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