使用负索引从pyspark字符串列的最后一个索引中子字符串化多个字符 [英] substring multiple characters from the last index of a pyspark string column using negative indexing

问题描述

与以下内容密切相关:

Closely related to: Spark Dataframe column with last character of other column but I want to extract multiple characters from the -1 index.

我有以下pyspark数据框df

I have the following pyspark dataframe df

+----------+----------+
|    number|event_type|
+----------+----------+
|0342224022|        11|
|0112964715|        11|
+----------+----------+

我想从number列的最后一个索引中提取3个字符.

I want to extract 3 characters from the last index of the number column.

我尝试了以下操作:

from pyspark.sql.functions import substring 
df.select(substring(df['number'], -1, 3), 'event_type').show(2)

# which returns:

+----------------------+----------+
|substring(number,-1,3)|event_type|
+----------------------+----------+
|                     2|        11|
|                     5|        11|
+----------------------+----------+

以下是预期的输出(我不确定上面的输出是什么):

The below is the expected output (and I'm not sure what the output above is):

+----------------------+----------+
|substring(number,-1,3)|event_type|
+----------------------+----------+
|                   022|        11|
|                   715|        11|
+----------------------+----------+

我在做什么错了?

注意:Spark版本1.6.0

Note: Spark version 1.6.0

推荐答案

这是您使用

This is how you use substring. Your position will be -3 and the length is 3.

pyspark.sql.functions.substring(str, pos, len)

您需要将子字符串函数调用更改为:

You need to change your substring function call to:

from pyspark.sql.functions import substring
df.select(substring(df['number'], -3, 3), 'event_type').show(2)
#+------------------------+----------+
#|substring(number, -3, 3)|event_type|
#+------------------------+----------+
#|                     022|        11|
#|                     715|        11|
#+------------------------+----------+

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