Python relative imports in AWS Lambda fail with `attempted relative import with no known parent package`

# The Problem

In AWS Lambda if I attempt an explicit relative import like this

```
.
├── lambda_file.py
└── example.py
```

```
# lambda_file.py
from .example import lambda_handler
```

```
# example.py
def lambda_handler(event, context):
    return True
```

And I configure AWS Lambda's handler to `lambda_file.lambda_handler` I get the following errors

* Python 2.7 : `Attempted relative import in non-package`
* Python 3.7 : `attempted relative import with no known parent package`

# Why use explicit relative imports

[PEP008](https://www.python.org/dev/peps/pep-0008/#id23) says :

> Implicit relative imports should never be used and have been removed in Python 3.

# How to workaround by using implicit relative imports

If I change `lambda_file.py` to contain the following, it works, but no longer uses explicit relative imports

```
# lambda_file.py
from example import lambda_handler
```

# How to correctly solve the problem

The solution is to ensure that the "Handler" value that you configure in AWS Lambda contain at least 2 `.` periods. To achieve this you need to put your code within a directory in your AWS Lambda code zip file and make that directory a module by adding an empty `__init__.py` file. The resulting structure looks like this


```
.
├── app
│   ├── __init__.py
│   ├── lambda_file.py
│   └── example.py

```

And you now change the "Handler" value from `lambda_file.lambda_handler` to `app.lambda_file.lambda_handler`

# Additional Notes

* AWS Lambda [loads your handler as a module import](https://docs.aws.amazon.com/lambda/latest/dg/lambda-python.html) not as a top-level script
* This solution came after reading [this explanation of explicit relative imports](https://stackoverflow.com/a/14132912/168874) by [Brendan Barnwell](https://stackoverflow.com/users/1427416/brenbarn)