---
title: "system.mongodb.findOne"
description: "Returns a single PyDictionary that matches the criteria specified on the filter parameter."
---

# system.mongodb.findOne

> Returns a single PyDictionary that matches the criteria specified on the filter parameter.

This function is used in **Python Scripting**.

:::note
Project Library scripts will not provide hints for MongoDB system functions unless the Script Hint Scope is set to **Gateway**. See the [Scripting in Ignition](platform\scripting\scripting-in-ignition\scripting-in-ignition.md#system-functions-hints-and-autocomplete) page for more details on scripting hints.
:::

## Description
## Client Permission Restrictions
This scripting function has no [Client Permission](../../../ignition-modules/vision/vision-project-properties/vision-project-properties.md#vision-permissions-properties) restrictions.

## Syntax
`system.mongodb.findOne(connector, collection, filter, [projection])`

### Parameters
Type | Parameter | Description 
------- | ------- | ------
String| `connector` | The name of connector (case-insensitive).
String| `collection` | The name of collection (case-sensitive).
PyDictionary| `filter` | A PyDictionary for specifying matching key value pair criteria when querying a collection.
PyDictionary| `projection` | A PyDictionary for including or omitting specific key value pairs in the query result. [See MongoDB documentation](https://www.mongodb.com/docs/manual/tutorial/project-fields-from-query-results/) for all valid project values. [optional]

### Returns
**PyDictionary** `result` - A single PyDictionary as a result.

### Scope
Gateway, Perspective Session

## Importing Classes
You can import classes from system.mongodb.types like you would other Python classes:

#### Example
```
from system.mongodb.types import ObjectId
 
newObjectId = ObjectId.get()
```

You can also iterate those system.mongodb.types packages to see all available classes:

#### Example
```
for d in dir(system.mongodb.types):
    print d
```

### API Docs
MongoDB-specific data types come from the org.bson.types package of the Mongo Java Driver API. The library of classes available for import can be accessed at this link: [Mongo Java Driver 3.6.0 API Docs for Package org.bson.types](https://mongodb.github.io/mongo-java-driver/3.6/javadoc/org/bson/types/package-summary.html).

## Types References
The following values can be referenced for the types parameter at system.mongodb.types:
```
Binary
Code
CodeWScope
CodeWithScope
Decimal128
INSTANCE
MaxKey
MinKey
ObjectId
Symbol
Timestamp
```

## Code Examples
```python title="Example #1"
# Retrieve a both a connector name and collection name to query from.
connector = system.mongodb.listConnectorInfo()[0]['name']
collection = system.mongodb.listCollectionNames(connector)[0]    
 
 
# Specify unique field values to locate specific document.
filter = {"qualityControlProcess":"V020"}
project = {"_id":1, "position":1,"elevation":1,"type":1}
  
# Apply parameters for function call.
document = system.mongodb.findOne(connector, collection, filter, project)
  
# Print the result. Here it is expected that all key value pairs specified in the project parameter will be available.
print "Document ID: " + str(document["_id"])
print "Type: " + str(document["type"])
print "Position: " + str(document["position"])
print "Elevation: " + str(document["elevation"])
```