How Can I Efficiently Check for Value Existence in a Go List?

Checking Value Presence in a List in Go

In Python, the in keyword conveniently verifies if an element is present in a list. Go, on the other hand, lacks an explicit equivalent. This article explores techniques for implementing such a check in Go.

One approach involves using a set, which maps values to unused integer values. However, this requires an artificial integer specification for each element and isn't considered an ideal solution.

A more elegant approach is to leverage a map of strings to booleans. The map serves as a set, and the absence of a key-value pair in the map equates to false, which can be interpreted as the element not being in the list.

valid := map[string]bool{"red": true, "green": true, "yellow": true, "blue": true}

if valid[x] {
    fmt.Println("found")
} else {
    fmt.Println("not found")
}

Note:

For efficiency with large lists, consider either initializing the map using a for range loop or creating an untyped constant to optimize the boolean value assignment.

var t = true
valid := map[string]bool{"red": t, "green": t, "yellow": t, "blue": t}

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