求助！NameError: name 'FooClass' is not defined。

输入以下代码报错：
class FooClass(object):
"""my very first class: FooClass"""
version = 0.1 #class (data) attribute
def __init__(self, nm = 'John Doe'):
"""constructor"""
self.name = nm #class instance (data) attribute
print 'Created a class omstance for', nm
def showname(self):
"""display instance attribute and class name"""
print 'Your name is', self.name
print 'My name is', self.__class__.__name__
def showver(self):
"""display class (static) attribute"""
print self.version #reference FooClass.version
def addme2me(self, x): #does not use 'self'
"""apply + operation to argument"""
return x + x
fool = FoolClass()
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
fool = FoolClass()
NameError: name 'FoolClass' is not defined
文件名“FooClass.py”，版本python2.7。