EntityList
Listing of Entity Types »EntityList[class]
gives a list of entities in the specified entity class.
EntityList["type"]
gives a list of entities of the specified type.
EntityList[class,simplify]
gives a list of entities; simplify determines whether to reduce entities to the simplest possible type.
Details
- In EntityList[class], class can be one of the following:
-
EntityClass representation of a table or virtual table in a database FilteredEntityClass entity class filtered by a criterion SortedEntityClass entity class sorted by properties or functions SampledEntityClass entity class formed by sampling a number of entities ExtendedEntityClass entity class with properties added for each entity AggregatedEntityClass entity class formed by aggregating entities CombinedEntityClass entity class formed by combining properties across entity classes - EntityList["type"] is systematically supported only for types allowing a fixed number of entities.
- EntityList[class] is effectively equivalent to EntityList[class,True].
- When reducing entities to their base type, the outermost layers of EntityClass, FilteredEntityClass, SortedEntityClass and SampledEntityClass can be removed; anything else must be kept.
Examples
open all close allBasic Examples (4)
EntityList[EntityClass["Country", "Countries"]]//ShallowEntityList["Planet"]EntityList can also be used on EntityClass expressions:
EntityClassList["Volcano"]EntityList[EntityClass["Volcano", "Supervolcanos"]]EntityList can be used on many types of entity classes:
EntityList[FilteredEntityClass["Country", EntityFunction[c, c["Population"] > Quantity[1*10^8, "People"] && c["Continent"] == EntityClass["Country", "Africa"]]]]Use EntityList with a second argument to decide whether to simplify the entities:
EntityList[FilteredEntityClass["Country", EntityFunction[c, c["Population"] > Quantity[1*10^8, "People"] && c["Continent"] == EntityClass["Country", "Africa"]]], False]Scope (2)
EntityList can also be used on EntityClass expressions:
EntityClassList["Volcano"]EntityList[EntityClass["Volcano", "Supervolcanos"]]Some entity classes cannot be simplified:
EntityList[ExtendedEntityClass["Planet", "kepler" -> EntityFunction[p, p[EntityProperty["Planet", "OrbitPeriod"]] ^ 2 / p[EntityProperty["Planet", "SemimajorAxis"]] ^ 3]]]Properties & Relations (6)
EntityList can be used with FilteredEntityClass:
EntityList[FilteredEntityClass["Planet", EntityFunction[p, p["Mass"] > Quantity[1*10^25, "Kilograms"]]]]EntityList can be used with SampledEntityClass:
EntityList[SampledEntityClass["Cloud", 2]]EntityList can be used with SortedEntityClass:
EntityList[SortedEntityClass["Dinosaur", EntityProperty["Dinosaur", "Weight"] -> "Descending", 3]]EntityList can be used with ExtendedEntityClass, but it will not simplify:
EntityList[ExtendedEntityClass["Dinosaur", "BMI" -> EntityFunction[d, d["Weight"] / d["Length"] ^ 2]]]//ShortWhen other heads that can be simplified appear around ExtendedEntityClass, they will be simplified:
EntityList[SortedEntityClass[ExtendedEntityClass["Dinosaur", "BMI" -> EntityFunction[d, d["Weight"] / d["Length"] ^ 2]], "BMI" -> "Descending", 3]]EntityList can be used with AggregatedEntityClass, but it will not simplify:
EntityList[AggregatedEntityClass["Country", "Population" -> Total, "Continent"]]EntityList can be used with CombinedEntityClass, but it will not simplify:
EntityList[CombinedEntityClass[ EntityClass["Element", "Period1"], "Isotope", "Entity" -> "Element"]]Possible Issues (3)
In general, it is best to avoid calling EntityList before EntityValue, as two separate calls will have to be performed:
EntityRegister[EntityStore[RelationalDatabase[FindFile["ExampleData/ecommerce-database.sqlite"]]]]This will have consequences in performance, and also in atomicity when dealing with external databases:
EntityValue["employees", "lastName"]//RepeatedTimingEntityValue[EntityList["employees"], "lastName"]//RepeatedTimingWhen EntityList returns a list of Entity objects with complex first arguments, those might stop existing if the data changes:
EntityRegister[EntityStore["t" -> <|
"Entities" -> <|
"e1" -> <|"p1" -> 17, "p2" -> 59|>,
"e2" -> <|"p1" -> 27, "p2" -> 288|>
|>
|>]]ents = EntityList[ExtendedEntityClass[EntityClass["t", "p1" -> GreaterThan[20]], "square" -> EntityFunction[t, t["p1"] ^ 2]]]EntityValue[ents, "p1"]Update the value of "p1" so that the condition is no longer met:
Entity["t", "e2"]["p1"] = 15EntityValue[ents, "p1"]When dealing with external databases, one might encounter a database where the primary key was not set for some tables:
EntityRegister[EntityStore[RelationalDatabase[URLDownload[CloudObject["https://www.wolframcloud.com/obj/documentation/nopk.sqlite"]]]]]
When this happens, EntityStore will emit a message. This means that some functionality involving single entities will be disabled:
EntityList["table"]
But EntityValue will generally keep working:
EntityValue["table", "col"]The only way around this problem is to set the primary key constraint in the external database.
Fast Introduction for Programmers: Real
An Elementary Introduction to the Wolfram LanguageText
Wolfram Research (2014), EntityList, Wolfram Language function, https://reference.wolfram.com/language/ref/EntityList.html (updated 2019).
CMS
Wolfram Language. 2014. "EntityList." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2019. https://reference.wolfram.com/language/ref/EntityList.html.
APA
Wolfram Language. (2014). EntityList. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/EntityList.html