Python 2.7中的return

Question

刚才那个代码有误，我把全部贴出来
classintSet(object):
def__init__(self):
#creatanemptysetofintegers
self.vals=[]
definsert(self,e):
#assumeeisaninterger,andinsertit
ifnot(einself.vals):
self.vals.append(e)
defmember(self,e):
returneinself.vals
defremove(self,e):
try:
self.vals.remove(e)
except:
raiseValueError(str(e)+'notfound')
def__str__(self):
#returnastringrepresentationofself
self.vals.sort()
return"{"+','.join([str(e)foreinself.vals])+"}"
初学，return后面这一句依然没看懂.join在这里是method吗，这个格式是怎么回事

Answer 1

return'{'+','[str(e)foreinself.vals]+'}'这句代码是错的1，','[str(e)foreinself.vals]，是不是在','和[str(e)foreinself.vals]中间掉了符号；2，字符串不能和list相加。猜想：应该是想这么写的"{"+','.join([str(e)foreinself.vals])+"}"建议你把self.vals的值print出来，然后再看下