Python: modifying class from an inside function

[stargazer3]

I feel very stupid right now. Should be an easy question, but I googled it to no avail.
Basically, I have an class.object in my code which should be managed by a class.function
For example, I want the following code:

class Z:
        a=0
        def mod(self):
                self.a=self.a+1

t=Z
print Z.a
t.mod
print Z.a
t.a+=1
print Z.a

to return "0 1 2", instead of "0 0 1"
Can it be done in Python? If yes, what is the Python way of doing so? If no, why not?

 

[phyzguy]

I feel very stupid right now. Should be an easy question, but I googled it to no avail.
Basically, I have an class.object in my code which should be managed by a class.function
For example, I want the following code:

class Z:
        a=0
        def mod(self):
                a
                a=a+1

t=Z
print Z.a
t.mod
print Z.a
t.a+=1
print Z.a

to return "0 1 2", instead of "0 0 1"
Can it be done in Python? If yes, what is the Python way of doing so? If no, why not?

I think you have several things wrong.
First, inside the mod function, I think you should have: self.a = self.a + 1
Second, when you create the object t as an instance of class Z, you should have: t = Z()
This invokes the constructor of Z.
Third, when you call the function mod you should have: t.mod()
Fourth, don't you want print t.a instead of print Z.a ??

 

[stargazer3]

Oh, I'm so sorry, was writing it in a hurry!
Yes, it's working right now, thanks!
...
I think that my face is quite red now.

 

[gsal]

Also, you need to keep in mind the difference between a class and an instance of it...class Z is already an object in its own right that can be dealt even before creating the instance t...so, you actually have 2 things going on and you need to learn how to deal with them...you have class attributes and instance attributes...go back and re-read classes...

 

[Solkar]

## @file static.py
import sys

class Z: # declares a "class object"
    a = 0 # inited when Z is seen first
    @staticmethod
    def mod():
        Z.a += 1

t = Z # t is an alias reference on the Z "class object"
sys.stderr.write('\t' + str(t) + '\n')

print(Z.a)
t.mod()
print(Z.a)
t.a += 1
print(Z.a)

u = Z() # u is a Z instance
sys.stderr.write('\t' + str(u) + '\n')

u.mod() # actually works, contrary to C++ or Java statics! 
sys.stderr.write('\t' + str(Z.a) + '\n')

Usage

python static.py

Output:

	__main__.Z
0
1
2
	<__main__.Z instance at 0x7f5233334488>
	3

Tested with python 2.7 and python 3.1 on x86_64 Debian "squeeze" Linux

Regards, S.

P.S.: Pls keep in mind that "print" without brackets is outdated.