Calling a class method in python
I'm looking to call a method in python from a different class like so:
class foo():
def bar(name):
return 'hello %s' % name
def hello(name):
a = foo().bar(name)
return a
Where hello('world') would return 'Hello World'. I'm aware I've done something wrong here, does anyone know what it is? I think it might be the way I'm handling the classes but I haven't got my head around it yet.
In Python, non-static methods explicitly take self as their first argument.
foo.bar() either needs to be a static method:
class foo():
@staticmethod
def bar(name):
return 'hello %s' % name
or has to take self as its first argument:
class foo():
def bar(self, name):
return 'hello %s' % name
What happens is that in your code, name gets interpreted as the self parameter (which just happens to be called something else). When you call foo().bar(name) , Python tries to pass two arguments ( self and name ) to foo.bar() , but the method only takes one.
You are missing the instance parameter in your method definition:
class foo():
def bar(self, name):
return 'hello %s' % name
or if you don't intend to use any part of the foo instance declare the method as a static method. There's a nice explanation between the differences here.
If it's supposed to be a class method, then you should have used the classmethod decorator and a cls argument to bar . But that makes no sense in this case, so you might have wanted a staticmethod instead.
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