#Function
In PySpark, when().otherwise() is used for conditional column expressions, similar to SQL CASE WHEN.

Syntax: -

from pyspark.sql.functions import when

new_col = when(condition, value_if_true).otherwise(value_if_false)

Example: -

df = df.withColumn("new_col", when(col("age") > 18, "Adult").otherwise("Minor"))

Can be used to update existing columns, handling null values etc.

# Apply multiple conditions
df_with_conditions = df.withColumn(
    "category_label",
    when(col("category") == "A", "Label 1")
    .when(col("category") == "B", "Label 2")
    .when(col("category") == "C", "Label 3")
    .otherwise("Other")
)