title: Truncate a string with pyspark
body: <p>I am currently working on PySpark with Databricks and I was looking for a way to truncate a string just like the excel right function does.
  For example, I would like to change for an ID column in a <code>DataFrame</code> <code>8841673_3</code> into <code>8841673</code>.</p>
  
  <p>Does anybody knows how I should proceed?</p>