TypeError:只能将列表(而不是"int")连接到列表4 [英] TypeError: can only concatenate list (not "int") to list 4

问题描述

我的课程要求使用Python模块，并且我的脚本出现此错误.它在绘制弹丸的轨迹并计算其他一些变量.我已经按照给出的小册子中的内容键入了脚本.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.如果有人可以快速解决我，我将不胜感激，我现在​​没有时间学习足够的知识来自己解决问题.

I'm required to take a Python module for my course and I get this error for my script. It's plotting the trajectory of a projectile and calculating a few other variables. I've typed the script exactly as in the booklet we are given. Because I am an absolute beginner I can't understand other answers to this error. I would appreciate it an awful lot if someone could give me a quick fix, I don't have time at the moment to learn enough to fix it myself.

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))]

错误明确显示:

  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

推荐答案

正如注释中指出的那样，这是令人反感的行

As is pointed out in the comments, this is the offending line

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

在这里，实际上 i 并没有像注释中所暗示的那样增加.当 i 为1时，它将被设置为 [1 + 1] ，其结果为 [2] ，该列表仅包含数字2.卸下支架.

Here, i is not actually being incremented as the comment suggests. When i is 1, it's being set to [1 + 1], which evaluates to [2], the list containing only the number 2. Remove the brackets.

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