预告
我们在这里提供了一些预告来激励这个库。有关其完整功能的详细信息，请参阅icontract.readthedocs.io上的文档。
脚本也可以在repl.it帖子中找到。
>>> import icontract
>>> @icontract.require(lambda x: x > 3)
... def some_func(x: int, y: int = 5) -> None:
... pass
...
>>> some_func(x=5)
# Pre-condition violation
>>> some_func(x=1)
Traceback (most recent call last):
...
icontract.errors.ViolationError: File <doctest README.rst[1]>, line 1 in <module>:
x > 3:
x was 1
y was 5
# Pre-condition violation with a description
>>> @icontract.require(lambda x: x > 3, "x must not be small")
... def some_func(x: int, y: int = 5) -> None:
... pass
...
>>> some_func(x=1)
Traceback (most recent call last):
...
icontract.errors.ViolationError: File <doctest README.rst[4]>, line 1 in <module>:
x must not be small: x > 3:
x was 1
y was 5
# Pre-condition violation with more complex values
>>> class B:
... def __init__(self) -> None:
... self.x = 7
...
... def y(self) -> int:
... return 2
...
... def __repr__(self) -> str:
... return "instance of B"
...
>>> class A:
... def __init__(self) -> None:
... self.b = B()
...
... def __repr__(self) -> str:
... return "instance of A"
...
>>> SOME_GLOBAL_VAR = 13
>>> @icontract.require(lambda a: a.b.x + a.b.y() > SOME_GLOBAL_VAR)
... def some_func(a: A) -> None:
... pass
...
>>> an_a = A()
>>> some_func(an_a)
Traceback (most recent call last):
...
icontract.errors.ViolationError: File <doctest README.rst[9]>, line 1 in <module>:
a.b.x + a.b.y() > SOME_GLOBAL_VAR:
SOME_GLOBAL_VAR was 13
a was instance of A
a.b was instance of B
a.b.x was 7
a.b.y() was 2
# Post-condition
>>> @icontract.ensure(lambda result, x: result > x)
... def some_func(x: int, y: int = 5) -> int:
... return x - y
...
>>> some_func(x=10)
Traceback (most recent call last):
...
icontract.errors.ViolationError: File <doctest README.rst[12]>, line 1 in <module>:
result > x:
result was 5
x was 10
y was 5
# Pre-conditions fail before post-conditions.
>>> @icontract.ensure(lambda result, x: result > x)
... @icontract.require(lambda x: x > 3, "x must not be small")
... def some_func(x: int, y: int = 5) -> int:
... return x - y
...
>>> some_func(x=3)
Traceback (most recent call last):
...
icontract.errors.ViolationError: File <doctest README.rst[14]>, line 2 in <module>:
x must not be small: x > 3:
x was 3
y was 5
# Invariant
>>> @icontract.invariant(lambda self: self.x > 0)
... class SomeClass:
... def __init__(self) -> None:
... self.x = -1
...
... def __repr__(self) -> str:
... return "an instance of SomeClass"
...
>>> some_instance = SomeClass()
Traceback (most recent call last):
...
icontract.errors.ViolationError: File <doctest README.rst[16]>, line 1 in <module>:
self.x > 0:
self was an instance of SomeClass
self.x was -1
