title: sqlalchemy.orm.attributes InstrumentedAttribute Example Code category: page slug: sqlalchemy-orm-attributes-instrumentedattribute-examples sortorder: 500031076 toc: False sidebartitle: sqlalchemy.orm.attributes InstrumentedAttribute meta: Example code for understanding how to use the InstrumentedAttribute class from the sqlalchemy.orm.attributes module of the SQLAlchemy project.
InstrumentedAttribute is a class within the sqlalchemy.orm.attributes module of the SQLAlchemy project.
QueryableAttribute
and
flag_modified
are a couple of other callables within the sqlalchemy.orm.attributes package that also have code examples.
SQLAlchemy Mixins (PyPI package information) is a collection of mixins useful for extending SQLAlchemy and simplifying your database-interacting code for some common use cases. SQLAlchemy Mixins is open sourced under the MIT license.
SQLAlchemy Mixins / sqlalchemy_mixins / eagerload.py
# eagerload.py
try:
from typing import List
except ImportError: # pragma: no cover
pass
from sqlalchemy.orm import joinedload
from sqlalchemy.orm import subqueryload
~~from sqlalchemy.orm.attributes import InstrumentedAttribute
from .session import SessionMixin
JOINED = 'joined'
SUBQUERY = 'subquery'
def eager_expr(schema):
flat_schema = _flatten_schema(schema)
return _eager_expr_from_flat_schema(flat_schema)
def _flatten_schema(schema):
def _flatten(schema, parent_path, result):
for path, value in schema.items():
~~ if isinstance(path, InstrumentedAttribute):
path = path.key
if isinstance(value, tuple):
join_method, inner_schema = value[0], value[1]
elif isinstance(value, dict):
join_method, inner_schema = JOINED, value
else:
join_method, inner_schema = value, None
full_path = parent_path + '.' + path if parent_path else path
result[full_path] = join_method
if inner_schema:
_flatten(inner_schema, full_path, result)
result = {}
_flatten(schema, '', result)
return result
def _eager_expr_from_flat_schema(flat_schema):
result = []
for path, join_method in flat_schema.items():
if join_method == JOINED:
## ... source file continues with no further InstrumentedAttribute examples...sqlalchemy-utils (project documentation and PyPI package information) is a code library with various helper functions and new data types that make it easier to use SQLAlchemy when building projects that involve more specific storage requirements such as currency. The wide array of data types includes ranged values and aggregated attributes.
sqlalchemy-utils / sqlalchemy_utils / path.py
# path.py
import sqlalchemy as sa
~~from sqlalchemy.orm.attributes import InstrumentedAttribute
from sqlalchemy.util.langhelpers import symbol
from .utils import str_coercible
@str_coercible
class Path(object):
def __init__(self, path, separator='.'):
if isinstance(path, Path):
self.path = path.path
else:
self.path = path
self.separator = separator
@property
def parts(self):
return self.path.split(self.separator)
def __iter__(self):
for part in self.parts:
yield part
def __len__(self):
return len(self.parts)
## ... source file abbreviated to get to InstrumentedAttribute examples ...
return "%s('%s')" % (self.__class__.__name__, self.path)
def index(self, element):
return self.parts.index(element)
def __getitem__(self, slice):
result = self.parts[slice]
if isinstance(result, list):
return self.__class__(
self.separator.join(result),
separator=self.separator
)
return result
def __eq__(self, other):
return self.path == other.path and self.separator == other.separator
def __ne__(self, other):
return not (self == other)
def __unicode__(self):
return self.path
def get_attr(mixed, attr):
~~ if isinstance(mixed, InstrumentedAttribute):
return getattr(
mixed.property.mapper.class_,
attr
)
else:
return getattr(mixed, attr)
@str_coercible
class AttrPath(object):
def __init__(self, class_, path):
self.class_ = class_
self.path = Path(path)
self.parts = []
last_attr = class_
for value in self.path:
last_attr = get_attr(last_attr, value)
self.parts.append(last_attr)
def __iter__(self):
for part in self.parts:
yield part
def __invert__(self):
## ... source file continues with no further InstrumentedAttribute examples...wtforms-alchemy (documentation and PyPI package information) is a WTForms extension toolkit for easier creation of SQLAlchemy model based forms. While this project primarily focuses on proper form handling, it also has many good examples of how to use various parts of SQLAlchemy in its code base. The project is provided as open source under the MIT license.
WTForms-Alchemy / wtforms_alchemy / validators.py
# validators.py
from collections.abc import Iterable, Mapping
import six
from sqlalchemy import Column
~~from sqlalchemy.orm.attributes import InstrumentedAttribute
from wtforms import ValidationError
class Unique(object):
field_flags = ('unique', )
def __init__(self, column, get_session=None, message=None):
self.column = column
self.message = message
self.get_session = get_session
@property
def query(self):
self._check_for_session(self.model)
if self.get_session:
return self.get_session().query(self.model)
elif hasattr(self.model, 'query'):
return getattr(self.model, 'query')
else:
raise Exception(
'Validator requires either get_session or Flask-SQLAlchemy'
' styled query parameter'
)
## ... source file continues with no further InstrumentedAttribute examples...