在这个程序中，我有一个表示一个卷（包含数量和单位）的类。我在运行它时遇到此错误，并且当我在解释器中尝试以下操作时：
class Volume(object):
def __init__ (self, m = 0, u = "ml"):
self.__magnitude = m
self.__units = u
def is_valid (self): #checks if the volume and units are valid
if type(self.__magnitude) == int and type(self.__units) == str:
if self.__units == "ml" or self.__units == "oz":
if self.__magnitude < 0:
return True
else:
return False
else:
return False
else:
return False
def __repr__ (self):
if Volume.is_valid(self):
return str(self.__magnitude) + " " + str(self.__units) #needs fix
def __str__ (self):
if Volume.is_valid(self):
return round(self.__repr__(),3) #fix
def units (self): #returns the units of the volume
if Volume.is_valid(self):
return self.__units
def magnitude (self): #returns the magnitude of the volume
if Volume.is_valid(self):
return self.__magnitude
def metric (self): #transforms the magnitude into metric system if needed
if Volume.is_valid(self):
if self.__units == "ml":
return self.__units
elif self.__units == "oz":
mil = self.__units / 0.033814
return mil
def customary (self): #transforms the magnitude into customary if needed
if Volume.is_valid(self):
if self.__units == "oz":
return self.__units
elif self.__units == "ml":
ozs = self.__units * 0.033814
return ozs
def __add__ (self, v2): #adds to magnitude using an int or another volume
if Volume.is_valid(self):
if isinstance(v2, Volume):
if Volume.is_valid(v2): #check if V2 is valid
if self.__units == v2.__units:
return Volume(self.__magnitude + v2.__magnitude,
self.__units)
else:
if v2.__units == 'ml':
v3 = v2.customary()
return Volume(self.__magnitude + v3.__magnitude,
self.__units)
elif v2.__units == 'oz':
v3 = v2.__units
return Volume(self.__magnitude + v3.__magnitude,
self.__units)
elif isinstance(v2,(int,float)):
#create new Volume with same units as self
v3 = Volume(v2, self.__units)
return Volume(self.__magnitude + v3.__magnitude, self.__units)
def __radd__ (self, v2): #adds ability to do i.e. 2 + a
return self.__add__(v2)
def __sub__ (self, v2): #same as __add__ but this subtracts
if Volume.is_valid(self):
if isinstance(v2, Volume):
if Volume.is_valid(v2):
if self.__units == v2.__units:
return Volume(self.__magnitude - v2.__magnitude,
self.__units)
else:
if v2.__units == 'ml':
v3 = v2.customary()
return Volume(self.__magnitude - v3.__magnitude,
self.__units)
elif v2.__units == 'oz':
v3 = v2.__units
return Volume(self.__magnitude - v3.__magnitude,
self.__units)
elif isinstance(v2,(int,float)):
v3 = Volume(v2, self.__units)
return Volume(self.__magnitude - v3.__magnitude, self.__units)
def __rsub__ (self, v2):
return Volume(v2.__magnitude - self.__magnitude, self.__units)
def __mult__ (self, v2):#multiplies a volume by an int only (not other vol)
if Volume.is_valid(self):
return Volume(self.__magnitude * v2.__magnitude, self.__units)
def __rmult__ (self, v2):
return self.__mult__(v2)
def __eq__ (self, v2): #checks if 2 volumes are equal
if Volume.is_valid(self):
if isinstance(v2, Volume):
if Volume.is_valid(v2):
if self.__units == v2.__units:
return self.__magnitude == v2.__magnitude
else:
if v2.__units == 'ml':
v3 = v2.customary()
return self.__magnitude == v3.__magnitude
elif v2.__units == 'oz':
v3 = v2.__units
return self.__magnitude == v3.__magnitude
elif isinstance(v2,(int,float)):
v3 = Volume(v2, self.__units)
return self.__magnitude == v3.__magnitude
def __noteq__ (self, v2): #checks if 2 volumes are not equal
if Volume.is_valid(self):
if isinstance(v2, Volume):
if Volume.is_valid(v2):
if self.__units == v2.__units:
return self.__magnitude != v2.__magnitude
else:
if v2.__units == 'ml':
v3 = v2.customary()
return self.__magnitude != v3.__magnitude
elif v2.__units == 'oz':
v3 = v2.__units
return self.__magnitude != v3.__magnitude
elif isinstance(v2,(int,float)):
v3 = Volume(v2, self.__units)
return self.__magnitude != v3.__magnitude
def __lt__ (self, v2): #checks if 1 volume is < than the other volume
if Volume.is_valid(self):
if isinstance(v2, Volume):
if Volume.is_valid(v2):
if self.__units == v2.__units:
return self.__magnitude < v2.__magnitude
else:
if v2.__units == 'ml':
v3 = v2.customary()
return self.__magnitude < v3.__magnitude
elif v2.__units == 'oz':
v3 = v2.__units
return self.__magnitude < v3.__magnitude
elif isinstance(v2,(int,float)):
v3 = Volume(v2, self.__units)
return self.__magnitude <= v3.__magnitude
def __gt__ (self, v2): #checks if 1 volume is > than the other volume
if Volume.is_valid(self):
if isinstance(v2, Volume):
if Volume.is_valid(v2):
if self.__units == v2.__units:
return self.__magnitude > v2.__magnitude
else:
if v2.__units == 'ml':
v3 = v2.customary()
return self.__magnitude > v3.__magnitude
elif v2.__units == 'oz':
v3 = v2.__units
return self.__magnitude > v3.__magnitude
elif isinstance(v2,(int,float)):
v3 = Volume(v2, self.__units)
return self.__magnitude > v3.__magnitude
def __lteq__ (self, v2):#checks if 1 volume is <= to other volume
if Volume.is_valid(self):
if isinstance(v2, Volume):
if Volume.is_valid(v2):
if self.__units == v2.__units:
return self.__magnitude <= v2.__magnitude
else:
if v2.__units == 'ml':
v3 = v2.customary()
return self.__magnitude <= v3.__magnitude
elif v2.__units == 'oz':
v3 = v2.__units
return self.__magnitude <= v3.__magnitude
elif isinstance(v2,(int,float)):
v3 = Volume(v2, self.__units)
return self.__magnitude <= v3.__magnitude
def __gteq__ (self, v2):#checks if 1 volume is >= to other volume
if Volume.is_valid(self):
if isinstance(v2, Volume):
if Volume.is_valid(v2):
if self.__units == v2.__units:
return self.__magnitude >= v2.__magnitude
else:
if v2.__units == 'ml':
v3 = v2.customary()
return self.__magnitude >= v3.__magnitude
elif v2.__units == 'oz':
v3 = v2.__units
return self.__magnitude >= v3.__magnitude
elif isinstance(v2,(int,float)):
v3 = Volume(v2, self.__units)
return self.__magnitude >= v3.__magnitude
我需要先修复此错误，然后才能检查其他方法是否有效，但我似乎无法找到解决方法。这是我的代码：
RelativeLayout.LayoutParams adViewParams = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.WRAP_CONTENT,
RelativeLayout.LayoutParams.WRAP_CONTENT);
adViewParams.addRule(RelativeLayout.CENTER_HORIZONTAL | RelativeLayout.ALIGN_PARENT_TOP);
RelativeLayout layout = new RelativeLayout(this);
layout.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT));
AdRequest adRequest = new AdRequest.Builder().addTestDevice(AdRequest.DEVICE_ID_EMULATOR).build();
AdView adView = new AdView(this);
adView.setAdSize(AdSize.BANNER);
adView.setAdUnitId("some id here");
adView.loadAd(adRequest);
layout.addView(adView, adViewParams);
答案 0 :(得分：2)
def __repr__ (self):
if Volume.is_valid(self):
return str(self.__magnitude) + " " + str(self.__units) #needs fix
在此代码中，如果测试为False，则该函数不会返回任何内容（也就是None），因为您没有else关闭。你在不同的方法中有相同的反模式。之一：
else子句以返回合理的值; 关于Volume(10, "ml") - AFAICT，这将根据您的is_valid方法 验证：
def is_valid (self): #checks if the volume and units are valid
if type(self.__magnitude) == int and type(self.__units) == str:
if self.__units == "ml" or self.__units == "oz":
if self.__magnitude < 0:
return True
else:
return False
else:
return False
else:
return False
该方法返回True的唯一方法是以"oz"或"ml"为单位，为负幅度（self.__magnitude < 0 ）。
根据我的理解，你的验证逻辑应该是这样的：
def is_valid (self): #checks if the volume and units are valid
return (self.__units == "ml" or self.__units == "oz") and \
self.__magnitude >= 0;
总之，您不需要调用is_valid作为类方法：
if Volume.is_valid(self):
...
从我看到的，这是一个正确的实例方法，应该像这样调用：
if self.is_valid():
...