Python 使用列的长度筛选数据帧
我想使用与列长度相关的条件过滤Python 使用列的长度筛选数据帧,python,apache-spark,dataframe,pyspark,apache-spark-sql,Python,Apache Spark,Dataframe,Pyspark,Apache Spark Sql,我想使用与列长度相关的条件过滤DataFrame,这个问题可能很简单,但我在SO中没有找到任何相关问题 更具体地说,我有一个DataFrame只有一个列其中的ArrayType(StringType()),我想用长度作为过滤器过滤DataFrame,我在下面截取了一个片段 df = sqlContext.read.parquet("letters.parquet") df.show() # The output will be # +------------+ # | tokens
DataFrame
,这个问题可能很简单,但我在SO中没有找到任何相关问题
更具体地说,我有一个DataFrame
只有一个列
其中的ArrayType(StringType())
,我想用长度作为过滤器过滤DataFrame
,我在下面截取了一个片段
df = sqlContext.read.parquet("letters.parquet")
df.show()
# The output will be
# +------------+
# | tokens|
# +------------+
# |[L, S, Y, S]|
# |[L, V, I, S]|
# |[I, A, N, A]|
# |[I, L, S, A]|
# |[E, N, N, Y]|
# |[E, I, M, A]|
# |[O, A, N, A]|
# | [S, U, S]|
# +------------+
# But I want only the entries with length 3 or less
fdf = df.filter(len(df.tokens) <= 3)
fdf.show() # But it says that the TypeError: object of type 'Column' has no len(), so the previous statement is obviously incorrect.
df=sqlContext.read.parquet(“letters.parquet”)
df.show()
#输出将是
# +------------+
#|代币|
# +------------+
#|[L,S,Y,S]|
#|[L,V,I,S]|
#|[I,A,N,A]|
#|[I,L,S,A]|
#|[E,N,N,Y]|
#|[E,I,M,A]|
#|[O,A,N,A]|
#|[S,U,S]|
# +------------+
#但我只想要长度小于等于3的条目
fdf=df.filter(len(df.tokens)在Spark>=1.5中,您可以使用以下函数:
from pyspark.sql.functions import col, size
df = sqlContext.createDataFrame([
(["L", "S", "Y", "S"], ),
(["L", "V", "I", "S"], ),
(["I", "A", "N", "A"], ),
(["I", "L", "S", "A"], ),
(["E", "N", "N", "Y"], ),
(["E", "I", "M", "A"], ),
(["O", "A", "N", "A"], ),
(["S", "U", "S"], )],
("tokens", ))
df.where(size(col("tokens")) <= 3).show()
## +---------+
## | tokens|
## +---------+
## |[S, U, S]|
## +---------+
from pyspark.sql.functions import length
df = sqlContext.createDataFrame([("fooo", ), ("bar", )], ("k", ))
df.where(length(col("k")) <= 3).show()
## +---+
## | k|
## +---+
## |bar|
## +---+
对于字符串列,您可以使用上面定义的udf
或length
函数:
from pyspark.sql.functions import col, size
df = sqlContext.createDataFrame([
(["L", "S", "Y", "S"], ),
(["L", "V", "I", "S"], ),
(["I", "A", "N", "A"], ),
(["I", "L", "S", "A"], ),
(["E", "N", "N", "Y"], ),
(["E", "I", "M", "A"], ),
(["O", "A", "N", "A"], ),
(["S", "U", "S"], )],
("tokens", ))
df.where(size(col("tokens")) <= 3).show()
## +---------+
## | tokens|
## +---------+
## |[S, U, S]|
## +---------+
from pyspark.sql.functions import length
df = sqlContext.createDataFrame([("fooo", ), ("bar", )], ("k", ))
df.where(length(col("k")) <= 3).show()
## +---+
## | k|
## +---+
## |bar|
## +---+
从pyspark.sql.functions导入长度
df=sqlContext.createDataFrame([(“fooo”,),(“bar”,)],(“k”,))
df.where(length(col(“k”))这里是scala中字符串的一个示例:
val stringData = Seq(("Maheswara"), ("Mokshith"))
val df = sc.parallelize(stringData).toDF
df.where((length($"value")) <= 8).show
+--------+
| value|
+--------+
|Mokshith|
+--------+
df.withColumn("length", length($"value")).show
+---------+------+
| value|length|
+---------+------+
|Maheswara| 9|
| Mokshith| 8|
+---------+------+
val stringData=Seq((“Maheswara”),(“Mokshith”))
val df=sc.parallelize(stringData).toDF
df.where((长度($“值”)@AlbertoBonsanto:下面是基于数组大小的代码过滤器:
val input = Seq(("a1,a2,a3,a4,a5"), ("a1,a2,a3,a4"), ("a1,a2,a3"), ("a1,a2"), ("a1"))
val df = sc.parallelize(input).toDF("tokens")
val tokensArrayDf = df.withColumn("tokens", split($"tokens", ","))
tokensArrayDf.show
+--------------------+
| tokens|
+--------------------+
|[a1, a2, a3, a4, a5]|
| [a1, a2, a3, a4]|
| [a1, a2, a3]|
| [a1, a2]|
| [a1]|
+--------------------+
tokensArrayDf.filter(size($"tokens") > 3).show
+--------------------+
| tokens|
+--------------------+
|[a1, a2, a3, a4, a5]|
| [a1, a2, a3, a4]|
+--------------------+
如果列是一个字符串
,而我假装按字符串
的长度进行过滤,那该怎么办?相同的udf或长度
函数。我的问题与此不同,我指的是一个字符串数组的列。