On Mon, 18 Mar 2013 19:00:15 +0530, Laxmikant Chitare wrote:
> Hi,
>
> I have a program that picks module and method name from a configuration
> file and executes the method. I have found two ways to achieve this.
>
> Apporach 1:
> ---------------------------
> moduleName = 'mymodule' #These two variables are read from conf file.
> methodName = 'mymethod'
>
> import operator
> myModule = __import__('mymodule')
> myMethod = operator.methodcaller('mymethod')
> val = myMethod(myModule)
> print val
Since your example code only uses string literals, the best way to write
this would be:
import mymodule
mymodule.mymethod()
But I expect that your example was faulty, and you intended to use
variables:
myModule = __import__(moduleName)
myMethod = operator.methodcaller(methodName)
val = myMethod(myModule)
This would be simpler, and probably faster too:
myModule = __import__(moduleName)
val = getattr(myModule, methodName)()
It's certainly easier to read.
> ---------------------------
>
> Apporach 2:
> ---------------------------
> moduleName = 'mymodule' #These two variables are read from conf file.
> methodName = 'mymethod'
>
> val = eval('myModule.' + methodName + '()')
> print val
This example also fails, since you don't have anything called "myModule".
I suspect you left out a line, myModule = __import__(moduleName).
> ---------------------------
>
> Question: Which approach is better and why. Is there any other better
> way to do this?
You should avoid eval, it is a massive security risk unless you are an
expert, and even then it is still a big security risk. It's also slower
than the alternatives.
--
Steven
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