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Type annotations for boto3. Adds code completion in IDEs such as PyCharm.

Project description


A programmatically created package that defines boto3 services as stand in classes with type annotations. boto3 is an incredibly useful, well designed interface to the AWS API. However, we live in an age where even free IDEs like PyCharm CE have full code completion (IntelliSense). Because boto3's services are created at runtime, IDEs aren't able to index its code in order to provide code completion or infer the type of these services or of the objects created by them. Even if it was able to do so, clients and service resources are created using a service agnostic factory method and are only identified by a string argument of that method. IDEs don't parse arguments to infer the return type of a method, and they probably shouldn't. Meaning that the only way for an IDE to know the type of a client created by boto3.client('<service>') is for it to be explicitly declared in type annotations, type comments, or docstrings, which brings us back to the original problem of services being defined at runtime. All of that to say that working with boto3 can be very frustrating at times.

To reduce this frustration, boto3_type_annotations defines stand in classes for the clients, service resources, paginators, and waiters provided by boto3's services. Even though these services are created by boto3 are created at runtime, they are still full fledged Python objects, and AWS has been nice enough to include documentation in the docstrings of these objects' methods. By parsing those docstrings, we can retrieve the types of method arguments--also, which arguments are required and which may be omitted--and the types of their return values. With that, we have everything we need to create objects which mimic the class structure of boto3's objects. And with Python's typing module, we can annotate the methods of the stand in objects with the types which we've parsed. What this means is that we can use these stand in objects to declare the type of boto3 service objects in our own code.


With or Without Docstrings

This package is available both with docstrings, named boto3_type_annotations_with_docs on PyPi (which contains the same documentation you'll find online), and without, named boto3_type_annotations on PyPi. The reason for this is that, for a python package, boto3_type_annotations_with_docs is HUGE. boto3_type_annotations is pretty large itself at 2.2 MB, but boto3_type_annotations_with_docs dwarfs it at 41 MB. Being that boto3 and botocore add up to be 34 MB, this is likely not ideal for many use cases. However, there are use cases in which you may want documentation in your IDE, during development for example. A possible workflow for this use case is detailed below.


Without docs:

pip install boto3_type_annotations

With docs:

pip install boto3_type_annotations_with_docs


Regardless of which deployment package you install, you'll still import the same package, boto3_type_annotations. Its constituent packages and modules can be used to declare the type of boto3 objects. For instance, everybody's favorite, S3:

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')

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')

# 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

How Is This Package Different From pyboto3?

pyboto3 has been a useful package which was created for the same purpose and using the same methodology as this package. It does have its shortcomings, though. For one, it only defines clients, no service resources, waiters, or paginators. Two, it defines2 clients as modules when the objects created by boto3 are classes. This seems nitpicky until you realize that modules can't be used to declare type with type annotations. Even a variable in the outermost scope of a module would require rst docstring to declare its type. Also, and this is actually is nitpicky, the package structure doesn't mimic that of boto3--which you can see in the documentation i.e. sqs.ServiceResource, s3.Bucket, ec2.waiter.InstanceExists. Though I don't want to purport that this is perfectly one to one with what is in the docs. For instance, there's not much consistency in the docs as far as casing. You'll sometimes see S3.Waiter.BucketExists and in other places sqs.Bucket. I chose to go with the pep8 guidelines where module names are in snake case and classes are in Pascal case.

Development Workflow With Docstring

As mentioned above, there may be scenarios in which you would want to have docstrings in development, but not want to package a 41MB dependency with your production code. To accommodate this and similar scenarios, I decided to provide two deployment packages, each containing a boto3_type_annotations package. So, one workflow may be to have two requirements files: requirements.txt and requirements-dev.txt (boto3 does something similar in that they have requirements.txt for the API resource and requirements-docs.txt for building documentation.). These two files would look like this:


# other dependencies


# other dependencies

You would then install requirements.txt in production and requirements-dev.txt in development. Because both deployment packages define the boto3_type_annotations package, you won't have to change your code. You just need to install the appropriate deployment package.

Custom Builds

In cases when you're only using a small number of boto3 services, you may not want to depend on a package containing every service available. To provide a bit more flexibility, this package provides a way to create a custom build of the boto3_type_annotations package. The configs/ directory contains configurations for boto3_type_annotations and boto3_type_annnotations_with_docs, along with a couple example configurations.

services: # A list of services. Use `boto3.session.Session.get_available_services()` to view services. 
  - ec2
  - rds
  - sqs
  - sns
  - lambda
  - s3
with_docs: true # Include docstrings.
with_clients: true # Include client classes
with_service_resources: true # Include service resources.
with_paginators: true # Include paginators
with_waiters: true # Include waiters
package_name: boto3_type_annotations_essentials # The name of the package.
module_name: boto3_type_annotations # The name of the module.
version: 0.2.4 # Version of the package.
readme: # Path to readme file.
license: LICENSE # Path to file containing license.

The preceding configuration is the contents of config/example.essentials.yaml. When is run with this config, it will parse and write the ec2, rds, sqs, sns, lambda, and s3 services with docstrings and including all clients, service resources, paginators, and waiters.

$ python build_scripts/ ../configs/example.essentials.yaml

It will create a directory named boto3_type_annotations_essentials in the root directory of the repository. That directory will contain a python module named boto3_type_annotations, a license file, and a file. Now all you need to do is package everything up and install it.

$ python sdist bdist_wheel

$ pip3 install dist/boto3_type_annotations_essentials-0.2.4-py3-none-any.whl --user


  • Create an "essentials" deployment package only containing often used services like Lambda, S3, SQS, and CloudFormation

  • Package related services into separate deployment packages, to create smaller packages containing only services which are essential to a certain use case, group EC2 and RDS for instance.

  • Create custom builds. If a project only uses S3's service resource, provide a way to build a deployment package containing just that package. This would require some sort of configuration and more mature build script.

  • Reduce the size of boto3_type_annotations_with_docs. I'm already cutting out extraneous new lines and some whitespaces which reduced the size by 10 MB(!), but I'd like to see it closer to the 34 MB of boto3 + botocore.

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