如何修复'Type Error:unsuppored operand type(s) for +：'int‘and 'list’‘

Question

from random import choice


class RandomWalk():

     """a class generates random datas"""
    def __init__(self, num_points=5000):

        self.num_points = num_points
        self.x_values = [0]
        self.y_values = [0]


    def fill_walk(self):
        """caculate all points generated by RandomWalk """
        while len(self.x_values) < self.num_points:
            #decide the direction and distance
            x_direction = choice([1,-1])
            x_distance = choice([0, 1, 2, 3, 4])
            x_step = x_direction * x_distance
            #the same with x
            y_direction = choice([1, -1])
            y_distance = ([0, 1, 2, 3, 4])
            y_step = y_direction * y_distance

            if x_step == 0 and y_step ==0:
                continue

            #caculate next_x and next_y    
            next_x = self.x_values[-1] + x_step
            next_y = self.y_values[-1] + y_step



            self.x_values.append(next_x)
            self.y_values.append(next_y)


rw_visual.py

以下是代码

import matplotlib.pyplot as plt
from random_walk import RandomWalk
#generate a instance named RandomWalk, paint all included points
rw = RandomWalk()
rw.fill_walk()
plt.scatter(rw.x_values, rw.y_values, s=15)
plt.show()

The result showed that random_walk.py", line 26, in fill_walk
    next_y = self.y_values[-1] + y_step
TypeError: unsupported operand type(s) for +: 'int' and 'list'`

Answer 1

当您绑定到next_x = self.x_values[-1] + x_step时，self.x_values[-1]是int类型，而x_step是一个列表。

您遗漏了choice，所以程序将y_distance视为一个列表。在python中，将列表与int相乘是完全合法的，因此您最终会将y_step设置为[0*y_distance, 1*y_distance, 2*y_distance, 3*y_distance, 4*y_distance]。所以当你去添加y_step时，它的类型是list。

#decide the direction and distance
x_direction = choice([1,-1])
x_distance = choice([0, 1, 2, 3, 4])
x_step = x_direction * x_distance
#the same with y
y_direction = choice([1, -1])
y_distance = ([0, 1, 2, 3, 4]) # Here you left out choice
y_step = y_direction * y_distance

因此，当程序遇到错误时，它试图

next_y = self.y_values[-1] + [0*y_distance, 1*y_distance, 2*y_distance, 3*y_distance, 4*y_distance]

这导致了一个错误，因为您不能在Python中将整数添加到列表中。这就解释了你的错误。

类的新代码：

from random import choice 

class RandomWalk():
    """a class that generates random data"""
    def __init__(self, num_points=5000):
        self.num_points = num_points
        self.x_values = [0]
        self.y_values = [0]

    def fill_walk(self):
        """calculate all points generated by RandomWalk """
        while len(self.x_values) < self.num_points:
            #decide the direction and distance
            x_direction = choice([1,-1])
            x_distance = choice([0, 1, 2, 3, 4])
            x_step = x_direction * x_distance
            #the same with y
            y_direction = choice([1, -1])
            y_distance = ([0, 1, 2, 3, 4])
            y_step = y_direction * y_distance

            if x_step == 0 and y_step ==0:
                continue

            #calculate next_x and next_y    
            next_x = self.x_values[-1] + x_step
            next_y = self.y_values[-1] + y_step

            self.x_values.append(next_x)
            self.y_values.append(next_y)

另外，如果你想给人留下深刻印象：

数据可以是复数，也可以是单数。数据的单数是datum；总是单数。例如，“有多少数据?先生，只返回一个数据。”

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