dynamically modify help text
Brian Blais
I know that the help text for an object will give a description of
every method based on the doc string. Is there a way to add
something to this text, specific to an object, but generated at run-
time? I have an object that reads a file, and I would like part of
that file to be shown if one does: help(myobject)
thanks,
Brian Blais
--
Brian Blais
bbl...@bryant.edu
http://web.bryant.edu/~bblais
http://bblais.blogspot.com/
Red Forks
On Monday, June 28, 2010, Brian Blais <bbl...@bryant.edu> wrote:
> Hello,
>
> I know that the help text for an object will give a description of every method based on the doc string. Is there a way to add something to this text, specific to an object, but generated at run-time? I have an object that reads a file, and I would like part of that file to be shown if one does: help(myobject)
>
>
> thanks,
>
> Brian Blais
>
> --
> Brian Blais
> bbl...@bryant.edu
> http://web.bryant.edu/~bblais
> http://bblais.blogspot.com/
>
>
>
Brian Blais
On Jun 27, 2010, at 22:37 , Red Forks wrote:
> Read you doc file and set the __doc__ attr of the object you want
> to change.
>
> On Monday, June 28, 2010, Brian Blais <bbl...@bryant.edu> wrote:
>> I know that the help text for an object will give a description of
>> every method based on the doc string. Is there a way to add
>> something to this text, specific to an object, but generated at
>> run-time? I have an object that reads a file, and I would like
>> part of that file to be shown if one does: help(myobject)
>>
>>
python file:
#=============
class A(object):
pass
help_text="this is some text"
a=A()
a.__doc__=help_text
#=============
in ipython:
shows up here:
In [5]:a?
Type: A
Base Class: <class '__main__.A'>
String Form: <__main__.A object at 0x13270f0>
Namespace: Interactive
File: /Library/Frameworks/Python.framework/Versions/5.0.0/
lib/python2.5/site-packages/IPython/FakeModule.py
Docstring:
this is some text
but not with the help command:
In [6]:help(a)
Help on A in module __main__ object:
class A(__builtin__.object)
| Data descriptors defined here:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
also does the same thing with the regular python prompt.
is there a reason for this?
Chris Rebert
__doc__ is normally defined on classes, e.g. `A`, not instances, e.g.
`a`. help() looks for __doc__ accordingly.
Cheers,
Chris
--
http://blog.rebertia.com
Benjamin Kaplan
Just to save the OP some trouble later on: this optimization is done
for most of the __*__ methods. Overriding __add__ on an instance won't
change the behavior of a + b.
Emile van Sebille
> Just to save the OP some trouble later on: this optimization is done
> for most of the __*__ methods. Overriding __add__ on an instance won't
> change the behavior of a + b.
ActivePython 2.4.1 Build 247 (ActiveState Corp.) based on
Python 2.4.1 (#65, Jun 20 2005, 17:01:55) [MSC v.1310 32 bit (Intel)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> class Test: pass
...
>>> i = Test()
>>> i+1
Traceback (most recent call last):
File "<stdin>", line 1, in ?
TypeError: unsupported operand type(s) for +: 'instance' and 'int'
>>> def __add__(self): return 6
...
>>> i.__add__ = __add__
>>> i+1
6
>>>
Was this in reference to a specific python version?
Emile
Thomas Jollans
ahem
Python 2.5.5 (r255:77872, Apr 21 2010, 08:40:04)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class A(object):
... def __add__(self, other):
... return "indeed"
...
>>> a = A()
>>> a + 1
'indeed'
>>> def new__add__(other):
... return "not at all"
...
>>> a.__add__ = new__add__
>>> a.__add__(1)
'not at all'
>>> a+1
'indeed'
>>>
>>>
>>> class B:
... def __add__(self, other):
... return 'now this is old-style'
...
>>> b = B()
>>> b+1
'now this is old-style'
>>> b.__add__ = new__add__
>>> b+1
'not at all'
>>>
I hate the fact that Python 2.x has two types of classes. Good riddance.
-- Thomas
Stephen Hansen
> On 6/28/2010 12:02 PM Benjamin Kaplan said...
>> Just to save the OP some trouble later on: this optimization is done
>> for most of the __*__ methods. Overriding __add__ on an instance won't
>> change the behavior of a + b.
>
> ActivePython 2.4.1 Build 247 (ActiveState Corp.) based on
> Python 2.4.1 (#65, Jun 20 2005, 17:01:55) [MSC v.1310 32 bit (Intel)] on
> win32
> Type "help", "copyright", "credits" or "license" for more information.
> >>> class Test: pass
> ...
> >>> i = Test()
> >>> i+1
> Traceback (most recent call last):
> File "<stdin>", line 1, in ?
> TypeError: unsupported operand type(s) for +: 'instance' and 'int'
> >>> def __add__(self): return 6
> ...
> >>> i.__add__ = __add__
> >>> i+1
> 6
> >>>
>
> Was this in reference to a specific python version?
No, its a reference to new-style vs old-style classes. If Test inherits
from object, it won't work. Its one of several subtle behaviorial
differences between old/new classes.
--
... Stephen Hansen
... Also: Ixokai
... Mail: me+list/python (AT) ixokai (DOT) io
... Blog: http://meh.ixokai.io/
Christian Heimes
> >>> i+1
> 6
> >>>
>
> Was this in reference to a specific python version?
This doesn't work with new style classes and thus not in Python 3.x.
Subclass from object and you'll see the difference.
Christian
Brian Blais
>> On Jun 27, 2010, at 22:37 , Red Forks wrote:
>>> Read you doc file and set the __doc__ attr of the object you want to
>>> change.
>>>
>
> __doc__ is normally defined on classes, e.g. `A`, not instances, e.g.
> `a`. help() looks for __doc__ accordingly.
>
> Cheers,
> Chris
so that gets back to my original question: can I change this text at
runtime. Doesn't look like I can, because it is defined for classes
rather than instances. Am I thinking about this correctly?
bb
Ben Finney
> On Jun 28, 2010, at 14:25 , Chris Rebert wrote:
> > __doc__ is normally defined on classes, e.g. `A`, not instances,
> > e.g. `a`. help() looks for __doc__ accordingly.
>
> so that gets back to my original question: can I change this text at
> runtime. Doesn't look like I can, because it is defined for classes
> rather than instances. Am I thinking about this correctly?
Classes are objects. You can change the ‘__doc__’ attribute of a class
object the same as you'd change it for any other object::
A.__doc__ = "new docstring"
--
\ “All television is educational television. The question is: |
`\ what is it teaching?” —Nicholas Johnson |
_o__) |
Ben Finney
Steven D'Aprano
> Brian Blais <bbl...@bryant.edu> writes:
>
>> On Jun 28, 2010, at 14:25 , Chris Rebert wrote:
>> > __doc__ is normally defined on classes, e.g. `A`, not instances, e.g.
>> > `a`. help() looks for __doc__ accordingly.
>>
>> so that gets back to my original question: can I change this text at
>> runtime. Doesn't look like I can, because it is defined for classes
>> rather than instances. Am I thinking about this correctly?
>
> Classes are objects. You can change the ‘__doc__’ attribute of a class
> object the same as you'd change it for any other object::
>
> A.__doc__ = "new docstring"
True, but what you can't do is:
a = A()
a.__doc__ = "new docstring"
unless you jump through hoops with __getattribute__ or descriptors.
--
Steven
Thomas Jollans
> Brian Blais <bbl...@bryant.edu> writes:
>
>> On Jun 28, 2010, at 14:25 , Chris Rebert wrote:
>>> __doc__ is normally defined on classes, e.g. `A`, not instances,
>>> e.g. `a`. help() looks for __doc__ accordingly.
>>
>> so that gets back to my original question: can I change this text at
>> runtime. Doesn't look like I can, because it is defined for classes
>> rather than instances. Am I thinking about this correctly?
>
> Classes are objects. You can change the ‘__doc__’ attribute of a class
> object the same as you'd change it for any other object::
>
> A.__doc__ = "new docstring"
>
No, you can't. Well, yeah, you can. But you can't. But you can. Ahrgh
I want Python 2.x to go away. It's so inconsistent and silly.
% python2.6
Python 2.6.5+ (release26-maint, Jun 28 2010, 19:46:36)
[GCC 4.4.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> class OLD: pass
...
>>> class NEW(object): pass
...
>>> OLD.__doc__ = "foo"
>>> NEW.__doc__ = "bar"
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: attribute '__doc__' of 'type' objects is not writable
>>>
Aahz
Thomas Jollans <tho...@jollans.com> wrote:
>
>% python2.6
>Python 2.6.5+ (release26-maint, Jun 28 2010, 19:46:36)
>[GCC 4.4.4] on linux2
>Type "help", "copyright", "credits" or "license" for more information.
>>>> class OLD: pass
>...
>>>> class NEW(object): pass
>...
>>>> OLD.__doc__ = "foo"
>>>> NEW.__doc__ = "bar"
>Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
>AttributeError: attribute '__doc__' of 'type' objects is not writable
>>>>
I'd argue that's a bug -- feel free to file one. I think this might
even be fixable in 2.7.1.
--
Aahz (aa...@pythoncraft.com) <*> http://www.pythoncraft.com/
"If you don't know what your program is supposed to do, you'd better not
start writing it." --Dijkstra