Collection function: returns the length of the array or map stored in the column.

    :param col: name of column or expression

    >>> df = spark.createDataFrame([([1, 2, 3],),([1],),([],)], ['data'])
    >>> df.select(size(df.data)).collect()
    [Row(size(data)=3), Row(size(data)=1), Row(size(data)=0)]

def size(col):
    """
    Collection function: returns the length of the array or map stored in the column.

    :param col: name of column or expression

    >>> df = spark.createDataFrame([([1, 2, 3],),([1],),([],)], ['data'])
    >>> df.select(size(df.data)).collect()
    [Row(size(data)=3), Row(size(data)=1), Row(size(data)=0)]
    """
    sc = SparkContext._active_spark_context
    return Column(sc._jvm.functions.size(_to_java_column(col)))