---
title: "lookup"
description: "This looks for lookupValue in the lookupColumn of dataset."
---

# lookup

> This looks for lookupValue in the lookupColumn of dataset.

**This function is used by Ignition's Expression language.**
## Description
This looks for lookupValue in the lookupColumn of dataset. If it finds a match, it will return the value from the resultColumn on the same row as the match. If no match is found, noMatchValue is returned. 

:::note 
The type of the value returned will always be coerced to be the same type as the noMatchValue. 
:::

If lookupColumn is not specified, it defaults to 0. If resultColumn is not specified, it defaults to 1. 

## Syntax
`lookup(dataset, lookupValue, noMatchValue[, lookupColumn][, resultColumn])`

- Parameters

    - DataSet **dataset** - A dataset to search through.

    - object **lookupValue** - The value to look for.

    - object **noMatchValue** - The result value if no match.

    - object **lookupColumn** - Optional. The column to lookup. Can either be the column index or the name of the column.

    - object **resultColumn** - Optional. The column to pull the result value from. Can either be the column index or the name of the column.

- Results
    - object - The value in the result column of the same row that the lookupValue was found, or the noMatchValue if a match was not found. The data type of this object will always be coerced to match the type of the noMatchValue parameter. 

## Examples
The examples are based of a table that has the following data in it:

| Product | Price | Category |
|---|---|---|
| "Apples" |	1.99 |	"Fruit" |
| "Carrots |	3.5 |	"Vegetable" |
| "Walnuts" |	6.25 |	"Nut" |

```python title="Code Snippet"
lookup({Root Container.Table.data}, "Carrots", -1.0) //returns 3.50
```
```python title="Code Snippet"
lookup({Root Container.Table.data}, "Grapefruit", -1) //returns -1, the noMatchValue
```
```python title="Code Snippet"
lookup({Root Container.Table.data}, "Walnuts", "Unknown", 0, "Category") //returns "Nut"
```
```python title="Code Snippet"
lookup({Root Container.Table.data}, "Pecans", "Unknown", 0, 2) //returns "Unknown", the noMatchValue
```