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Re: avoid the redefinition of a function

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On Thu, 13 Sep 2012 10:23:22 +0200, Peter Otten wrote:

> MRAB wrote:
> 
>> On 12/09/2012 19:04, Alister wrote:
>>> On Wed, 12 Sep 2012 18:56:46 +0200, Jabba Laci wrote:
>>>
>>>>> For example:
>>>>>
>>>>> def install_java():
>>>>>    pass
>>>>>
>>>>> def install_tomcat():
>>>>>    pass
>>>>
>>>> Thanks for the answers. I decided to use numbers in the name of the
>>>> functions to facilitate function calls. Now if you have this menu
>>>> option for instance:
>>>>
>>>> (5) install mc
>>>>
>>>> You can type just "5" as user input and step_5() is called
>>>> automatically. If I use descriptive names like install_java() then
>>>> selecting a menu point would be more difficult. And I don't want
>>>> users to type "java", I want to stick to simple numbers.
>>>>
>>>> Laszlo
>>>
>>> No No NO!
>>> you cant just pass user input to system calls without validating it
>>> first (google sql injection for examples of the damage unsanitised
>>> input can cause, it is not just as SQL problem)
>>>
>>> it is just as easy so select a reasonably named function as a bad one
>>>
>>> option=raw_input('select your option :')
>>>
>>> if option =="1": install_java()
>>> if option =="2": install_other()
>>>
>>> alternatively you cold add your functions into a dictionary an call
>>> them from that
>>>
>>> opts={'1':install java,'2':install_other}
>>>
>>> option=raw_input('select your option :')
>>> opts[option]
>>>
>>> Poorly named functions are a major example of poor programming style.
>>>
>>> one of the fundamental pillars for python is readability!
>>>
>> Or you could do this:
>> 
>> 
>> def install_java():
>>      "Install Java"
>>      print "Installing Java"
>> 
>> def install_tomcat():
>>      "Install Tomcat"
>>      print "Installing Tomcat"
>> 
>> menu = [install_java, install_tomcat]
>> 
>> for index, func in enumerate(menu, start=1):
>>      print "{0}) {1}".format(index, func.__doc__)
>> 
>> option = raw_input("Select your option : ")
>> 
>> try:
>>      opt = int(option)
>> except ValueError:
>>      print "Not a valid option"
>> else:
>>      if 1 <= opt < len(menu):
>>          menu[opt - 1]()
>>      else:
>>          print "Not a valid option"
> 
> I'd still argue that a function index is the wrong approach. You can use
> tab completion to make entering descriptive names more convenient:
> 
> import cmd
> 
> class Cmd(cmd.Cmd):
>     prompt = "Enter a command (? for help): "
> 
>     def do_EOF(self, args):
>         return True
>     def do_quit(self, args):
>         return True
> 
>     @classmethod def install_command(class_, f):
>         def wrapped(self, arg):
>             if arg:
>                 print "Discarding argument {!r}".format(arg)
>             return f()
> 
>         wrapped.__doc__ = f.__doc__
>         wrapped.__name__ = f.__name__ class_._add_method("do_" +
>         f.__name__, wrapped)
>         return f
> 
>     @classmethod def _add_method(class_, methodname, method):
>         if hasattr(class_, methodname):
>             raise ValueError("Duplicate command
>             {!r}".format(methodname))
>         setattr(class_, methodname, method)
> 
> command = Cmd.install_command
> 
> @command def install_java():
>      "Install Java"
>      print "Installing Java"
> 
> @command def install_tomcat():
>      "Install Tomcat"
>      print "Installing Tomcat"
> 
> if __name__ == "__main__":
>     Cmd().cmdloop()

To be honest I prefer the "if X do Y" approach for readability but a 
dictionary can be undated dynamically & used to automatically create the 
menu so it can have its place


-- 
I'll see you... on the dark side of the moon...
		-- Pink Floyd

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Re: avoid the redefinition of a function Jabba Laci <jabba.laci@gmail.com> - 2012-09-12 18:56 +0200
  Re: avoid the redefinition of a function Alister <alister.ware@ntlworld.com> - 2012-09-12 18:04 +0000
    Re: avoid the redefinition of a function MRAB <python@mrabarnett.plus.com> - 2012-09-12 19:33 +0100
    Re: avoid the redefinition of a function D'Arcy Cain <darcy@druid.net> - 2012-09-12 17:49 -0400
    Re: avoid the redefinition of a function Peter Otten <__peter__@web.de> - 2012-09-13 10:23 +0200
      Re: avoid the redefinition of a function Alister <alister.ware@ntlworld.com> - 2012-09-13 17:59 +0000

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