python - 类型错误:只能将列表(不是 "int")连接到列表 4

Question

我的类(class)需要学习 Python 模块，但我的脚本出现此错误。它绘制射弹的轨迹并计算其他一些变量。我已经按照我们提供的小册子中的内容准确地输入了脚本。 因为我是一个绝对的初学者，所以我无法理解此错误的其他答案。如果有人能给我一个快速解决方案，我将非常感激，我现在​​没有时间学习足够的知识来自己解决它。

代码:

import matplotlib.pyplot as plt
import numpy as np
import math # need math module for trigonometric functions

g = 9.81 #gravitational constant
dt = 1e-3 #integration time step (delta t)
v0 = 40 # initial speed at t = 0

angle = math.pi/4 #math.pi = 3.14, launch angle in radians

time = np.arange(0,10,dt) #time axis
vx0 = math.cos(angle)*v0 # starting velocity along x axis
vy0 = math.sin(angle)*v0 # starting velocity along y axis

xa = vx0*time # compute x coordinates
ya = -0.5*g*time**2 + vy0*time # compute y coordinates

fig1 = plt.figure()
plt.plot(xa, ya) # plot y versus x
plt.xlabel ("x")
plt.ylabel ("y")
plt.ylim(0, 50)
plt.show()

    def traj(angle, v0): # function for trajectory
        vx0 = math.cos(angle) * v0 # for some launch angle and starting  velocity
    vy0 = math.sin(angle) * v0 # compute x and y component of starting velocity

    x = np.zeros(len(time))   #initialise x and y arrays
    y = np.zeros(len(time))

    x[0], y[0], 0 #projecitle starts at 0,0
    x[1], y[1] = x[0] + vx0 * dt, y[0] + vy0 * dt # second elements of x and
                                              # y are determined by initial 
                                              # velocity
    i = 1
    while y[i] >= 0: # conditional loop continuous until
    # projectile hits ground
        x[i+1] = (2 * x[i] - x[i - 1]) # numerical integration to find x[i + 1]                                       
        y[i+1] = (2 * y[i] - y[i - 1]) - g * dt ** 2 # and y[i + 1]

        i = [i + 1] # increment i for next loop


        x = x[0:i+1] # truncate x and y arrays                                                
        y = y[0:i+1]
        return x, y, (dt*i), x[i] # return x, y, flight time, range of projectile

x, y, duration, distance = traj(angle, v0)
print "Distance:" ,distance
print "Duration:" ,duration

n = 5
angles = np.linspace(0, math.pi/2, n)
maxrange = np.zeros(n)

for i in range(n):
    x,y, duration, maxrange [i] = traj(angles[i], v0)

angles = angles/2/math.pi*360 #convert rad to degress

print "Optimum angle:", angles[np.where(maxrange==np.max(maxrange))]

明确的错误:

  File "C:/Users/***** at *****", line 52, in traj
    x = x[0:i+1] # truncate x and y arrays

TypeError: can only concatenate list (not "int") to list

Answer 1

正如评论中所指出的，这是有问题的行

i = [i + 1] # increment i for next loop

这里，i 实际上并没有像评论所暗示的那样递增。当 i 为 1 时，它被设置为 [1 + 1]，其计算结果为 [2]，即仅包含数字 2 的列表.去掉括号。