I ran into unbound method error in python with the code

class Sample(object):
'''This class defines various methods related to the sample'''

    def drawSample(samplesize,List):
        sample=random.sample(List,samplesize)
        return sample

Choices=range(100)
print Sample.drawSample(5,Choices)

After reading many helpful posts here, I figured how I could add @staticmethod above to get the code working. I am python newbie. Can someone please explain why one would want to define static methods? Or, why are not all methods defined as static methods.

Thanks in advance.