mock_alchemy.utils

A module for utils for the mock-alchemy library.

mock_alchemy.utils.build_identity_map(items)

Builds identity map.

Utility for building identity map from given SQLAlchemy models.

Parameters

items (Sequence[Any]) – A sequence of SQLAlchemy objects.

Return type

Dict

Returns

An identity map of the given SQLAlchemy objects.

For example:

>>> from sqlalchemy import Column, Integer, String
>>> from sqlalchemy.ext.declarative import declarative_base

>>> Base = declarative_base()

>>> class SomeClass(Base):
...     __tablename__ = 'some_table'
...     pk1 = Column(Integer, primary_key=True)
...     pk2 = Column(Integer, primary_key=True)
...     name =  Column(String(50))
...     def __repr__(self):
...         return str(self.pk1)

>>> build_identity_map([SomeClass(pk1=1, pk2=2)])
{(1, 2): 1}

mock_alchemy.utils.copy_and_update(target, updater)

Copy and update dictionary.

Copy dictionary and update it all in one operation.

Parameters

• target (Dict) – The dictionary to copy and update.

• updater (Dict) – The updating dictionary.

Returns

A new dictionary of the target copied and updated by updater.

Return type

Dict

For example:

>>> a = {'foo': 'bar'}
>>> b = copy_and_update(a, {1: 2})
>>> a is b
False
>>> b == {'foo': 'bar', 1: 2}
True

mock_alchemy.utils.get_item_attr(idmap, access)

Access dictionary in different methods.

Utility for accessing dict by different key types (for get).

Parameters

• idmap (Dict) – A dictionary of identity map of SQLAlchemy objects.

• access (Union[Dict, Tuple, int]) – The access pattern which should either be int, dictionary, or a tuple. If it is dictionary it should map to the names of the primary keys of the SQLAlchemy objects. If it is a tuple, it should be a set of keys to search for. If it is an int, then the objects in question must have only one primary key.

Return type

Any

Returns

An SQlAlchemy object that was requested.

For example::

>>> idmap = {(1,): 2}
>>> get_item_attr(idmap, 1)
2
>>> idmap = {(1,): 2}
>>> get_item_attr(idmap, {"pk": 1})
2
>>> get_item_attr(idmap, (1,))
2

mock_alchemy.utils.indexof(needle, haystack)

Gets the index of some item in a sequence.

Find an index of needle in haystack by looking for exact same item by pointer ids vs usual list.index() which finds by object comparison.

Parameters

• needle (Any) – The object or item to find in the sequence.

• haystack (Sequence[Any]) – The sequence of items to search for the needle.

Return type

int

Returns

The index of the needle in the haystack.

Raises

ValueError – If the needle is not found inside the haystack.

For example:

>>> a = {}
>>> b = {}
>>> haystack = [1, a, 2, b]
>>> indexof(b, haystack)
3
>>> indexof(None, haystack)
Traceback (most recent call last):
...
ValueError: None is not in [1, {}, 2, {}]

mock_alchemy.utils.match_type(s, t)

Match the string type.

Matches the string type with the provided type and returns the string of the desired type.

Parameters

• s (Union[bytes, str]) – The string to match the type with.

• t (Union[Type[bytes], Type[str]]) – The type to make the string with.

Return type

Union[bytes, str]

Returns

An object of the desired type of type t.

For example:

>>> assert type(match_type(b'hello', bytes)) is bytes
>>> assert type(match_type(u'hello', str)) is str
>>> assert type(match_type(b'hello', str)) is str
>>> assert type(match_type(u'hello', bytes)) is bytes

mock_alchemy.utils.raiser(exp, *args, **kwargs)

Raises an exception with the given args.

Utility for raising exceptions Useful in one-liners.

Parameters

• exp (Type[Exception]) – The exception to raise.

• args (Any) – The args to use for the exception.

• kwargs (Any) – The kwargs to use for the exception.

Raises

exp – The parameterized exception of the specified kind.

For example:

>>> a = lambda x: not x and raiser(ValueError, 'error message')
>>> _ = a(True)
>>> _ = a(False)
Traceback (most recent call last):
...
ValueError: error message

Return type

Type[Exception]

mock_alchemy.utils.setattr_tmp(obj, name, value)

Set the atrributes of object temporarily.

Utility for temporarily setting value in an object.

Parameters

• obj (object) – An object to set the attribute of.

• name (str) – The name of the attribute.

• value (Any) – The value to set the attribute to.

Return type

Any

Returns

A context manager that can be used.

Yields

Used for the context manager so that this function can be used as with setattr_tmp.

For example:

>>> class Foo(object):
...     foo = 'foo'
>>> print(Foo.foo)
foo
>>> with setattr_tmp(Foo, 'foo', 'bar'):
...     print(Foo.foo)
bar
>>> print(Foo.foo)
foo

>>> Foo.foo = None
>>> with setattr_tmp(Foo, 'foo', 'bar'):
...     print(Foo.foo)
None