I am trying to achieve below polars expression :

pl.when(pl.col(a).contains("some value")).then(pl.concat_list("ArayColumn"),[A])
  .when(pl.col(a).contains("some value")).then(pl.concat_list("ArayColumn"),[B])
  .when(pl.col(a).contains("some value")).then(pl.concat_list("ArayColumn"),[C])
  .otherwise("Z is Big").alias("Bigger Value")

But i would like to generate those expressions in-dynamic means :

exprs = []
for i,value on conditions: 
  exprs.append(pl.when(i).then(value))

exprs.otherwise(defaultValue).alias("Bigger Value")

i want to apply exprs on a data frame, like below:

dataFrame.with_columns(exprs).

so, i want for each row, it should first when, then, second when, then…..
i should evaluate every when.then condition and union all

my final values may contain [A, B, C].

Tried Approaches :

1. For Loop and applying one by one , but if dataFrame has huge data its blasting.
2. Expression chaining , but polars otherwise is taking None by default for every conditions i kept and making it slow [ few ms ]

can you suggest me any other approach ? I need to generate the expression and later i will apply on dataFrame.