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281 lines
11 KiB
Plaintext
Metadata-Version: 2.1
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Name: traitlets
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Version: 5.8.0
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Summary: Traitlets Python configuration system
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Project-URL: Homepage, https://github.com/ipython/traitlets
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Author-email: IPython Development Team <ipython-dev@python.org>
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License: # Licensing terms
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Traitlets is adapted from enthought.traits, Copyright (c) Enthought, Inc.,
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under the terms of the Modified BSD License.
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This project is licensed under the terms of the Modified BSD License
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(also known as New or Revised or 3-Clause BSD), as follows:
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- Copyright (c) 2001-, IPython Development Team
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer.
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Redistributions in binary form must reproduce the above copyright notice, this
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list of conditions and the following disclaimer in the documentation and/or
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other materials provided with the distribution.
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Neither the name of the IPython Development Team nor the names of its
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contributors may be used to endorse or promote products derived from this
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software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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## About the IPython Development Team
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The IPython Development Team is the set of all contributors to the IPython project.
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This includes all of the IPython subprojects.
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The core team that coordinates development on GitHub can be found here:
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https://github.com/jupyter/.
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## Our Copyright Policy
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IPython uses a shared copyright model. Each contributor maintains copyright
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over their contributions to IPython. But, it is important to note that these
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contributions are typically only changes to the repositories. Thus, the IPython
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source code, in its entirety is not the copyright of any single person or
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institution. Instead, it is the collective copyright of the entire IPython
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Development Team. If individual contributors want to maintain a record of what
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changes/contributions they have specific copyright on, they should indicate
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their copyright in the commit message of the change, when they commit the
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change to one of the IPython repositories.
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With this in mind, the following banner should be used in any source code file
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to indicate the copyright and license terms:
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```
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# Copyright (c) IPython Development Team.
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# Distributed under the terms of the Modified BSD License.
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```
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License-File: COPYING.md
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Keywords: Interactive,Interpreter,Shell,Web
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Classifier: Intended Audience :: Developers
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Classifier: Intended Audience :: Science/Research
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Classifier: Intended Audience :: System Administrators
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Classifier: License :: OSI Approved :: BSD License
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Classifier: Programming Language :: Python
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Classifier: Programming Language :: Python :: 3
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Requires-Python: >=3.7
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Provides-Extra: docs
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Requires-Dist: myst-parser; extra == 'docs'
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Requires-Dist: pydata-sphinx-theme; extra == 'docs'
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Requires-Dist: sphinx; extra == 'docs'
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Provides-Extra: test
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Requires-Dist: argcomplete>=2.0; extra == 'test'
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Requires-Dist: pre-commit; extra == 'test'
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Requires-Dist: pytest; extra == 'test'
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Requires-Dist: pytest-mock; extra == 'test'
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Description-Content-Type: text/markdown
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# Traitlets
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[](https://github.com/ipython/traitlets/actions/workflows/tests.yml)
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[](https://traitlets.readthedocs.io/en/latest/?badge=latest)
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[](https://codecov.io/gh/ipython/traitlets)
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[](https://tidelift.com/badges/package/pypi/traitlets)
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| | |
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| ------------- | ------------------------------------ |
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| **home** | https://github.com/ipython/traitlets |
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| **pypi-repo** | https://pypi.org/project/traitlets/ |
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| **docs** | https://traitlets.readthedocs.io/ |
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| **license** | Modified BSD License |
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Traitlets is a pure Python library enabling:
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- the enforcement of strong typing for attributes of Python objects
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(typed attributes are called _"traits"_);
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- dynamically calculated default values;
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- automatic validation and coercion of trait attributes when attempting a
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change;
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- registering for receiving notifications when trait values change;
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- reading configuring values from files or from command line
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arguments - a distinct layer on top of traitlets, so you may use
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traitlets without the configuration machinery.
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Its implementation relies on the [descriptor](https://docs.python.org/howto/descriptor.html)
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pattern, and it is a lightweight pure-python alternative of the
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[_traits_ library](https://docs.enthought.com/traits/).
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Traitlets powers the configuration system of IPython and Jupyter
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and the declarative API of IPython interactive widgets.
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## Installation
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For a local installation, make sure you have
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[pip installed](https://pip.pypa.io/en/stable/installing/) and run:
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```bash
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pip install traitlets
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```
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For a **development installation**, clone this repository, change into the
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`traitlets` root directory, and run pip:
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```bash
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git clone https://github.com/ipython/traitlets.git
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cd traitlets
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pip install -e .
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```
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## Running the tests
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```bash
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pip install "traitlets[test]"
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py.test traitlets
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```
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## Code Styling
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`traitlets` has adopted automatic code formatting so you shouldn't
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need to worry too much about your code style.
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As long as your code is valid,
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the pre-commit hook should take care of how it should look.
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To install `pre-commit` locally, run the following::
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```
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pip install pre-commit
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pre-commit install
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```
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You can invoke the pre-commit hook by hand at any time with::
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```
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pre-commit run
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```
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which should run any autoformatting on your code
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and tell you about any errors it couldn't fix automatically.
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You may also install [black integration](https://github.com/psf/black#editor-integration)
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into your text editor to format code automatically.
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If you have already committed files before setting up the pre-commit
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hook with `pre-commit install`, you can fix everything up using
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`pre-commit run --all-files`. You need to make the fixing commit
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yourself after that.
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Some of the hooks only run on CI by default, but you can invoke them by
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running with the `--hook-stage manual` argument.
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## Usage
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Any class with trait attributes must inherit from `HasTraits`.
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For the list of available trait types and their properties, see the
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[Trait Types](https://traitlets.readthedocs.io/en/latest/trait_types.html)
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section of the documentation.
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### Dynamic default values
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To calculate a default value dynamically, decorate a method of your class with
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`@default({traitname})`. This method will be called on the instance, and
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should return the default value. In this example, the `_username_default`
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method is decorated with `@default('username')`:
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```Python
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import getpass
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from traitlets import HasTraits, Unicode, default
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class Identity(HasTraits):
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username = Unicode()
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@default('username')
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def _username_default(self):
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return getpass.getuser()
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```
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### Callbacks when a trait attribute changes
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When a trait changes, an application can follow this trait change with
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additional actions.
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To do something when a trait attribute is changed, decorate a method with
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[`traitlets.observe()`](https://traitlets.readthedocs.io/en/latest/api.html?highlight=observe#traitlets.observe).
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The method will be called with a single argument, a dictionary which contains
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an owner, new value, old value, name of the changed trait, and the event type.
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In this example, the `_num_changed` method is decorated with `` @observe(`num`) ``:
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```Python
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from traitlets import HasTraits, Integer, observe
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class TraitletsExample(HasTraits):
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num = Integer(5, help="a number").tag(config=True)
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@observe('num')
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def _num_changed(self, change):
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print("{name} changed from {old} to {new}".format(**change))
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```
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and is passed the following dictionary when called:
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```Python
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{
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'owner': object, # The HasTraits instance
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'new': 6, # The new value
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'old': 5, # The old value
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'name': "foo", # The name of the changed trait
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'type': 'change', # The event type of the notification, usually 'change'
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}
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```
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### Validation and coercion
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Each trait type (`Int`, `Unicode`, `Dict` etc.) may have its own validation or
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coercion logic. In addition, we can register custom cross-validators
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that may depend on the state of other attributes. For example:
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```Python
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from traitlets import HasTraits, TraitError, Int, Bool, validate
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class Parity(HasTraits):
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value = Int()
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parity = Int()
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@validate('value')
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def _valid_value(self, proposal):
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if proposal['value'] % 2 != self.parity:
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raise TraitError('value and parity should be consistent')
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return proposal['value']
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@validate('parity')
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def _valid_parity(self, proposal):
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parity = proposal['value']
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if parity not in [0, 1]:
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raise TraitError('parity should be 0 or 1')
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if self.value % 2 != parity:
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raise TraitError('value and parity should be consistent')
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return proposal['value']
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parity_check = Parity(value=2)
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# Changing required parity and value together while holding cross validation
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with parity_check.hold_trait_notifications():
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parity_check.value = 1
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parity_check.parity = 1
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```
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However, we **recommend** that custom cross-validators don't modify the state
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of the HasTraits instance.
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