将Spark DataFrame列转换为python列表 [英] Convert spark DataFrame column to python list

问题描述

我在一个包含两列mvv和count的数据帧上工作.

I work on a dataframe with two column, mvv and count.

+---+-----+
|mvv|count|
+---+-----+
| 1 |  5  |
| 2 |  9  |
| 3 |  3  |
| 4 |  1  |

我想获得两个包含mvv值和计数值的列表.像

i would like to obtain two list containing mvv values and count value. Something like

mvv = [1,2,3,4]
count = [5,9,3,1]

因此，我尝试了以下代码:第一行应返回python行的列表.我想看第一个值:

So, I tried the following code: The first line should return a python list of row. I wanted to see the first value:

mvv_list = mvv_count_df.select('mvv').collect()
firstvalue = mvv_list[0].getInt(0)

但是我在第二行收到一条错误消息:

But I get an error message with the second line:

AttributeError:getInt

AttributeError: getInt

推荐答案

请参阅为什么您这样做的方式不起作用.首先，您尝试从行类型，收集的输出如下:

See, why this way that you are doing is not working. First, you are trying to get integer from a Row Type, the output of your collect is like this:

>>> mvv_list = mvv_count_df.select('mvv').collect()
>>> mvv_list[0]
Out: Row(mvv=1)

如果您采取这样的做法:

If you take something like this:

>>> firstvalue = mvv_list[0].mvv
Out: 1

您将获得mvv值.如果您需要数组的所有信息，则可以采取以下方法:

You will get the mvv value. If you want all the information of the array you can take something like this:

>>> mvv_array = [int(row.mvv) for row in mvv_list.collect()]
>>> mvv_array
Out: [1,2,3,4]

但是，如果对另一列尝试相同的操作，则会得到:

But if you try the same for the other column, you get:

>>> mvv_count = [int(row.count) for row in mvv_list.collect()]
Out: TypeError: int() argument must be a string or a number, not 'builtin_function_or_method'

之所以会发生这种情况，是因为count是内置方法.并且该列与count同名.一种解决方法是将count的列名更改为_count:

This happens because count is a built-in method. And the column has the same name as count. A workaround to do this is change the column name of count to _count:

>>> mvv_list = mvv_list.selectExpr("mvv as mvv", "count as _count")
>>> mvv_count = [int(row._count) for row in mvv_list.collect()]

但是不需要此解决方法，因为您可以使用字典语法访问列:

But this workaround is not needed, as you can access the column using the dictionary syntax:

>>> mvv_array = [int(row['mvv']) for row in mvv_list.collect()]
>>> mvv_count = [int(row['count']) for row in mvv_list.collect()]

它最终将起作用！

这篇关于将Spark DataFrame列转换为python列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！