fiftyone.core.stages.SetField

Sets a field or embedded field on each sample in a collection by evaluating the given expression.

This method can process embedded list fields. To do so, simply append [] to any list component(s) of the field path.

The provided expr is interpreted relative to the document on which the embedded field is being set. For example, if you are setting a nested field field="embedded.document.field", then the expression expr you provide will be applied to the embedded.document document. Note that you can override this behavior by defining an expression that is bound to the root document by prepending "$" to any field name(s) in the expression.

See the examples below for more information.

Examples:

import fiftyone as fo
import fiftyone.zoo as foz
from fiftyone import ViewField as F

dataset = foz.load_zoo_dataset("quickstart")

#
# Replace all values of uniqueness that are less than 0.5 with `None`
#

stage = fo.SetField(
    "uniqueness",
    (F("uniqueness") >= 0.5).if_else(F("uniqueness"), None)
)
view = dataset.add_stage(stage)
print(view.bounds("uniqueness"))

#
# Lower bound all object confidences in the `predictions` field by 0.5
#

stage = fo.SetField(
    "predictions.detections.confidence", F("confidence").max(0.5)
)
view = dataset.add_stage(stage)
print(view.bounds("predictions.detections.confidence"))

#
# Add a `num_predictions` property to the `predictions` field that
# contains the number of objects in the field
#

stage = fo.SetField(
    "predictions.num_predictions",
    F("$predictions.detections").length(),
)
view = dataset.add_stage(stage)
print(view.bounds("predictions.num_predictions"))

#
# Set an `is_animal` field on each object in the `predictions` field
# that indicates whether the object is an animal
#

ANIMALS = [
    "bear", "bird", "cat", "cow", "dog", "elephant", "giraffe",
    "horse", "sheep", "zebra"
]

stage = fo.SetField(
    "predictions.detections.is_animal", F("label").is_in(ANIMALS)
)
view = dataset.add_stage(stage)
print(view.count_values("predictions.detections.is_animal"))