# FlatMap class
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map"></a>

 Applies a transform to each `DynamicFrame` in a collection. Results are not flattened into a single `DynamicFrame`, but preserved as a collection. 

## Examples for FlatMap
<a name="aws-glue-api-crawler-pyspark-flat-map-examples"></a>

 The following example snippet demonstrates how to use the `ResolveChoice` transform on a collection of dynamic frames when applied to a `FlatMap`. The data used for input is in the JSON located at the placeholder Amazon S3 address `s3://bucket/path-for-data/sample.json` and contains the following data. 

### Example JSON data
<a name="aws-glue-api-crawler-pyspark-flat-map-examples-json"></a>

```
[{
    "firstname": "Arnav",
    "lastname": "Desai",
    "address": {
        "street": "6 Anyroad Avenue",
        "city": "London",
        "state": "England",
        "country": "UK"
    },
    "phone": 17235550101,
    "affiliations": [
        "General Anonymous Example Products",
        "Example Independent Research",
        "Government Department of Examples"
    ]
},
{
    "firstname": "Mary",
    "lastname": "Major",
    "address": {
        "street": "7821 Spot Place",
        "city": "Centerville",
        "state": "OK",
        "country": "US"
    },
    "phone": 19185550023,
    "affiliations": [
        "Example Dot Com",
        "Example Independent Research",
        "Example.io"
    ]
},
{
    "firstname": "Paulo",
    "lastname": "Santos",
    "address": {
        "street": "123 Maple Street",
        "city": "London",
        "state": "Ontario",
        "country": "CA"
    },
    "phone": 12175550181,
    "affiliations": [
        "General Anonymous Example Products",
        "Example Dot Com"
    ]
}]
```

**Example Apply ResolveChoice to a DynamicFrameCollection and show output.**  

```
#Read DynamicFrame
datasource = glueContext.create_dynamic_frame_from_options("s3", connection_options = {"paths":["s3://bucket/path/to/file/mysamplejson.json"]}, format="json")
datasource.printSchema()
datasource.show()

## Split to create a DynamicFrameCollection
split_frame=datasource.split_fields(["firstname","lastname","address"],"personal_info","business_info")
split_frame.keys()
print("---")

## Use FlatMap to run ResolveChoice
kwargs = {"choice": "cast:string"}
flat = FlatMap.apply(split_frame, ResolveChoice, frame_name="frame", transformation_ctx='tcx', **kwargs)
flat.keys()

##Select one of the DynamicFrames
personal_info = flat.select("personal_info")
personal_info.printSchema()
personal_info.show()
print("---")

business_info = flat.select("business_info")
business_info.printSchema()
business_info.show()
```
 When calling `FlatMap.apply`, the `frame_name` parameter **must** be `"frame"`. No other value is currently accepted. 

### Example output
<a name="aws-glue-api-crawler-pyspark-flat-map-examples"></a>

```
root
|-- firstname: string
|-- lastname: string
|-- address: struct
|    |-- street: string
|    |-- city: string
|    |-- state: string
|    |-- country: string
|-- phone: long
|-- affiliations: array
|    |-- element: string
---
{
    "firstname": "Mary",
    "lastname": "Major",
    "address": {
        "street": "7821 Spot Place",
        "city": "Centerville",
        "state": "OK",
        "country": "US"
    },
    "phone": 19185550023,
    "affiliations": [
        "Example Dot Com",
        "Example Independent Research",
        "Example.io"
    ]
}

{
    "firstname": "Paulo",
    "lastname": "Santos",
    "address": {
        "street": "123 Maple Street",
        "city": "London",
        "state": "Ontario",
        "country": "CA"
    },
    "phone": 12175550181,
    "affiliations": [
        "General Anonymous Example Products",
        "Example Dot Com"
    ]
}
---
root
|-- firstname: string
|-- lastname: string
|-- address: struct
|    |-- street: string
|    |-- city: string
|    |-- state: string
|    |-- country: string

{
    "firstname": "Mary",
    "lastname": "Major",
    "address": {
        "street": "7821 Spot Place",
        "city": "Centerville",
        "state": "OK",
        "country": "US"
    }
}

{
    "firstname": "Paulo",
    "lastname": "Santos",
    "address": {
        "street": "123 Maple Street",
        "city": "London",
        "state": "Ontario",
        "country": "CA"
    }
}
---
root
|-- phone: long
|-- affiliations: array
|    |-- element: string

{
    "phone": 19185550023,
    "affiliations": [
        "Example Dot Com",
        "Example Independent Research",
        "Example.io"
    ]
}

{
    "phone": 12175550181,
    "affiliations": [
        "General Anonymous Example Products",
        "Example Dot Com"
    ]
}
```

## Methods
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-_methods"></a>
+ [\$1\$1call\$1\$1](#aws-glue-api-crawler-pyspark-transforms-flat-map-__call__)
+ [Apply](#aws-glue-api-crawler-pyspark-transforms-flat-map-apply)
+ [Name](#aws-glue-api-crawler-pyspark-transforms-flat-map-name)
+ [describeArgs](#aws-glue-api-crawler-pyspark-transforms-flat-map-describeArgs)
+ [describeReturn](#aws-glue-api-crawler-pyspark-transforms-flat-map-describeReturn)
+ [describeTransform](#aws-glue-api-crawler-pyspark-transforms-flat-map-describeTransform)
+ [describeErrors](#aws-glue-api-crawler-pyspark-transforms-flat-map-describeErrors)
+ [Describe](#aws-glue-api-crawler-pyspark-transforms-flat-map-describe)

## \$1\$1call\$1\$1(dfc, BaseTransform, frame\$1name, transformation\$1ctx = "", \$1\$1base\$1kwargs)
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-__call__"></a>

Applies a transform to each `DynamicFrame` in a collection and flattens the results.
+ `dfc` – The `DynamicFrameCollection` over which to flatmap (required).
+ `BaseTransform` – A transform derived from `GlueTransform` to apply to each member of the collection (required).
+ `frame_name` – The argument name to pass the elements of the collection to (required).
+ `transformation_ctx` – A unique string that is used to identify state information (optional).
+ `base_kwargs` – Arguments to pass to the base transform (required).

Returns a new `DynamicFrameCollection` created by applying the transform to each `DynamicFrame` in the source `DynamicFrameCollection`.

## apply(cls, \$1args, \$1\$1kwargs)
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-apply"></a>

Inherited from `GlueTransform` [apply](aws-glue-api-crawler-pyspark-transforms-GlueTransform.md#aws-glue-api-crawler-pyspark-transforms-GlueTransform-apply).

## name(cls)
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-name"></a>

Inherited from `GlueTransform` [name](aws-glue-api-crawler-pyspark-transforms-GlueTransform.md#aws-glue-api-crawler-pyspark-transforms-GlueTransform-name).

## describeArgs(cls)
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-describeArgs"></a>

Inherited from `GlueTransform` [describeArgs](aws-glue-api-crawler-pyspark-transforms-GlueTransform.md#aws-glue-api-crawler-pyspark-transforms-GlueTransform-describeArgs).

## describeReturn(cls)
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-describeReturn"></a>

Inherited from `GlueTransform` [describeReturn](aws-glue-api-crawler-pyspark-transforms-GlueTransform.md#aws-glue-api-crawler-pyspark-transforms-GlueTransform-describeReturn).

## describeTransform(cls)
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-describeTransform"></a>

Inherited from `GlueTransform` [describeTransform](aws-glue-api-crawler-pyspark-transforms-GlueTransform.md#aws-glue-api-crawler-pyspark-transforms-GlueTransform-describeTransform).

## describeErrors(cls)
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-describeErrors"></a>

Inherited from `GlueTransform` [describeErrors](aws-glue-api-crawler-pyspark-transforms-GlueTransform.md#aws-glue-api-crawler-pyspark-transforms-GlueTransform-describeErrors).

## describe(cls)
<a name="aws-glue-api-crawler-pyspark-transforms-flat-map-describe"></a>

Inherited from `GlueTransform` [describe](aws-glue-api-crawler-pyspark-transforms-GlueTransform.md#aws-glue-api-crawler-pyspark-transforms-GlueTransform-describe).