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Version: Python

Ternary conditional operator (ternary-if)

The Deephaven Query Language (DQL) implements if-then-else logic using a one-line ternary conditional operator, also known as ternary-if.

The syntax for the ternary conditional operator is:

condition ? expressionIfTrue : expressionIfFalse

The question mark (?) separates the condition from the expressions, and the colon (:) separates the expression evaluated when the condition is true from the expression evaluated when the condition is false.

The expression x ? y : z evaluates as follows:

  • If x is true, the expression evaluates to y.
  • If x is false, the expression evaluates to z.

The expression x ? (y ? 1 : 2) : 3 evaluates as follows:

  • If both x and y are true, the expression evaluates to 1.
  • If x is true, and y is false, the expression evaluates to 2.
  • If x is false, the expression evaluates to 3.

Syntax

condition ? expressionTrue : expressionFalse

Parameters

ParameterTypeDescription
conditionboolean

The condition to be evaluated.

expressionTrueexpression

If condition is true, the result of this expression will be returned.

expressionFalseexpression

If condition is false, the result of this expression will be returned.

Returns

expressionTrue if condition is true, and expressionFalse if condition is false.

Examples

In the following example, a new column, Budget, is created. The column contains yes, if the value in the Price column is less than or equal to 3.50, and contains no otherwise.

from deephaven import new_table

from deephaven.column import string_col, int_col, double_col

source = new_table([
string_col("Type", ["Pine", "Fir", "Cedar", "Oak", "Ash", "Walnut", "Beech", "Cherry"]),
string_col("Hardness", ["soft", "soft", "soft", "hard", "hard", "hard", "hard", "hard"]),
double_col("Price", [1.95, 3.70, 3.25, 3.45, 4.25, 7.95 , 4.10, 5.25])
])

result = source.update(formulas=["Budget = (Price <= 3.50) ? `yes` : `no` "])

In the following example, a ternary-if is used to categorize woods into three categories:

  • hard-cheap: hardwoods costing less than or equal to $3.50,
  • hard-expensive: hardwoods costing more than $3.50, and
  • soft: softwoods.
from deephaven import new_table
from deephaven.column import string_col, int_col, double_col

source = new_table([
string_col("Type", ["Pine", "Fir", "Cedar", "Oak", "Ash", "Walnut", "Beech", "Cherry"]),
string_col("Hardness", ["soft", "soft", "soft", "hard", "hard", "hard", "hard", "hard"]),
double_col("Price", [1.95, 3.70, 3.25, 3.45, 4.25, 7.95 , 4.10, 5.25])
])

result = source.update(formulas=[
"Category = (Hardness == `hard`) ? ( (Price <= 3.50) ? `hard-cheap` : `hard-expensive` ) : `soft` "])