I am trying to make a toy singleton in python to learn the ins and outs of the language and am running into a problem with how python works. I declare the class like this
class ErrorLogger:
# Singleton that provides logging to a file
instance = None
def getInstance():
# Our singleton "constructor"
if instance is None :
print "foo"
when I call it with
log = ErrorLogger.getInstance()
I get
File "/home/paul/projects/peachpit/src/ErrorLogger.py", line 7, in getInstance
if instance is None :
UnboundLocalError: local variable 'instance' referenced before assignment
What is going on here, shouldn't instance be statically assigned Null? What would be the right way to do this?
1 Answer
You have to call it with ErrorLogger prefix as it is a static variable.
class ErrorLogger:
# Singleton that provides logging to a file
instance = None
@staticmethod
def getInstance():
# Our singleton "constructor"
if ErrorLogger.instance is None :
print "foo"
