https://github.com/pynamodb/pynamodb-mypy

mypy plugin for PynamoDB
https://github.com/pynamodb/pynamodb-mypy

Last synced: about 2 months ago
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mypy plugin for PynamoDB

• Host: GitHub
• URL: https://github.com/pynamodb/pynamodb-mypy
• Owner: pynamodb
• License: apache-2.0
• Created: 2020-05-18T14:35:11.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2022-10-21T03:25:10.000Z (almost 2 years ago)
• Last Synced: 2024-07-05T13:53:01.169Z (3 months ago)
• Language: Python
• Homepage:
• Size: 41 KB
• Stars: 4
• Watchers: 2
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-python-typing - pynamodb-mypy - Plugin for [PynamoDB](https://github.com/pynamodb/PynamoDB) support. (Tools / Mypy plugins)

README

        
# 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:

```ini

[mypy]

plugins = pynamodb_mypy

```

# Nullable attributes

When declaring attributes with `null=True`, the value types would become optional. For example:

```py

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.:

```py

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:

```py

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"

```