Spark - 从 DataFrame 中提取单个值

Question

I have a Spark DataFrame query that is guaranteed to return single column with single Int value. What is the best way to extract this value as Int from the resulting DataFrame?

Answer 1

You can use head

df.head().getInt(0)

or first

df.first().getInt(0)

Check DataFrame scala docs for more details

Answer 2

This could solve your problem.

df.map{
    row => row.getInt(0)
}.first()

Answer 3

在Pyspark ，如果dataframe是具有one column作为响应的单个实体，则您可以简单地获取第一个元素，否则，将返回一整row ，然后您必须获得dimension-wise响应，即df.head()[0][0]

df.head()[0]

Answer 4

If we have the spark dataframe as :

+----------+
|_c0       |
+----------+
|2021-08-31|
+----------+

x = df.first()[0]
print(x)

2021-08-31