skrub.Expr.skb.if_else#

Expr.skb.if_else(value_if_true, value_if_false)[source]#

Create a conditional expression.

If self evaluates to True, the result will be value_if_true, otherwise value_if_false.

The branch which is not selected is not evaluated, which is the main advantage compared to wrapping the conditional statement in a @skrub.deferred function.

Parameters:

value_if_true: The value to return if self is true.
value_if_false: The value to return if self is false.

Returns:

Conditional expression

See also

skrub.Expr.skb.match: Select based on the value of an expression.

Examples

>>> import skrub
>>> import numpy as np
>>> a = skrub.var('a')
>>> shuffle_a = skrub.var('shuffle_a')

>>> @skrub.deferred
... def shuffled(values):
...     print('shuffling')
...     return np.random.default_rng(0).permutation(values)

>>> @skrub.deferred
... def copy(values):
...     print('copying')
...     return values.copy()

>>> b = shuffle_a.skb.if_else(shuffled(a), copy(a))
>>> b
<IfElse <Var 'shuffle_a'> ? <Call 'shuffled'> : <Call 'copy'>>

Note that only one of the 2 branches is evaluated:

>>> b.skb.eval({'a': np.arange(3), 'shuffle_a': True})
shuffling
array([2, 0, 1])
>>> b.skb.eval({'a': np.arange(3), 'shuffle_a': False})
copying
array([0, 1, 2])

skrub.Expr.skb.if_else#

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