- /?hnlog pycontract icontract https://westurner.github.io/hnlog/ :

From https://news.ycombinator.com/item?id=14246095 (2017) :

> PyContracts supports runtime type-checking and value constraints/assertions (as @contract decorators, annotations, and docstrings).

> Unfortunately, there's yet no unifying syntax between PyContracts and the newer python type annotations which MyPy checks at compile-type.

Or beartype.

Pycontracts has: https://andreacensi.github.io/contracts/ :

  @contract
  def my_function(a : 'int,>0', b : 'list[N],N>0') -> 'list[N]':
  
  @contract(image='array[HxWx3](uint8),H>10,W>10')
  def recolor(image):

parquery/icontract: https://github.com/Parquery/icontract :

> There exist a couple of contract libraries. However, at the time of this writing (September 2018), they all required the programmer either to learn a new syntax (PyContracts) or to write redundant condition descriptions ( e.g., contracts, covenant, deal, dpcontracts, pyadbc and pcd).

  @icontract.require(lambda x: x > 3, "x must not be small")
  def some_func(x: int, y: int = 5) -> None:

  @icontract.require(lambda arr: isinstance(arr, np.ndarray))
  @icontract.require(lambda arr: arr.shape == (3, 3))
  @icontract.require(lambda arr: np.all(arr >= 0), "All elements must be non-negative")
  def process_matrix(arr: np.ndarray):
      return np.sum(arr)

  invalid_matrix = np.array([[1, -2, 3], [4, 5, 6], [7, 8, 9]])
  process_matrix(invalid_matrix)
  # Raises icontract.ViolationError