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class_proxy-1.1.0
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class_proxy is a transparent proxy for Python
| ویژگی | مقدار |
|---|---|
| سیستم عامل | - |
| نام فایل | class_proxy-1.1.0 |
| نام | class_proxy |
| نسخه کتابخانه | 1.1.0 |
| نگهدارنده | [] |
| ایمیل نگهدارنده | [] |
| نویسنده | Viktor Hercinger |
| ایمیل نویسنده | hercinger.viktor@gmail.com |
| آدرس صفحه اصلی | https://github.com/herczy/class_proxy |
| آدرس اینترنتی | https://pypi.org/project/class_proxy/ |
| مجوز | MIT |
==================================================
class_proxy - a transparent proxy class for Python
==================================================
.. image:: https://badge.fury.io/gh/herczy%2Fclass_proxy.svg
:target: https://badge.fury.io/gh/herczy%2Fclass_proxy
.. image:: https://badge.fury.io/py/class_proxy.svg
:target: https://badge.fury.io/py/class_proxy
.. image:: https://travis-ci.org/herczy/class_proxy.svg?branch=master
:target: https://travis-ci.org/herczy/class_proxy
Introduction
============
`class_proxy` can be used to create simple proxy objects for any value. The
proxy can be any class.
For example, lets say that we have a parser and need to be able to tell where
a value came from (source file name, line number and column). We might have a
`Source` class handling this information:
.. code-block:: python
class Source(object):
def __init__(self, filename, line, column):
self.filename = filename
self.line = line
self.column = column
def __str__(self):
return "file {}, line {}, column {}".format(
self.filename, self.line, self.column
)
def __repr__(self):
return "Source({!r}, {!r}, {!r})".format(
self.filename, self.line, self.column
)
If we attach this source to some class we control, there is no problem. But
what if we want to tell where an integer, string or any scalar, builtin came
from?
The solution is to make a wrapper for the scalar classes:
.. code-block:: python
import class_proxy
class SourceValue(object):
def __init__(self, source):
self.source = source
def __str__(self):
return "{} (from {})".format(
class_proxy.instance(self), self.source
)
def __repr__(self):
return "SourceValue({!r}, {!r})".format(
class_proxy.instance(self), self.source
)
IntProxy = class_proxy.wrap_with(int, SourceValue)
StrProxy = class_proxy.wrap_with(str, SourceValue)
number = IntProxy(123, Source('example', 1, 2))
print(number) # will print: 1 (from file example, line 1, column 2)
string = StrProxy('hello', Source('example', 5, 7))
print(repr(number)) # will print: hello (from file example, line 5, column 7)
other_number = IntProxy(456, Source('example', 7, 8))
print(number < other_number) # will print: True
The `class_proxy.instance` call will return the original, wrapped
instance for the proxy.
The `class_proxy.wrap_with` call will create a proxy class expecting the
wrapped value as the first parameter, while the remaining parameters are passed
to the `SourceValue` constructor.
When retrieving attributes from the proxy class (e.g. `IntProxy`), it
will look up the proxy base class first (e.g. `SourceValue`) and later
the wrapped class (e.g. `int`). This is the reason we care about what
class we're wrapping: we want to be able to wrap the class too, not just
the instance.
In case we're looking up members from the instance, at first we will look it up
from the instance of the proxy class, and then from the wrapped class.
If you don't care about class values, you can also omit the wrapped class:
.. code-block:: python
GenericProxy = class_proxy.wrap_with(SourceValue)
generic = GenericProxy(SomeGenericClass(1, 2), Source('example', 10, 0))
In this case, we wrap the `object`.
There is also a convenience wrapper for the `wrap_with` function, in case
you don't need to define it for multiple wrapped classes:
.. code-block:: python
import class_proxy
@class_proxy.proxy_of(int)
class IntProxy(object):
def clamp(self, minval, maxval):
if self < minval:
result = minval
elif self > maxval:
result = maxval
else:
result = class_proxy.instance(self)
return IntProxy(result)
value = IntProxy(50).clamp(-10, 10)
print(value) # will print: 10
This also has a generic variant:
.. code-block:: python
import class_proxy
@class_proxy.proxy
class Proxy(object):
def map(self, func):
return func(class_proxy.instance(self))
value = Proxy(100)
print(value.map(lambda val: -val)) # will print: -100
Inspiration
===========
`class_proxy` was heavily inspired by `zyga/padme`, an excellent tool for
creating proxy classes. However, `padme` has a few problems:
* It generates a lot of logs, which can not only be annoying, but create odd
infinite recursions when trying to format the wrapped value for a log string.
* The proxied special methods are written out manually, which seems like an
unneccessary thing.
So with these limitations I felt the need to write a similar tool that
addresses the issues above.
History
=======
1.1.0 (2019-03-18)
------------------
* Custom names can be specified for bound class proxies (by default,
it is in the format of <proxy class>[<wrapped class>]).
1.0.1 (2019-03-10)
------------------
* Added caching for created proxies.
1.0.0 (2019-03-09)
------------------
* Inspired by `zyga/padme`.
* Written the basic code.
* Added files to make it more 'project-y'.
* Committed to `github.com`.
نحوه نصب
نصب پکیج whl class_proxy-1.1.0:
pip install class_proxy-1.1.0.whl
نصب پکیج tar.gz class_proxy-1.1.0:
pip install class_proxy-1.1.0.tar.gz