我来自熊猫的背景,我习惯了从CSV文件读取数据到一个dataframe,然后简单地改变列名使用简单的命令有用的东西:

df.columns = new_column_name_list

然而,这在使用sqlContext创建的PySpark数据框架中是行不通的。 我能想到的唯一解决办法是:

df = sqlContext.read.format("com.databricks.spark.csv").options(header='false', inferschema='true', delimiter='\t').load("data.txt")
oldSchema = df.schema
for i,k in enumerate(oldSchema.fields):
  k.name = new_column_name_list[i]
df = sqlContext.read.format("com.databricks.spark.csv").options(header='false', delimiter='\t').load("data.txt", schema=oldSchema)

这基本上是定义变量两次,首先推断模式,然后重命名列名,然后用更新的模式再次加载数据框架。

有没有更好更有效的方法来做到这一点,就像我们对熊猫做的那样?

我的Spark版本是1.5.0


当前回答

对于单个列重命名,仍然可以使用toDF()。例如,

df1.selectExpr("SALARY*2").toDF("REVISED_SALARY").show()

其他回答

列表理解+ f-string:

df = df.toDF(*[f'n_{c}' for c in df.columns])

简单的列表理解:

df = df.toDF(*[c.lower() for c in df.columns])

我做了一个易于使用的函数来重命名pyspark dataframe的多个列, 如果有人想使用它:

def renameCols(df, old_columns, new_columns):
    for old_col,new_col in zip(old_columns,new_columns):
        df = df.withColumnRenamed(old_col,new_col)
    return df

old_columns = ['old_name1','old_name2']
new_columns = ['new_name1', 'new_name2']
df_renamed = renameCols(df, old_columns, new_columns)

注意,两个列表的长度必须相同。

有很多方法可以做到这一点:

Option 1. Using selectExpr. data = sqlContext.createDataFrame([("Alberto", 2), ("Dakota", 2)], ["Name", "askdaosdka"]) data.show() data.printSchema() # Output #+-------+----------+ #| Name|askdaosdka| #+-------+----------+ #|Alberto| 2| #| Dakota| 2| #+-------+----------+ #root # |-- Name: string (nullable = true) # |-- askdaosdka: long (nullable = true) df = data.selectExpr("Name as name", "askdaosdka as age") df.show() df.printSchema() # Output #+-------+---+ #| name|age| #+-------+---+ #|Alberto| 2| #| Dakota| 2| #+-------+---+ #root # |-- name: string (nullable = true) # |-- age: long (nullable = true) Option 2. Using withColumnRenamed, notice that this method allows you to "overwrite" the same column. For Python3, replace xrange with range. from functools import reduce oldColumns = data.schema.names newColumns = ["name", "age"] df = reduce(lambda data, idx: data.withColumnRenamed(oldColumns[idx], newColumns[idx]), xrange(len(oldColumns)), data) df.printSchema() df.show() Option 3. using alias, in Scala you can also use as. from pyspark.sql.functions import col data = data.select(col("Name").alias("name"), col("askdaosdka").alias("age")) data.show() # Output #+-------+---+ #| name|age| #+-------+---+ #|Alberto| 2| #| Dakota| 2| #+-------+---+ Option 4. Using sqlContext.sql, which lets you use SQL queries on DataFrames registered as tables. sqlContext.registerDataFrameAsTable(data, "myTable") df2 = sqlContext.sql("SELECT Name AS name, askdaosdka as age from myTable") df2.show() # Output #+-------+---+ #| name|age| #+-------+---+ #|Alberto| 2| #| Dakota| 2| #+-------+---+


from pyspark.sql.types import StructType,StructField, StringType, IntegerType

CreatingDataFrame = [("James","Sales","NY",90000,34,10000),
    ("Michael","Sales","NY",86000,56,20000),
    ("Robert","Sales","CA",81000,30,23000),
    ("Maria","Finance","CA",90000,24,23000),
    ("Raman","Finance","CA",99000,40,24000),
    ("Scott","Finance","NY",83000,36,19000),
    ("Jen","Finance","NY",79000,53,15000),
    ("Jeff","Marketing","CA",80000,25,18000),
    ("Kumar","Marketing","NY",91000,50,21000)
  ]

schema = StructType([ \
    StructField("employee_name",StringType(),True), \
    StructField("department",StringType(),True), \
    StructField("state",StringType(),True), \
    StructField("salary", IntegerType(), True), \
    StructField("age", StringType(), True), \
    StructField("bonus", IntegerType(), True) \
  ])

 
OurData = spark.createDataFrame(data=CreatingDataFrame,schema=schema)

OurData.show()

# COMMAND ----------

GrouppedBonusData=OurData.groupBy("department").sum("bonus")


# COMMAND ----------

GrouppedBonusData.show()


# COMMAND ----------

GrouppedBonusData.printSchema()

# COMMAND ----------

from pyspark.sql.functions import col

BonusColumnRenamed = GrouppedBonusData.select(col("department").alias("department"), col("sum(bonus)").alias("Total_Bonus"))
BonusColumnRenamed.show()

# COMMAND ----------

GrouppedBonusData.groupBy("department").count().show()

# COMMAND ----------

GrouppedSalaryData=OurData.groupBy("department").sum("salary")

# COMMAND ----------

GrouppedSalaryData.show()

# COMMAND ----------

from pyspark.sql.functions import col

SalaryColumnRenamed = GrouppedSalaryData.select(col("department").alias("Department"), col("sum(salary)").alias("Total_Salary"))
SalaryColumnRenamed.show()

df。withColumnRenamed(“年龄”、“age2”)