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Exception factory

Project description

# python-should-check

Check parameters and raise comprehensible exceptions.

>>> from should_check import (
...    Check,
...    be_callable,
...    be_py_enum_str,
...    be_instance_of,
...    be_subclass_of,
...    not_be_none,
...    not_contain,
...    contain,
...    not_be_empty,
...    be_shorter_than,
...    be_length_of,
...    not_be_negative,
...    be_greater_than,
...    be_less_than,
...    be_equal_with,
...    be,
...    be_in)

## Check if a function is a callable and not None

>>> function = Check(function=print).should(not_be_none, be_callable)
>>> function("Hello world")
Hello world
>>> function = Check(function=None).should(not_be_none, be_callable)
Traceback (most recent call last):
...
ValueError: 'function' should not be None
>>> function = Check(function="boo").should(not_be_none, be_callable)
Traceback (most recent call last):
...
ValueError: 'function' should be callable

If the ‘None’ would not go through some of these checks, it would be cumbersome to check optional parameters on your functions. This for example works:

>>> function = Check(function=None).should(be_callable)

But these wont:

>>> checked = Check(value=None).should(be(1))
Traceback (most recent call last):
...
ValueError: value 'None' should (reference equally) be '1'
>>> checked = Check(value=None).should(be_in([1,2]))
Traceback (most recent call last):
...
ValueError: value 'None' should be in '[1, 2]'
>>> checked = Check(value=None).should(be_equal_with(1))
Traceback (most recent call last):
...
ValueError: value 'None' should be equal with '1'

So be carefull with None and add the check everywhere like you should anyway.

## Check if a string is a member of an enum definition

>>> import enum
>>> class MyEnum(enum.IntEnum):
...   GOOD_ENUM = 0
...   MEH_ENUM = 1
...
>>> enum_str = Check(enum_str="GOOD_ENUM").should(not_be_none, be_py_enum_str(MyEnum))
>>> enum_str = Check(enum_str="BAD_ENUM").should(not_be_none, be_py_enum_str(MyEnum))
Traceback (most recent call last):
...
TypeError: enum_str 'BAD_ENUM' should be one of '['GOOD_ENUM', 'MEH_ENUM']'

## Check if an object is an instance of a class

>>> my_enum = MyEnum(0)
>>> second_enum = Check(my_enum=my_enum).should(not_be_none, be_instance_of(MyEnum))
>>> second_enum =  Check(my_enum=my_enum).should(not_be_none, be_instance_of(int))
>>> second_enum =  Check(my_enum=my_enum).should(not_be_none, be_instance_of(str))
Traceback (most recent call last):
...
TypeError: my_enum '0' should be instance of '<class 'str'>'

## Check if a class is a subclass another

>>> CheckedClass = Check(subclass=MyEnum).should(
...    not_be_none,
...    be_subclass_of(enum.IntEnum),
...    be_subclass_of(int),
...    be_subclass_of(str))
Traceback (most recent call last):
...
TypeError: subclass '<enum 'MyEnum'>' should be subclass of '<class 'str'>'

## Check that an item is not in container

>>> checked_item = Check(item=[1,2,3]).should(not_be_none, not_contain(51))
>>> checked_item = Check(item=[1,2,3]).should(not_be_none, not_contain(1))
Traceback (most recent call last):
...
ValueError: 'item' should not contain '1'

## Check that an item is in a container

>>> checked_item = Check(item=[1,2,3]).should(not_be_none, contain(1))
>>> checked_item = Check(item=[1,2,3]).should(not_be_none, contain(51))
Traceback (most recent call last):
...
ValueError: 'item' should contain '51'

## Check that a collection is not empty

>>> not_empty = Check(collection=[1,2,3]).should(not_be_none, not_be_empty)
>>> not_empty = Check(collection=set()).should(not_be_none, not_be_empty)
Traceback (most recent call last):
...
ValueError: 'collection' should not be empty

## Length checks for containers (strings)

>>> capped = Check(number="a").should(not_be_none, be_shorter_than(2))
>>> capped = Check(number="aaa").should(not_be_none, be_shorter_than(2))
Traceback (most recent call last):
...
ValueError: number length '3' should be equal or less than '2'
>>> fixed = Check(number="aa").should(not_be_none, be_length_of(2))
>>> fixed = Check(number="aaa").should(not_be_none, be_length_of(2))
Traceback (most recent call last):
...
ValueError: number length '3' should be equal with '2'

## Range checks for numbers:

>>> positive = Check(number=-1).should(not_be_none, not_be_negative)
Traceback (most recent call last):
...
ValueError: 'number' should not be negative
>>> positive = Check(number=-1).should(not_be_none, be_greater_than(0))
Traceback (most recent call last):
...
ValueError: number '-1' should be greater than '0'
>>> positive = Check(number=4).should(not_be_none, be_less_than(1))
Traceback (most recent call last):
...
ValueError: number '4' should be less than '1'

## Equality checks

>>> equals_one = Check(number="1").should(not_be_none, be_equal_with("1"))
>>> equals_one = Check(number="2").should(not_be_none, be_equal_with("1"))
Traceback (most recent call last):
...
ValueError: number '2' should be equal with '1'
>>> reference = object()
>>> equals_one = Check(object=reference).should(not_be_none, be(reference))
>>> equals_one = Check(object="another").should(be(None))
Traceback (most recent call last):
...
ValueError: object 'another' should (reference equally) be 'None'

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