Accessing class variables in staticmethods.

[Ramashish Baranwal]

Hi,

I want to access a static variable in a staticmethod. The variable can
be redefined by derived classes and that should be reflected in base's
staticmethod. Consider this trivial example-

class Base:
staticvar = 'Base'

@staticmethod
def printname():
# this doesn't work
# print staticvar
# this does work but derived classes wouldn't behave as I want
print Base.staticvar

class Derived(Base):
staticvar = 'Derived'

Base.printname() # should print 'Base'
Derived.printname() # should print 'Derived'

Any idea on how to go about this? Also from a staticmethod how can I
find out other attributes of the class (not objects)? Do static methods
get some classinfo via some implicit argument(s)?

Thanks in advance,
Ram

[Sam]

On 21 Jan 2007 12:49:17 -0800, Ramashish Baranwal
<ra*************@gmail.comwrote:

class Base:
staticvar = 'Base'

@staticmethod
def printname():
# this doesn't work
# print staticvar
# this does work but derived classes wouldn't behave as I want
print Base.staticvar

class Derived(Base):
staticvar = 'Derived'

Base.printname() # should print 'Base'
Derived.printname() # should print 'Derived'

Any idea on how to go about this? Also from a staticmethod how can I
find out other attributes of the class (not objects)? Do static methods
get some classinfo via some implicit argument(s)?

No, staticmethods get told nothing about the class they're being
defined in. What you want is a classmethod, which gets passed the
class to work with.

Using classmethods, your code becomes:

#untested, bear in mind
class Base:
staticvar = 'Base'

@classmethod
def printname(cls):
print cls.staticvar

class Derived(Base):
staticvar = 'Derived'

Base.printname() #prints 'Base'
Derived.printname() #prints 'Derived'

Incidentally, you can also use cls.__name__ for this purpose, but I
guess that your actual motivation for this is more complicated than
class names.

[Ramashish Baranwal]

Sam wrote:

On 21 Jan 2007 12:49:17 -0800, Ramashish Baranwal
<ra*************@gmail.comwrote:

class Base:
staticvar = 'Base'

@staticmethod
def printname():
# this doesn't work
# print staticvar
# this does work but derived classes wouldn't behave as I want
print Base.staticvar

class Derived(Base):
staticvar = 'Derived'

Base.printname() # should print 'Base'
Derived.printname() # should print 'Derived'

Any idea on how to go about this? Also from a staticmethod how can I
find out other attributes of the class (not objects)? Do static methods
get some classinfo via some implicit argument(s)?

No, staticmethods get told nothing about the class they're being
defined in. What you want is a classmethod, which gets passed the
class to work with.

Using classmethods, your code becomes:

#untested, bear in mind
class Base:
staticvar = 'Base'

@classmethod
def printname(cls):
print cls.staticvar

class Derived(Base):
staticvar = 'Derived'

Base.printname() #prints 'Base'
Derived.printname() #prints 'Derived'

Incidentally, you can also use cls.__name__ for this purpose, but I
guess that your actual motivation for this is more complicated than
class names.

Thanks Sam, using classmethod works. You guessed it correctly, my
actual motivation is more complicated but on the same line.

-Ram