所以，基本上我的代码在打印我希望它打印的语句后打印 None 。 我怎样才能阻止这个 None 打印

Question

所以，基本上我的代码在打印我希望它打印的语句后打印 None 。 我怎样才能阻止这个 None 打印

class Panda:
    def __init__(self,name,gender,age):
        self.name=name
        self.gender=gender
        self.age=age
    def sleep(self,time=None):
        self.time=time
        if self.time!=None:
            if self.time>=3 and self.time<=5:
                self.food='Mixed Veggies'
            if self.time>=6 and self.time<=8:
                self.food='Eggplant & Tofu'
            if self.time>=9 and self.time<=11:
                self.food='Broccoli Chicken'
            print('{} sleeps {} hours daily and should have {}'.format(self.name,self.time,self.food))
        else:
            print("{}'s duration is unknown thus should have only bamboo leaves".format(self.name))

panda1=Panda("Kunfu","Male", 5)
panda2=Panda("Pan Pan","Female",3)
panda3=Panda("Ming Ming","Female",8)
print(panda2.sleep(10))
print(panda1.sleep(4))
print(panda3.sleep())

Answer 1

print函数不会在 Python 中返回，它只是写入stdout ； 因此，当您为实例调用sleep方法时，它只会打印None 。

要解决此问题，您必须做的是return而不是在sleep中打印，或者只是调用它而不将其包含在print语句中。

结果是这样的，例如：

class Panda:
    def __init__(self,name,gender,age):
        self.name=name
        self.gender=gender
        self.age=age
    def sleep(self,time=None):
        self.time=time
        if self.time!=None:
            if self.time>=3 and self.time<=5:
                self.food='Mixed Veggies'
            if self.time>=6 and self.time<=8:
                self.food='Eggplant & Tofu'
            if self.time>=9 and self.time<=11:
                self.food='Broccoli Chicken'
            return '{} sleeps {} hours daily and should have {}'.format(self.name,self.time,self.food)
        else:
            return "{}'s duration is unknown thus should have only bamboo leaves".format(self.name)

panda1=Panda("Kunfu","Male", 5)
panda2=Panda("Pan Pan","Female",3)
panda3=Panda("Ming Ming","Female",8)
print(panda2.sleep(10))
print(panda1.sleep(4))
print(panda3.sleep())

或者

class Panda:
    def __init__(self,name,gender,age):
        self.name=name
        self.gender=gender
        self.age=age
    def sleep(self,time=None):
        self.time=time
        if self.time!=None:
            if self.time>=3 and self.time<=5:
                self.food='Mixed Veggies'
            if self.time>=6 and self.time<=8:
                self.food='Eggplant & Tofu'
            if self.time>=9 and self.time<=11:
                self.food='Broccoli Chicken'
            print('{} sleeps {} hours daily and should have {}'.format(self.name,self.time,self.food))
        else:
            print("{}'s duration is unknown thus should have only bamboo leaves".format(self.name))

panda1=Panda("Kunfu","Male", 5)
panda2=Panda("Pan Pan","Female",3)
panda3=Panda("Ming Ming","Female",8)
panda2.sleep(10)
panda1.sleep(4)
panda3.sleep()

Answer 2

所以第一个print语句是由于sleep方法中的print函数。 None正在打印，因为您有print(panda1.sleep()) 。 sleep方法不返回任何内容，因此None 。

要摆脱None ，您可以简单地使用panda1.sleep()而不是print(panda1.sleep()) 。

但是，更好的选择可能是返回您希望sleep函数打印的消息，然后使用print(panda1.sleep())