Python how name variable inside a class

lugoteehalt · 10-21-2003, 04:30 AM

Learning/relearning Python. Grotesquely simple question:

How do I get hold of the value of y from outside this class?

Code:

#! /usr/bin/python

# Try to work out how classes are called.
# classUnderstand.py

class C:
          def __init__(self, x):
                  print "init called", self, x
          def f(self, x):
                  print "f called", self, x
                  y = x + 1

....I want to put something like:
print C(4).f(4).y
anticipating it will print the number 5. It never will.

How do I name the value of y? Does the class need changing somehow?

Thanks any help.

abrb220 · 10-21-2003, 04:53 AM

Also new to python but I got it to work :
----------------------------------------------
#! /usr/bin/python
# Try to work out how classes are called.
# classUnderstand.py
class C:
def __init__(self, x):
print "init called", self, x
def f(self, x):
print "f called", self, x
self.y = x + 1
return self

print C(4).f(4).y
---------------------------------------------
What do you think?

abrb220 · 10-21-2003, 04:55 AM

omg the Indentation got screwed up.Sorry.

lugoteehalt · 10-21-2003, 05:06 AM

Amazing! I'll have to try and work out what it all means. Perhaps was assuming the problem had to do with classes when it really had to do with 'return'. Maybe you have to use it in functions as well. Thanks.

abrb220 · 10-21-2003, 06:08 AM

The only reason to "return self" is to be able to make the call :
C(4).f(4).y

If you do this :

a = C(4) # create instance of class
a.f(4) # call func f
print a.y

You do not need the "return self"

lugoteehalt · 10-22-2003, 05:11 AM

Right, that's the bit I was after, now I've thought about it. Find it a little counter-intuitive. Thanks.