A plugin for mypy which gives it deeper understanding of PynamoDB (beyond what's possible through type stubs).
Add it to theplugins option of the[mypy] section in your mypy.ini:
[mypy]plugins = pynamodb_mypy
When declaring attributes withnull=True, the value types would become optional. For example:
frompynamodb.attributesimportUnicodeAttributefrompynamodb.modelsimportModelclassMyModel(Model):my_key=UnicodeAttribute()my_value=UnicodeAttribute(null=True)...my_model=MyModel.get('key')ifmy_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.:
ifmy_model.my_valueandmy_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:
frompynamodb.modelsimportModelfrompynamodb.attributesimportNumberAttributefrompynamodb.attributesimportUnicodeAttributeclassMyModel(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"