PySpark:when 子句中有多个条件 [英] PySpark: multiple conditions in when clause

问题描述

我想修改当前为空白的数据框列 (Age) 的单元格值，并且只有在另一列 (Survived) 的相应行的值为 0 时才执行此操作，其中年龄为空白.如果它在 Survived 列中为 1 但在 Age 列中为空白，那么我将其保留为空.

I would like to modify the cell values of a dataframe column (Age) where currently it is blank and I would only do it if another column (Survived) has the value 0 for the corresponding row where it is blank for Age. If it is 1 in the Survived column but blank in Age column then I will keep it as null.

我尝试使用 && 运算符，但没有用.这是我的代码:

I tried to use && operator but it didn't work. Here is my code:

tdata.withColumn("Age",  when((tdata.Age == "" && tdata.Survived == "0"), mean_age_0).otherwise(tdata.Age)).show()

任何建议如何处理?谢谢.

Any suggestions how to handle that? Thanks.

错误信息:

SyntaxError: invalid syntax
  File "<ipython-input-33-3e691784411c>", line 1
    tdata.withColumn("Age",  when((tdata.Age == "" && tdata.Survived == "0"), mean_age_0).otherwise(tdata.Age)).show()
                                                    ^

推荐答案

你得到 SyntaxError 错误异常，因为 Python 没有 && 操作符.它有 and 和 & ，后者是在 Column (|用于逻辑析取，~ 用于逻辑否定).

You get SyntaxError error exception because Python has no && operator. It has and and & where the latter one is the correct choice to create boolean expressions on Column (| for a logical disjunction and ~ for logical negation).

您创建的条件也无效，因为它不考虑运算符优先级.& 在 Python 中比 == 有更高的优先级，所以表达式必须用括号括起来.

Condition you created is also invalid because it doesn't consider operator precedence. & in Python has a higher precedence than == so expression has to be parenthesized.

(col("Age") == "") & (col("Survived") == "0")
## Column<b'((Age = ) AND (Survived = 0))'>

附注 when 函数等价于 case 表达式而不是 WHEN 子句.仍然适用相同的规则.连词:

On a side note when function is equivalent to case expression not WHEN clause. Still the same rules apply. Conjunction:

df.where((col("foo") > 0) & (col("bar") < 0))

分离:

df.where((col("foo") > 0) | (col("bar") < 0))

您当然可以单独定义条件以避免括号:

You can of course define conditions separately to avoid brackets:

cond1 = col("Age") == "" 
cond2 = col("Survived") == "0"

cond1 & cond2

这篇关于PySpark:when 子句中有多个条件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！