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python interfaces

On Programmer » Python

9,892 words with 9 Comments; publish: Thu, 01 May 2008 01:09:00 GMT; (200109.38, « »)

Hi,

Probably it has been asked before, but I'll still ask.

Why doesn't python provide interfaces trough its standard library? Or it

was ever proposed to be included in the language?

Zope's implementation seems pretty flexible and straightforward.

Thanks.

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  • 9 Comments
    • On Jan 4, 3:59 pm, hyperboreean <hyperbore....python.todaysummary.com.nerdshack.com> wrote:

      > Hi,

      > Probably it has been asked before, but I'll still ask.

      > Why doesn't python provide interfaces trough its standard library? Or it

      > was ever proposed to be included in the language?

      > Zope's implementation seems pretty flexible and straightforward.

      > Thanks.

      Python 3.0 will introduce Abstract Base Classes:

      http://www.python.org/dev/peps/pep-3119/

      #1; Thu, 01 May 2008 01:10:00 GMT
    • hyperboreean <hyperboreean.python.todaysummary.com.nerdshack.com> wrote:

      >Why doesn't python provide interfaces trough its standard library?

      Because they're pointless. Java interfaces are a hack around the

      complexities of multiple inheritence. Python does multiple

      inheritence Just Fine (give or take the subtleties of super()) so

      does not need them.

      Interfaces used purely with the idea of type safety provide

      precious little gain for the added clutter and inconvenience.

      Compare them to Java's requirement for explicit declaration of

      exceptions thrown in a method signature, if you will.

      \S -- siona.python.todaysummary.com.chiark.greenend.org.uk -- http://www.chaos.org.uk/~sion/

      "Frankly I have no feelings towards penguins one way or the other"

      -- Arthur C. Clarke

      her nu become se bera eadward ofdun hlddre heafdes bce bump bump bump

      #2; Thu, 01 May 2008 01:11:00 GMT
    • Sion Arrowsmith wrote:

      > hyperboreean <hyperboreean.python.todaysummary.com.nerdshack.com> wrote:

      > Because they're pointless.

      Wrong. I'm using Eclipse with the Java Development Tools (JDT) who do

      a wonderful job using interfaces to perform lots of checking, warning

      and code generation *nearly in real time while I am editing my code*.

      Because JDT knows interfaces it knows what to do and to suggest. An

      interface is a software specification allowing you to use a software

      package without extensive code studies. This is a good thing.

      > Java interfaces are a hack around the complexities of multiple

      > inheritence.

      A hack is something applied subsequently to solve a software problem while

      avoiding large changes. Java interfaces originate from careful language

      design. You are free to dislike Java interfaces but calling them a hack is

      just plain wrong.

      Once software becomes really big interfaces are very useful to handle

      complexity. Ever wondered why the Zope people introduced interfaces in

      their Python code?

      > Interfaces used purely with the idea of type safety provide

      > precious little gain for the added clutter and inconvenience.

      An interface is a software specification allowing you to use a software

      package without extensive code studies. This is a good thing. Interfaces

      have nothing to do with multiple inheritance. They just tell you how to

      connect, how to plug in.

      Regards/Gruesse,

      Peter Maas, Aachen

      E-mail 'cGV0ZXIubWFhc0B1dGlsb2cuZGU=\n'.decode('base64')

      #3; Thu, 01 May 2008 01:12:00 GMT
    • Sion Arrowsmith wrote:

      > hyperboreean <hyperboreean.python.todaysummary.com.nerdshack.com> wrote:

      > Because they're pointless.

      Wrong. I'm using Eclipse with the Java Development Tools (JDT) who do

      a wonderful job using interfaces to perform lots of checking, warning

      and code generation *nearly in real time while I am editing my code*.

      Because JDT knows interfaces it knows what to do and to suggest.

      > Java interfaces are a hack around the complexities of multiple

      > inheritence.

      A hack is something applied subsequently to solve a software problem while

      avoiding large changes. Java interfaces originate from careful language

      design. You are free to dislike Java interfaces but calling them a hack is

      just plain wrong.

      Once software becomes really big interfaces are very useful to handle

      complexity. Ever wondered why the Zope people introduced interfaces in

      their Python code?

      > Interfaces used purely with the idea of type safety provide

      > precious little gain for the added clutter and inconvenience.

      An interface is a software specification allowing you to use a software

      package without extensive code studies. This is a good thing. Interfaces

      have nothing to do with multiple inheritance and are not about type safety

      in the first place. They just tell you how to connect, how to plug in.

      Regards/Gruesse,

      Peter Maas, Aachen

      E-mail 'cGV0ZXIubWFhc0B1dGlsb2cuZGU=\n'.decode('base64')

      #4; Thu, 01 May 2008 01:13:00 GMT
    • On Jan 4, 6:01 pm, Sion Arrowsmith <si....python.todaysummary.com.chiark.greenend.org.uk>

      wrote:

      > hyperboreean <hyperbore....python.todaysummary.com.nerdshack.com> wrote:

      > Because they're pointless. Java interfaces are a hack around the

      > complexities of multiple inheritence. Python does multiple

      > inheritence Just Fine (give or take the subtleties of super()) so

      > does not need them.

      >

      Hallo,

      Interfaces are a extremly smart Design Principle in static typed

      languages

      like Java and C++.

      C++ support Interfaces in a form of abstract base classes. They aren't

      pointless.

      They force the user of a framework to use it in a defined way. You

      prescribe in

      the base class the usage of a classsystem and allow only in derived

      classes

      to variate the behavior.

      To appreciate Interfaces look at the Template Methode Pattern (http://

      en.wikipedia.org/wiki/Template_method_pattern )

      or especially at the Non Virtual Interface ( http://www.gotw.ca/publications/mill1

      8.htm

      ) Idiom from Herb Sutter.

      To be short C++ support Interfaces and multiple inheritace.

      Greetings Rainer

      #5; Thu, 01 May 2008 01:14:00 GMT
    • r.grimm.python.todaysummary.com.science-computing.de wrote:

      > Interfaces are a extremly smart Design Principle in static typed

      > languages like Java and C++.

      that's somewhat questionable in itself, and even more questionable as an

      argument for interfaces in Python.

      I'd recommend anyone who thinks that they cannot program without formal

      interfaces to try using Python as Python for a while, before they try

      using it as something else. you might be surprised over how easy it is

      to build robust stuff without having to add lots of extra constraints to

      your code.

      </F>

      #6; Thu, 01 May 2008 01:15:00 GMT
    • On Sat, 05 Jan 2008 23:31:02 -0800, r.grimm wrote:

      > They force the user of a framework to use it in a defined way.

      This is the arrogance of the provider thinking that he can anticipate all

      the needs of the user.

      Even when interfaces exist, they should be there to guide the user rather

      than to force the user. A user should be able to refuse to implement the

      interface, if the user knows that full implmentation is not necessary, or

      dangerous. Frankly, a lot of interfaces suck. The user is often a lot

      smarter than the provider, and nearly always knows his needs better. My

      sympathies in these matters are entirely on the user's side--I know

      that's very different from the philosophies of languages like C++ and

      Java.

      There's a time and a place for interfaces. Your average run-of-the-mill

      polymorphism is not it. Usually interfaces are more of a burden than a

      benefit, especially in code that is young and still subject to lots of

      redesign and refactoring.

      And ehen interfaces do make sense, such as in a plugin system or a

      complex framework, the user should be free to ignore the interface at his

      own risk.

      Carl Banks

      #7; Thu, 01 May 2008 01:16:00 GMT
    • Sion Arrowsmith a crit :

      > hyperboreean <hyperboreean.python.todaysummary.com.nerdshack.com> wrote:

      >

      >

      > Because they're pointless.

      (snip rant about Java's "interfaces")

      Hem... Zope3's "interface" system is not exactly the same thing as

      Java's one.

      #8; Thu, 01 May 2008 01:17:00 GMT
    • On Jan 6, 11:01 am, Fredrik Lundh <fred....python.todaysummary.com.pythonware.com> wrote:

      > r.gr....python.todaysummary.com.science-computing.de wrote:

      > that's somewhat questionable in itself, and even more questionable as an

      > argument for interfaces in Python.

      > I'd recommend anyone who thinks that they cannot program without formal

      > interfaces to try using Python as Python for a while, before they try

      > using it as something else. you might be surprised over how easy it is

      > to build robust stuff without having to add lots of extra constraints to

      > your code.

      > </F>

      Hallo,

      I argued, that Interface and multiple inheritance are different

      things and

      especially, that Interfaces are very useful in staticially typed

      languages.

      In such languages like Java and C++ you need a formalismen to guide

      the user.

      You may call it extension point, pure virtual function or abstract

      methode.

      Sorry for the misunderstanding, I argued for Interface in heavyweight

      static

      typed languages and nor for lightweight dynamic typed languages like

      python.

      They aren't pointless and a hack.

      Greetings Rainer

      #9; Thu, 01 May 2008 01:18:00 GMT