Programming by contract library.
Project description
Pre (pre, require):
In [1]: from deal import pre, post, inv
In [2]: @pre(lambda *args: all(map(lambda x: x > 0, args)))
...: def my_sum(*args):
...: return sum(args)
...:
In [3]: my_sum(2, 3, 4)
Out[3]: 9
In [4]: my_sum(2, -3, 4)
PreContractError:Post (post, ensure):
In [5]: @post(lambda x: x > 0)
...: def my_sum(*args):
...: return sum(args)
...:
In [6]: my_sum(2, -3, 4)
Out[6]: 3
In [7]: my_sum(2, -3, -4)
PostContractError:Inv (inv, invariant):
In [8]: @inv(lambda obj: obj.x > 0)
...: class A:
...: x = 4
...:
In [9]: a = A()
In [10]: a.x = 10
In [11]: a.x = -10
InvContractError:
In [12]: A
Out[12]: contracts.core.AInvariantedCustom message:
In [13]: @pre(lambda x: x > 0, "x must be > 0")
...: def f(x):
...: return x * 2
...:
In [14]: f(-2)
PreContractError: x must be > 0Custom exception:
In [15]: @pre(lambda x: x > 0, exception=AssertionError("x must be > 0"))
...: def f(x):
...: return x * 2
...:
In [16]: f(-2)
AssertionError: x must be > 0Validators (nearly Django Forms style, except initialization):
In [19]: class Validator:
...: def __init__(self, x):
...: self.x = x
...:
...: def is_valid(self):
...: if self.x <= 0:
...: self.errors = ['x must be > 0']
...: return False
...: return True
...:
In [20]: @pre(Validator)
...: def f(x):
...: return x * 2
...:
In [21]: f(5)
Out[21]: 10
In [22]: f(-5)
PreContractError: ['x must be > 0']Return error message from contract:
In [23]: @pre(lambda x: x > 0 or "x must be > 0")
...: def f(x):
...: return x * 2
...:
In [24]: f(-5)
PreContractError: x must be > 0Release history Release notifications | RSS feed
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