我将如何允许用户指定坐标数？

Question

如何根据用户想要的数量创建变量（由一开始的简单问题定义）？

import random as ran
from random import *
import matplotlib
import matplotlib.pyplot as plt

coordonei = ran.randint(0,15)
coordoneii = ran.randint(0,15)

coordtwoi = ran.randint(coordonei, coordonei + 5)
coordtwoii = ran.randint(coordoneii, coordoneii + 5)

coordthreei = ran.randint(coordtwoi, coordtwoi + 5)
coordthreeii = ran.randint(coordtwoii, coordtwoii + 5) 

print("(",coordonei,",",coordoneii,")",
"(",coordtwoi,",",coordtwoii,")",
"(",coordthreei,",",coordthreeii,")")

plt.xlim(0, 20)
plt.ylim(0, 20)
plt.xlabel("X Axis")
plt.ylabel("Y Axis")

x_values = [coordonei, coordtwoi, coordthreei]
y_values = [coordoneii, coordtwoii, coordthreeii]
plt.plot(x_values, y_values)

plt.plot(coordonei, coordoneii, '.r-')
plt.plot(coordtwoi, coordtwoii, '.r-')
plt.plot(coordthreei, coordthreeii, '.r-')

plt.show()

这个简单的代码每次只生成一个完整的随机折线图。我希望能够选择该图中有多少个坐标。

Answer 1

这是一个相当干净和简单的解决方案，和你做的一样，但更pythonic：

from random import randint
import matplotlib.pyplot as plt

# n can be any number of course
n = 10

# start a list of tuples with a first tuple of coordinates (x, y)
cs = [(randint(0, 15), randint(0, 15))]
# create n-1 more of them after it
for __ in range(n - 1):
    # cs[-1] is the last tuple in the list, so cs[-1][0] is the x of that tuple
    cs.append((randint(cs[-1][0], cs[-1][0] + 5), randint(cs[-1][1], cs[-1][1] + 5)))

# these are handy for plotting, see below for nicer solution
x_values = [x for x, __ in cs]
y_values = [y for __, y in cs]


# the limits of the plot will be set to 3 beyond the maximum values
plt.xlim(0, max(x_values)+3)
plt.ylim(0, max(y_values)+3)
plt.xlabel("X Axis")
plt.ylabel("Y Axis")

plt.plot(x_values, y_values)

# add the marks
for x, y in cs:
    plt.plot(x, y, '.r-')

plt.show()

如果你问我，那就更好了：

from random import randint
import matplotlib.pyplot as plt

n = 10

cs = [(randint(0, 15), randint(0, 15))]
for __ in range(n - 1):
    # I changed this for readability, doesn't even need a comment
    cx, cy = cs[-1]
    cs.append((randint(cx, cx + 5), randint(cy, cy + 5)))

plt.xlim(0, max(x for x, __ in cs)+3)
plt.ylim(0, max(y for __, y in cs)+3)
plt.xlabel("X Axis")
plt.ylabel("Y Axis")

# this zips up all the tuples into a tuple of lists of x's and y's 
# and then unpacks that tuple 
plt.plot(*zip(*cs))

# add the marks
for x, y in cs:
    plt.plot(x, y, '.r-')

plt.show()

我认为这更好，因为它避免了创建数据的副本，将所有坐标保存在一个漂亮而简单的 x 和 y 对（元组）列表中。所有操作仅引用该列表cs，这意味着它可能非常长，并且您的脚本仍然可以快速运行并且不会浪费空间（或引入意外更改一个副本但忘记另一个副本的机会）。

啊，要完成你的问题的答案，你要开始：

n = int(input('Any positive number:'))

如果您想查看数据在图表中的最终位置：

for i, (x, y) in enumerate(cs):
    plt.annotate(f'{i}:{(x, y)}', xy=(x, y), xytext=(x + 1, y - .5))

Answer 2

您可以为它们使用一个列表，就像您使用 x_values 和 y_values 一样

然后你可以像这样向用户询问坐标：

number = input("How many coordinates do you want to create? ")
number = int(number)

x_values = []
y_values = []

while number:
    cor = input("Enter coordinate (x y): ")
    x, y = cor.split(" ")
    print("(" + str(x) + ", " + str(y) + ")")

    x_values.append(x)
    y_values.append(y)
    number -= 1

最后你可以重新设计最后一部分，使用 for 循环来实现函数：

plt.plot(x_values, y_values)

for x, y in zip(x_values, y_values):
    plt.plot(x, y, '.r-')

完整的代码如下所示：

import random as ran
from random import *
import matplotlib
import matplotlib.pyplot as plt

number = input("How many coordinates do you want to create? ")
number = int(number)

x_values = []
y_values = []

while number:
    cor = input("Enter coordinate (x y): ")
    x, y = cor.split(" ")
    print("(" + str(x) + ", " + str(y) + ")")

    x_values.append(x)
    y_values.append(y)
    number -= 1

plt.xlim(0, 20)
plt.ylim(0, 20)
plt.xlabel("X Axis")
plt.ylabel("Y Axis")

plt.plot(x_values, y_values)

for x, y in zip(x_values, y_values):
    plt.plot(x, y, '.r-')

plt.show()

Answer 3

您可以将它们存储在列表中：

numVar = input('How many variables?')
numVar = int(numVar)

myVars = [ varFunc() for i in range(numVar)] #varFunc would be a function that returns random variables in your case.
    

Answer 4

成分

分解成3个成分（功能）：

1. 通过input从用户那里读取int的坐标数
2. 实现一个返回元组列表的generate_random_coords(num) 函数 - 一对(x,y) 代表一个坐标
3. 将坐标传递给自定义绘图函数

另见：

• How can I read inputs as numbers?
• Read user input numbers and perform a calculation in Python、input 作为int 或str（Python 2 VS Python 3）
• Random 2D coordinates generation
• How do I plot list of tuples in Python?
• Minimum value on a 2d array python
• Finding the Max value in a two dimensional Array
• What does the star and doublestar operator mean in a function call?
• What does python zip(*X) do with "*"(asterisk)?
• 真正的 Python：Using the Python zip() Function for Parallel Iteration

大纲

from random import randint
import matplotlib.pyplot as plt

# define the 3 ingredients (functions)

if __name__ == '__main__':
    num_coords = read_num_coords()
    coords = generate_random_coords(num_coords)
    print(coords)
    plot(coords)

配方

def read_num_coords():
    return int(input("Please enter number of coordinates to plot (e.g. 3):"))


def generate_random_coords(num_coords):
    coords = []
    for i in range(num_coords):
        add = 5 * (i+1)   # starts with 5, then increases by 5
        (prev_x, prev_y) = coords[i-1] if i > 0 else (0,0)  # more than previous 
        x = randint(prev_x, 10+add)
        y = randint(prev_y, 10+add)
        coords.append((x,y))
    return coords


def plot(coords):
    max_x = max([c[0] for c in coords])  # maximum of x values
    plt.xlim(0, max_x+5)  # fix min: 0, max: add 5 more
    plt.xlabel("X Axis")
    max_y = max([c[1] for c in coords])  # maximum of y values
    plt.ylim(0, max_y+5)  # fix min: 0, max: add 5 more
    plt.ylabel("Y Axis")

    plt.plot(*zip(*coords))
    plt.plot(*zip(*coords), '.r-')

    plt.show()

奖励：坐标生成器

简短但有用的answer of Ryan Fu 启发了使用generator 函数。像range(n) 这样可以返回一个迭代器来构建一个list 的坐标。

以下生成器函数可用于列表理解（如[i in range(3)]）和生成器表达式（如i in range(3)） ：

def random_coordinates(count, max_x, max_y):
        x = randint(0, max_x)
        y = randint(0, max_y)
        yield (x,y)

使用coords = [c for c in random_coordinates(num_coords, 20, 10)] 作为上述代码配方中coords = generate_random_coords(num_coords) 的替代品。

注意：虽然之前的 list-factory generate_random_coords 使用前一个坐标作为下一个使用步长 5 的偏移量，但此生成器不跟踪间距。相反，我们使用从 (0,0) 到 (max_x, max_y) 的完整区域来随机生成坐标。

现在我们使用参数 max_x = 20 和 max_y = 10 显式预定义绘图的 x 和 y 轴的最大值。