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assignhooks-1.0.2
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مشاهده بیشترتوضیحات
Instrument code to support obj.__preassign__ / obk.__postassign__ methods. Based on assign package by ryankung
| ویژگی | مقدار |
|---|---|
| سیستم عامل | - |
| نام فایل | assignhooks-1.0.2 |
| نام | assignhooks |
| نسخه کتابخانه | 1.0.2 |
| نگهدارنده | [] |
| ایمیل نگهدارنده | [] |
| نویسنده | patgolez10 |
| ایمیل نویسنده | patgolez10@gmail.com |
| آدرس صفحه اصلی | https://github.com/patgolez10/assignhooks |
| آدرس اینترنتی | https://pypi.org/project/assignhooks/ |
| مجوز | MIT |
Description
=====================================
``assignhooks`` allows you to instrument your python code so that assignments to a variable can execute an action before and/or after the fact. For instance:
.. code-block:: python
class SampleClass():
name = ''
def __assignpre__(self, lhs_name, rhs_name, rhs):
print('PRE: assigning %s = %s' % (lhs_name, rhs_name))
# modify rhs if needed before assignment
rhs.name = lhs_name
return rhs
def __assignpost__(self, lhs_name, rhs_name):
print('POST: lhs', self)
print('POST: lhs_name', lhs_name)
print('POST: rhs_name', rhs_name)
print('POST: assigning %s = %s' % (lhs_name, rhs_name))
self.name = lhs_name
b = SampleClass()
c = b
The first assignment would generate a call to `__assignpost__` as `b` still has no contents so there is no information on its class and hence no way to find out if it has an `__assignpre__` method. `__assignpost__` allows `b` to find out its name in this case. In the example above b contains a `SampleClass` instance whose name is initialized to `b` (the variable name)
In the second assignment, b is being assigned on the right-hand-side. As b is already existing we can check if its class provides an `__assignpre__` implementation. `b` knows is being assigned before the fact so we can used `__assignpre__` to check on the assignment or to provide the suitable value to be assigned (the return from `__assignpre__` method)
Applications:
===================
* Can be used to add automatically names to created objects, for debug for instance:
.. code-block:: python
class MyClass:
def __init__(self, val, name=None):
self.val = val
self.name = name
def __assignpost__(self, lhs_name, rhs_name):
if self.name is None:
self.name = lhs_name
# will assign x.name as 'x' automatically
x = MyClass(val=4)
assert x.name == 'x'
* Can be used to control what gets assigned when a specific instance of a class is assigned
How to use it:
===================
Checkout ``test.py`` and ``testmod.py`` under `examples` directory. ``test.py`` contains an example of how to instrument and use ``testmod.py`` module (the module being object of instrumentation).
1. Automatic patch
Suppose that there is a `testmod.py` that contains a module to instrument. Importing 'assignhooks' gives access to 'assignhooks.instrument.start()'. It should be called before the imports you want to instrument. To stop this behavior invoke `assignhooks.instrument.stop()`
Assuming `testmod.py` contains:
``<testmod.py>``
.. code-block:: python
class T():
def __assignpre__(self, lhs_name, rhs_name, rhs):
print('%s has been copied to %s' % (rhs_name, lhs_name))
return rhs
b = T()
c = b
And ``<test.py>``
.. code-block:: python
import assignhooks
assignhooks.instrument.start() # instrument from now on
import testmod
assignhooks.instrument.stop() # stop instrumenting
If executed:
`$ python3 ./test.py`
will produce
`b has been copied to c`
2. manually patch
.. code-block:: python
from assignhooks.patch import patch_module
import testmod
patch_module(test)
Install
=======
Just do:
``pip3 install assignhooks``
How does it work
================
Internally assignhooks.magic replaces __import__ by a new version that after the import patches the module AST tree. It performs the following transformations:
.. code-block:: python
x = T()
gets replaced by:
.. code-block:: python
if True:
x = T()
if hasattr(x, '__assignpost__'):
x.__assignpost__('x', 'T')
and
.. code-block:: python
x = y
gets replaced by:
.. code-block:: python
if True:
if hasattr(y, '__assignpre__'):
x = y.__assignpre__('x', 'y', y)
else:
x = y
if hasattr(x, '__assignpost__'):
x.__assignpost__('x', 'y')
NOTE: that ``if True:`` is only used to group the statements while doing node replacements in the AST.
Notes
=====
* Tested with `Python 3.8.7` on MacOS
Credits
=======
Based on original code from `assign <https://pypi.org/project/assign/>`_ module from **ryankung**. Mainly adapted for my needs to handle object creation. Changes include:
- Original had an ``__assign__`` overload only valid on existing objects (like ``__assignpre__``). Added ``__assignpost__`` to handle object creation cases
- Renamed ``__assign__`` to ``__assignpre__`` and added extra parameters
Known Issues
=============
1. Won't work under `REPL`
2. May slow down import operation. The effect in run-time is the replacement of raw assignments with conditional + assignment + hook
3. May fail when patching standard modules
نحوه نصب
نصب پکیج whl assignhooks-1.0.2:
pip install assignhooks-1.0.2.whl
نصب پکیج tar.gz assignhooks-1.0.2:
pip install assignhooks-1.0.2.tar.gz