pynamodb-mypy 0.1.2

Description:

pynamodbmypy 0.1.2

pynamodb-mypy
A plugin for mypy which gives it deeper understanding of PynamoDB (beyond what's possible through type stubs).
Usage
Add it to the plugins option of the [mypy] section in your mypy.ini:
[mypy]
plugins = pynamodb_mypy

Nullable attributes
When declaring attributes with null=True, the value types would become optional. For example:
from pynamodb.attributes import UnicodeAttribute
from pynamodb.models import Model

class MyModel(Model):
my_key = UnicodeAttribute()
my_value = UnicodeAttribute(null=True)

...
my_model = MyModel.get('key')
if my_model.my_value.lower() == 'foo': # error: Item "None" of "Optional[str]" has no attribute "lower"
print("Value is foo")

would have to be changed to, e.g.:
if my_model.my_value and my_model.my_value.lower() == 'foo':
print("Value is foo")

Typed model initializers
When declaring models, the __init__ method would be typed to accept only the attributes declared in the model. For example:
from pynamodb.models import Model
from pynamodb.attributes import NumberAttribute
from pynamodb.attributes import UnicodeAttribute

class MyModel(Model):
my_key = UnicodeAttribute(hash_key=True)
my_value = NumberAttribute(null=True)

# Existing attributes would be enforced:
_ = MyModel(my_key='key', my_value=42, my_other_value='other_value') # error: Unexpected keyword argument "my_other_value" for "MyModel"

# Typing would be enforced:
_ = MyModel(my_key='key', my_value='42') # error: Argument 2 to "MyModel" has incompatible type "str"; expected "Optional[int]"

# Nullability will be enforced::
_ = MyModel(my_key='key', my_value=None)
_ = MyModel(my_key=None, my_value=None) # error: Argument "my_key" to "MyModel" has incompatible type "None"; expected "str"

# The hash key and range key can also be passed as positional arguments:
_ = MyModel('key')
_ = MyModel(42) # error: Argument 1 to "MyModel" has incompatible type "int"; expected "str"