I have a program in python that includes a class that takes a function as an argument to the __init__ method. This function is stored as an attribute and used in various places within the class. The functions passed in can be quite varied, and passing in a key and then selecting from a set of predefined functions would not give the same degree of flexibility.
Now, apologies if a long list of questions like this is not cool, but...

Is their a standard way to achieve this in a language where functions aren't first class objects?
Do blocks, like in smalltalk or objective-C, count as functions in this respect?
Would blocks be the best way to do this in those languages?
What if there are no blocks?
Could you add a new method at runtime?
In which languages would this be possible (and easy)?
Or would it be better to create an object with a single method that performs the desired operation?
What if I wanted to pass lots of functions, would I create lots of singleton objects? 
Would this be considered a more object oriented approach?
Would anyone consider doing this in python, where functions are first class objects?
In Smalltalk you'd mostly be using blocks. You can also create classes and instances at runtime.
What is the equivalent of passing functions as arguments using an object oriented approach