---
title: "replace"
description: "Finds all occurrences of a substring inside of a source string, and replaces them with the replacement string."
---

# replace

> Finds all occurrences of a substring inside of a source string, and replaces them with the replacement string.

**This function is used by Ignition's Expression language.**

## Description
Finds all occurrences of a substring inside of a source string, and replaces them with the replacement string. The first argument is the source, the second is the search string, and the third is the replacement.

## Syntax
`replace(string, substring, replacementString)`

### Parameters

| Type | Parameter | Description |
|---|---|---|
| String | `string` | The starting string. |
| String | `substring` | The string to search for. |
| String | `replacementString` | The string to replace any instances of the substring with. |

### Results
**String** - The starting string with all instances of the substring replaced by the replacementString.

## Examples
```python title="Code Snippet"
replace("XYZ", "Y", "and") //returns "XandZ"
```
```python title="Code Snippet"
replace("bob and mary went to bob's house", "bob", "judith") //returns "judith and mary went to judith's house"
```