python-'NoneType'对象没有属性

Question

I'm new with Python/programming and trying to solve little problems to get a hang of it. I've been struggling with the error below and not too sure how i got it. I understand it is saying the file type is None which is why it's throwing the error. However, I don't get how it is None in the first place? Just wondering if I could get some guidance or hint on the issue? Thank you very much, sorry if the code is messy

line 138, in move self.ecoList[self.temP].nP = tempAni.p AttributeError: 'NoneType' object has no attribute 'nP'

    from random import randint
class Bears:
  def __init__(self):
    self.p = 0
    self.dp = 0
    self.nP = 0
    self.check = True

  def run(self):
    self.dp = randint(-1, 1)
    self.nP = self.dp + self.p
    self.check = False
  def __str__(self):
    return "Bear_"
  def __repr__(self):
    return self.__str__()
class Fish:
  def __init__(self):
    self.p = 0
    self.dp = 0
    self.nP = 0
    self.check = True

  def run(self):
    self.dp = randint(-1, 1)
    self.nP = self.dp + self.p
    self.check = False
  def __str__(self):
    return "Fish|"
  def __repr__(self):
    return self.__str__()
class EcoSystem:
  def __init__(self):
    self.ecoList = [None] * 10
    self.bearList = []
    self.fishList = []

    for i in range(2):
        self.bearList.append(Bears())
        #Adding bear to ecoList
        while True:
            index = randint(0, 9)
            if self.ecoList[index] is None:
                self.ecoList[index] = self.bearList[i]
                self.ecoList[index].p = index
                break
            else:
                continue
    for i in range(2):
        self.fishList.append(Fish())
        #Adding fish to ecoList
        while True:
            index = randint(0, 9)
            if self.ecoList[index] is None:
                self.ecoList[index] = self.fishList[i]
                self.ecoList[index].p = index
                break
            else:
                continue

    self.move()

  def move(self):
    #Print out the current eco system

    print(*self.ecoList, sep='\n')
    anwser = True
    while anwser:


        #populate next move new position for each object
        for i in range(len(self.ecoList)):
            if self.ecoList[i] is None:
                continue
            else:
                self.ecoList[i].run()
        #run for loop to test next position of the object
        for i in range (len(self.ecoList)):
            #if [i] item is None skip to next loop
            if self.ecoList[i] is None:
                continue
            elif self.ecoList[i].check == True:
                continue
            #else check if it is going to move then check adjacent slot is going to be taken
            else:
                tempAni = None #temp animal to compare with item in loop
                #call out new position from item i
                newP = self.ecoList[i].nP
                #call out direction:
                newDP = self.ecoList[i].dp
                #do nothing, skip to next slot if it is not going to move
                if newDP == 0:
                    self.ecoList[i].check = True
                    continue
                elif newDP != 0:#test if new position is going to be out of bound
                    if newP < 0 or newP > (len(self.ecoList)-1):
                        #set new position back to current
                        self.ecoList[i].nP = self.ecoList[i].p
                        self.ecoList[i].dp = 0
                        self.ecoList[i].check = True
                    else:
                        #test if new position is going to be collided
                        if self.ecoList[newP] is not None:
                            if self.ecoList[newP].nP == self.ecoList[i].nP:
                                print("////////////////")
                                tempAni = self.ecoList[newP]
                            #test if the next next new position is not None or out of bound
                            #Assumption - prioritize the closet animal going to move
                            elif (newP+newDP) > 0 and (newP+newDP) < (len(self.ecoList)-1):
                                if self.ecoList[newP+newDP] is not None:
                                    #test if this is going to be collided
                                    if self.ecoList[newP+newDP].nP == self.ecoList[i].nP:
                                        print("\\\\\\\\\\\\\\")
                                        tempAni = self.ecoList[newP+newDP]
                #if tempAni is not none compare the type
                if tempAni is not None:
                    print ("####")
                    print (self.ecoList[i].p)
                    print (self.ecoList[i])
                    print("-----------")
                    print (tempAni.p)
                    print(tempAni)
                    print ("####")
                    #test if they are the same type
                    self.temP = tempAni.p
                    if tempAni.__class__.__name__ == self.ecoList[i].__class__.__name__:
                        #if they are, change new position to current position
                        self.ecoList[i].nP = self.ecoList[i].p
                        self.ecoList[i].check = True
                        print("?????")
                        print(self.temP)
                        print(tempAni)
                        print(tempAni.dp)
                        print(self.ecoList[i])
                        print(self.ecoList[i].dp)
                        self.ecoList[self.temP].nP = tempAni.p
                        self.ecoList[self.temP].check = True
                        #create new animal of the same type and put it to a random place on the list
                        #Assumption - if the list is full add do nothing
                        #Determine tempAni type to create new bear or fish
                        if isinstance(tempAni, Bears):
                            #create new bear
                            newAni = Bears()
                        else:
                            #creaete new fish
                            newAni = Fish()
                        #while loop if the list is still have available spot add new animal to random spot, otherwise do nothing
                        while None in self.ecoList:

                            index = randint(0, 9)
                            if self.ecoList[index] is None:
                                self.ecoList.insert(index, newAni)
                                self.ecoList[index].p = index
                                print ("*****")
                                print (self.ecoList[index].p)
                                print (self.ecoList[index])
                                print ("*****")
                                break
                    #if they are not the same type, kill the fish
                    else:
                        #determine if tempAni is the fish or bear
                        if isinstance(tempAni, Bears):
                            #if it is bears kill the fish in i
                            self.ecoList[i].p = -1
                            self.ecoList[i].check = True
                            self.ecoList[self.temP].check = True
                        elif isinstance(tempAni, Fish):
                            #if it is fish kill it
                            self.ecoList[self.temP].p = -1
                            self.ecoList[i].check = True
                            self.ecoList[self.temP].check = True

        #Apply the change after all the checks are finished
        #Remove all the fish got killed and apply the moves
        for i in range (len(self.ecoList)):
            if self.ecoList[i] is not None:

                    if self.ecoList[i].p == -1:
                        self.ecoList[i] = None
                    elif self.ecoList[i].check == False:
                        self.ecoList[i].check = True
                        newP = self.ecoList[i].nP
                        if newP != i:
                            self.ecoList[newP] = self.ecoList[i]
                            self.ecoList[newP].p = newP
                            self.ecoList[i] = None

        #Print out the current eco system
        print ("---------------------------------------")
        for i in range (len(self.ecoList)):
            print(self.ecoList[i])
            print(i)
        #Ask if user want to continue playing
        test = True
        while test == True:
            strAns = input ('Enter y/n to continue or not: ')
            if strAns.lower() == "n":
                anwser = False
                test = False
                break
            elif strAns.lower() == "y":
                test = False
                break
def main():
EcoSystem()

main()

Answer 1

The error means that self.ecoList[self.temP] is None , although your code does not expect it to be None . So, this is the offending line:

self.ecoList[self.temP].nP = tempAni.p

Your code actually wants to assign tempAni.p to None.nP . None does not have such an attribute, and that is why you get the error. The line where the code throws the exception is just an indication that something is wrong in your code, somewhere . Finding this bug is your task now.

You need to breathe calmly and step-by-step figure out where your code is wrong. This might be anywhere and nobody here on SO will find this for you. Add print and/or assert statements to your code, and narrow down the issue. This is debugging work, and you have to go through it!