我正在对Dataframe的多个列执行ltrim和rtrim，但现在我可以单独执行了。喜欢

# selected_colums = selected_colums.withColumn("last_name", ltrim(selected_colums.last_name))

# selected_colums = selected_colums.withColumn("last_name", rtrim(selected_colums.last_name))

# selected_colums = selected_colums.withColumn("email", ltrim(selected_colums.email))

# selected_colums = selected_colums.withColumn("email", rtrim(selected_colums.email))

# selected_colums = selected_colums.withColumn("phone_number", ltrim(selected_colums.phone_number))

# selected_colums = selected_colums.withColumn("phone_number", rtrim(selected_colums.phone_number))

但我想像下面这样循环

sdk = ['first_name','last_name','email','phone_number','email_alt','phone_number_alt']
for x in sdk:
  selected_colums = selected_colums.withColumn(x, ltrim(selected_colums.last_name))

它给了我语法错误。请帮我优化这段代码，这样对于任何数量的列我都可以做ltrim或rtrim只是传递列表。