Adding type-hinting to functions that return boto3 objects?

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How do I add type-hinting to my functions that return various boto3 resources? I'd like to get automatic completion/checking on my return values in IDEs like PyCharm. Boto3 does some factory creation magic so I can't figure out how to declare the types correctly

import boto3 ec2 = boto3.Session().resource('ec2') a = ec2.Image('asdf') a.__class__ # => boto3.resources.factory.ec2.Image

But boto3.resources.factory.ec2.Image doesn't seem to be a class that's recognized by Python. So I can't use it for a type hint.

The docs show that the return type is EC2.Image. But is there a way to import that type as regular Python type?

boto3 amazon-web-services python-3.x
2 Answers

UPDATE 2021

As mentioned by @eega, I no longer maintain the package. I'd recommend checking out boto3-stubs. It's a much more mature version of boto3_type_annotations.

Original Answer

I made a package that can help with this, boto3_type_annotations. It's available with or without documentation as well. Example usage below. There's also a gif at my github showing it in action using PyCharm.

import boto3
from boto3_type_annotations.s3 import Client, ServiceResource
from boto3_type_annotations.s3.waiter import BucketExists
from boto3_type_annotations.s3.paginator import ListObjectsV2

# With type annotations

client: Client = boto3.client('s3')
client.create_bucket(Bucket='foo')  # Not only does your IDE knows the name of this method, 
                                    # it knows the type of the `Bucket` argument too!
                                    # It also, knows that `Bucket` is required, but `ACL` isn't!

# Waiters and paginators and defined also...

waiter: BucketExists = client.get_waiter('bucket_exists')
waiter.wait('foo')

paginator: ListObjectsV2 = client.get_paginator('list_objects_v2')
response = paginator.paginate(Bucket='foo')

# Along with service resources.

resource: ServiceResource = boto3.resource('s3')
bucket = resource.Bucket('bar')
bucket.create()

# With type comments

client = boto3.client('s3')  # type: Client
response = client.get_object(Bucket='foo', Key='bar')


# In docstrings

class Foo:
    def __init__(self, client):
        """
        :param client: It's an S3 Client and the IDE is gonna know what it is!
        :type client: Client
        """
        self.client = client

    def bar(self):
        """
        :rtype: Client
        """
        self.client.delete_object(Bucket='foo', Key='bar')
        return self.client
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