未定义功能混乱

Question

我有这段代码在这里，我想知道为什么我得到“total_with_tax未定义”

发生这种情况时，我做的：

c = Customer() 
c.print_bill() --> this is where I get the error 

代码：

class Customer: 
def __init__(self): 
    self.total = 0 
    self.items_ordered = str("") 

def add_to_order(self, NameOfItem, CostOfItem): 
    self.total += CostOfItem 
    self.items_ordered = self.items_ordered + (str(NameOfItem) + ", ") 

def total_with_tax(self): 
    return ((self.total * 0.13) + self.total) 

def print_bill(self): 
    print("----------------------------------------------") 
    print(self.items_ordered) 
    print("$%d" %(self.total)) 
    print("$%d" %(total_with_tax())) 
    print("----------------------------------------------") 

Answer 1

您需要将total_with_tax加上self，如下所示：

print("$%d" % self.total_with_tax())