[Tutor] Convert string to variable name

[Tony Giunta]

On Wed, 26 Jan 2005 17:11:59 -0800 (PST), Danny Yoo
<dyoo at hkn.eecs.berkeley.edu> wrote:
> 
> 
> On Wed, 26 Jan 2005, Tony Giunta wrote:
>  
> We can use exec() to create dynamic variable names, but it's almost always
> a bad idea.  Dynamic variable names make it very difficult to isolate
> where variables are coming from in a program. 

Yeah, that's why I was wondering if there was a better way to do it.

> So I'd recommend just using a plain old dictionary: it's not exciting, but
> it's probably the right thing to do.
 
Thanks.  I thought I might have to resort to this.  =)


> Looking back at the code:
> 
> ###
> def generateInstance():
>         class test:
>                 def __init__(self, title, price):
>                         self.title = title
>                         self.price = price
>                 def theTitle(self, title):
>                         return self.title
>                 def thePrice(self, price):
>                         return self.price
> 
>         myName = raw_input("Name: ")
>         myTitle    = raw_input("Title: ")
>         myPrice  = raw_input("Price: ")
> 
>         exec '%s = test("%s", %s)' % (myName, myTitle, myPrice)
> ###
> 
> In Python, we actually can avoid writing attribute getters and setters ---
> the "JavaBean" interface --- because Python supports a nice feature called
> "properties".  See:
> 
>     http://dirtsimple.org/2004/12/python-is-not-java.html
>     http://www.python.org/2.2.2/descrintro.html#property

Ahh.  Thanks for the links, I shall check them out.

> The upside is that we usually don't need methods like theTitle() or
> thePrice() in Python.  Our revised code looks like:
> 
> ###
> class test:
>     def __init__(self, title, price):
>         self.title = title
>         self.price = price
> 
> instances = {}
> 
> def generateInstance():
>     myName  = raw_input("Name: ")
>     myTitle = raw_input("Title: ")
>     myPrice = raw_input("Price: ")
>     instances[myName] = test(myTitle, myPrice)
> ###
>
> If you have more questions, please feel free to ask.  Best of wishes to
> you!

Thanks again Danny.  This is exactly what I was looking for.


tony