Re: [python-control-discuss] __repr__

[Rene v. P. <ren...@gm...>]

Numpy does this:

Imported NumPy 1.6.2, SciPy 0.10.1, Matplotlib 1.0.1
Type "scientific" for more details.
>>> import numpy as np
>>> x = np.arange(0, 9)
>>> x
array([0, 1, 2, 3, 4, 5, 6, 7, 8])
>>> y = array([0, 1, 2, 3, 4, 5, 6, 7, 8])
>>> y
array([0, 1, 2, 3, 4, 5, 6, 7, 8])
>>> print x
[0 1 2 3 4 5 6 7 8]

But for big arrays

>>> y = np.arange(0, 100, 0.01)


>>> y

array([ 0.00000000e+00, 1.00000000e-02, 2.00000000e-02, ...,

         9.99700000e+01, 9.99800000e+01, 9.99900000e+01])


I guess for python-control the proper thing is something like:


>>> h

TransferFunction([1], [1, 2, 1])


I wouldn't have known the distinction between __repr__ and __str__ either,
but stumbled upon it since I am currently teaching python to 1st year
undergrads. I also teach control theory to 2nd year, of which a quarter is
using Python (from last year's Python programming trial) and the rest is
using Matlab.


René


Associate Professor

Aerospace Engineering

Delft University of Technology


On 12 June 2013 04:26, Ryan Krauss <rk...@si...> wrote:

> > __repr__ is ideally for printing a representation that can directly be
> fed back into Python to > re-create the object.
>
> I guess I didn't realize this convention.  Like you said, I don't think it
> is typically followed.  When I want to look at a variable at the IPython
> prompt, I am not used to having to type print in front of it.
>
>
> --
> Ryan Krauss, Ph.D.
> Associate Professor
> Mechanical Engineering
> Southern Illinois University Edwardsville
>
>
> On Tue, Jun 11, 2013 at 2:37 PM, Rene van Paassen <
> ren...@gm...> wrote:
>
>> __str__ is for pretty printing
>> __repr__ is ideally for printing a representation that can directly be
>> fed back into Python to re-create the object. Many objects don't implement
>> that, though, it is basically limited to the standard Python objects.
>>
>>
>> On 10 June 2013 17:53, Ryan Krauss <rk...@si...> wrote:
>>
>>> I probably won't get to this one for a few weeks (I have a conference
>>> and another paper coming up), but I would like to contribute a __repr__
>>> method for TransferFunctions if it would be welcome.  I personally would
>>> prefer that when I type the name of a TransferFunction instance and hit
>>> enter that it pretty print an ascii numerator and denominator and a
>>> horizontal line.  It might be tricky to do it really nicely with exponents,
>>> but this is what happend now:
>>>
>>> In [2]: G = control.TransferFunction(1,[1,2])
>>>
>>> In [3]: G
>>> Out[3]: <control.xferfcn.TransferFunction instance at 0x10e94cf80>
>>>
>>> I then have to ask ro G.num and G.den separately, which I personally
>>> don't like.
>>>
>>> I see that there is a __str__ method which pretty much does what I would
>>> want, so that "print G" gives me an ascii representation.
>>>
>>> Is there any reason not to have __repr__ simply call __str__?  Is there
>>> some historical reason to have one and not the other?
>>>
>>> --
>>> Ryan Krauss, Ph.D.
>>> Associate Professor
>>> Mechanical Engineering
>>> Southern Illinois University Edwardsville
>>>
>>>
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>>
>> --
>> René van Paassen        | ______o____/_|     Ren...@gm...
>>                        <[___\_\_-----<               t: +31 15 2628685
>>                         |  o'                   mobile: +31 6 39846891
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-- 
René van Paassen        | ______o____/_|     Ren...@gm...
                       <[___\_\_-----<               t: +31 15 2628685
                        |  o'                   mobile: +31 6 39846891