lazy evaluation of a variable

Gelonida N gelonida at gmail.com
Sun Jun 17 23:35:12 CEST 2012


Hi,

I'm not sure whether what I ask for is impossible, but would know how 
others handle such situations.



I'm having a module, which should lazily evaluate one of it's variables.
Meaning that it is evaluated only if anybody tries to use this variable.

At the moment I don't know how to do this and do therefore following:


####### mymodule.py #######
var = None

def get_var():
     global var
     if var is not None:
         return var
     var = something_time_consuming()



Now the importing code would look like

import mymodule
def f():
     var = mymodule.get_var()

The disadvantage is, that I had to change existing code directly 
accessing the variable.


I wondered if there were any way to change mymodule.py such, that the 
importing code could just access a variable and the lazy evaluation 
would happen transparently.

import mymodule
def f():
     var = mymodule.var



Thanks in advance for you suggestions








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