如何在Spark数据框中将所有列更改为double类型 [英] How to change all columns to double type in a spark dataframe

问题描述

我正在尝试将spark数据帧的所有列更改为double类型，但我想知道是否有比仅循环遍历和强制转换更好的方法。

I am trying to change all the columns of a spark dataframe to double type but i want to know if there is a better way of doing it than just looping over the columns and casting.

推荐答案

使用此数据框：

df = spark.createDataFrame(
  [
    (1,2),
    (2,3),
  ],
  ["foo","bar"]
)

df.show()
+---+---+
|foo|bar|
+---+---+
|  1|  2|
|  2|  3|
+---+---+

循环可能是最简单，更自然的解决方案。

the for loop is problably the easiest and more natural solution.

from pyspark.sql import functions as F

for col in df.columns:
  df = df.withColumn(
    col,
    F.col(col).cast("double")
  )

df.show()
+---+---+
|foo|bar|
+---+---+
|1.0|2.0|
|2.0|3.0|
+---+---+

当然，您也可以使用python理解：

Of course, you can also use python comprehension:

df.select(
  *(
    F.col(col).cast("double").alias(col)
    for col
    in df.columns
  )
).show()

+---+---+
|foo|bar|
+---+---+
|1.0|2.0|
|2.0|3.0|
+---+---+

如果列很多，第二种解决方案要好一些。

If you have a lot of columns, the second solution is a little bit better.

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