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Date: Wed, 12 Sep 2012 19:33:12 +0100
From: MRAB <python@mrabarnett.plus.com>
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To: python-list@python.org
Subject: Re: avoid the redefinition of a function
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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"