from pyspark.sql.functions import *

# Example 1
fact_df = fact_df.withColumn('colname', trim(col('colname'))).alias('fact_df')

# Example 2
fact_df = fact_df.join(dimension_df, trim(col('fact_df.colname') == trim(col('dimension_df.another_colname')), 'left').alias('fact_df')