are aliases.

        :param col1: The name of the first column. Distinct items will make the first item of
            each row.
        :param col2: The name of the second column. Distinct items will make the column names
            of the DataFrame.
        """
        if not isinstance(col1, str):
            raise ValueError("col1 should be a string.")
        if not isinstance(col2, str):
            raise ValueError("col2 should be a string.")
        return DataFrame(self._jdf.stat().crosstab(col1, col2), self.sql_ctx)

    @since(1.4)
    def freqItems(self, cols, support=None):
        """
        Finding frequent items for columns, possibly with false positives. Using the
        frequent element count algorithm described in
        "http://dx.doi.org/10.1145/762471.762473, proposed by Karp, Schenker, and Papadimitriou".
        :func:`DataFrame.freqItems` and :func:`DataFrameStatFunctions.freqItems` are aliases.

        .. note::  This function is meant for exploratory data analysis, as we make no \
        guarantee about the backward compatibility of the schema of the resulting DataFrame.

        :param cols: Names of the columns to calculate frequent items for as a list or tuple of
            strings.
        :param support: The frequency with which to consider an item 'frequent'. Default is 1%.
            The support must be greater than 1e-4.
        """
        if isinstance(cols, tuple):
            cols = list(cols)
        if not isinstance(cols, list):
            raise ValueError("cols must be a list or tuple of column names as strings.")
        if not support:
            support = 0.01
        return DataFrame(self._jdf.stat().freqItems(_to_seq(self._sc, cols), support), self.sql_ctx)

    @ignore_unicode_prefix
    @since(1.3)
    def withColumn(self, colName, col):
        """
        Returns a new :class:`DataFrame` by adding a column or replacing the
        existing column that has the same name.

        :param colName: string, name of the new column.
        :param col: a :class:`Column` expression for the new column.

        >>> df.withColumn('age2', df.age + 2).collect()
        [Row(age=2, name=u'Alice', age2=4), Row(age=5, name=u'Bob', age2=7)]
        """
        assert isinstance(col, Column), "col should be Column"
        return DataFrame(self._jdf.withColumn(colName, col._jc), self.sql_ctx)

    @ignore_unicode_prefix
    @since(1.3)
    def withColumnRenamed(self, existing, new):
        """Returns a new :class:`DataFrame` by renaming an existing column.

        :param existing: string, name of the existing column to rename.
        :param col: string, new name of the column.

        >>> df.withColumnRenamed('age', 'age2').collect()
        [Row(age2=2, name=u'Alice'), Row(age2=5, name=u'Bob')]
        """
        return DataFrame(self._jdf.withColumnRenamed(existing, new), self.sql_ctx)

    @since(1.4)
    @ignore_unicode_prefix
    def drop(self, col):
        """Returns a new :class:`DataFrame` that drops the specified column.

        :param col: a string name of the column to drop, or a
            :class:`Column` to drop.

        >>> df.drop('age').collect()
        [Row(name=u'Alice'), Row(name=u'Bob')]

        >>> df.drop(df.age).collect()
        [Row(name=u'Alice'), Row(name=u'Bob')]

        >>> df.join(df2, df.name == df2.name, 'inner').drop(df.name).collect()
        [Row(age=5, height=85, name=u'Bob')]

        >>> df.join(df2, df.name == df2.name, 'inner').drop(df2.name).collect()
        [Row(age=5, name=u'Bob', height=85)]
        """
        if isinstance(col, basestring):
            jdf = self._jdf.drop(col)
        elif isinstance(col, Column):
            jdf = self._jdf.drop(col._jc)
        else:
            raise TypeError("col should be a string or a Column")
        return DataFrame(jdf, self.sql_ctx)

    @since(1.3)
    def toPandas(self):
        """Returns the contents of this :class:`DataFrame` as Pandas ``pandas.DataFrame``.

        This is only available if Pandas is installed and available.

        >>> df.toPandas()  # doctest: +SKIP
           age   name
        0    2  Alice
        1    5    Bob
        """
        import pandas as pd
        return pd.DataFrame.from_records(self.collect(), columns=self.columns)

    ##########################################################################################
    # Pandas compatibility
    ##########################################################################################

    groupby = groupBy
    drop_duplicates = dropDuplicates


# Having SchemaRDD for backward compatibility (for docs)
class SchemaRDD(DataFrame):
    """SchemaRDD is deprecated, please use :class:`DataFrame`.
    """


def _to_scala_map(sc, jm):
    """
    Convert a dict into a JVM Map.
    """
    return sc._jvm.PythonUtils.toScalaMap(jm)


class DataFrameNaFunctions(object):
    """Functionality for working with missing data in :class:`DataFrame`.

    .. versionadded:: 1.4
    """

    def __init__(self, df):
        self.df = df

    def drop(self, how='any', thresh=None, subset=None):
        return self.df.dropna(how=how, thresh=thresh, subset=subset)

    drop.__doc__ = DataFrame.dropna.__doc__

    def fill(self, value, subset=None):
        return self.df.fillna(value=value, subset=subset)

    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):
        self.df = df

    def corr(self, col1, col2, method=None):
        return self.df.corr(col1, col2, method)

    corr.__doc__ = DataFrame.corr.__doc__

    def cov(self, col1, col2):
        return self.df.cov(col1, col2)

    cov.__doc__ = DataFrame.cov.__doc__

    def crosstab(self, col1, col2):
        return self.df.crosstab(col1, col2)

    crosstab.__doc__ = DataFrame.crosstab.__doc__

    def freqItems(self, cols, support=None):
        return self.df.freqItems(cols, support)

    freqItems.__doc__ = DataFrame.freqItems.__doc__

    def sampleBy(self, col, fractions, seed=None):
        return self.df.sampleBy(col, fractions, seed)

    sampleBy.__doc__ = DataFrame.sampleBy.__doc__


def _test():
    import doctest
    from pyspark.context import SparkContext
    from pyspark.sql import Row, SQLContext
    import pyspark.sql.dataframe
    globs = pyspark.sql.dataframe.__dict__.copy()
    sc = SparkContext('local[4]', 'PythonTest')
    globs['sc'] = sc
    globs['sqlContext'] = SQLContext(sc)
    globs['df'] = sc.parallelize([(2, 'Alice'), (5, 'Bob')])\
        .toDF(StructType([StructField('age', IntegerType()),
                          StructField('name', StringType())]))
    globs['df2'] = sc.parallelize([Row(name='Tom', height=80), Row(name='Bob', height=85)]).toDF()
    globs['df3'] = sc.parallelize([Row(name='Alice', age=2),
                                   Row(name='Bob', age=5)]).toDF()
    globs['df4'] = sc.parallelize([Row(name='Alice', age=10, height=80),
                                  Row(name='Bob', age=5, height=None),
                                  Row(name='Tom', age=None, height=None),
                                  Row(name=None, age=None, height=None)]).toDF()

    (failure_count, test_count) = doctest.testmod(
        pyspark.sql.dataframe, globs=globs,
        optionflags=doctest.ELLIPSIS | doctest.NORMALIZE_WHITESPACE | doctest.REPORT_NDIFF)
    globs['sc'].stop()
    if failure_count:
        exit(-1)


if __name__ == "__main__":
    _test()