Python init doesn't see class variable

Question

I'm feeling more dumb than usual, sorry. Can someone put me out of my misery and explain why __init__ can't see class variable s?

Thanks.

class C:
    s = "but why"

    def __init__(self):
        print(s)

c = C()   
#global DEFAULT_STRING = "(undefined)"

Error

Traceback (most recent call last):
    File "/Users/pvdl/Desktop/FH.sp18python/hw/7/test5.py", line 7, in module
    c = C()
    File "/Users/pvdl/Desktop/FH.sp18python/hw/7/test5.py", line 5, in __init__
    print(s)
NameError: name 's' is not defined

Process finished with exit code 1

You need to use self.s - the function scope isn't nested in the class. — babbageclunk, Jun 15 '18 at 04:29
Possible duplicate of [What is the scope of variables in JavaScript?](https://stackoverflow.com/questions/500431/what-is-the-scope-of-variables-in-javascript) — Peter vdL, Jun 15 '18 at 04:29

score 2 · Answer 1 · answered Jun 15 '18 at 04:52

2

's' is declared as class level variable. It is similar to static variable in JAVA. Variable 's' will be shared by all instances of class C. Hence it can be also accessed using class name(C in this case).

answered Jun 15 '18 at 04:52

Bkmm3

78
6

Reblochon Masque · Answer 2 · 2018-06-15T05:49:33.323

1

You need to use self, or the class name, to access the class variable s

class C:
    s = "but why"

    def __init__(self):
        print(C.s, self.s)


if __name__ == '__main__':

    c = C()

edited Jun 15 '18 at 05:49

answered Jun 15 '18 at 04:40

Reblochon Masque

35,405
10
55
80

Python init doesn't see class variable

2 Answers2