python画图函数matplotlib.pyplot

首先导入函数import matplotlib.pyplot as plt

点状图：plt.scatter(x, y) x，y为行坐标数组，列坐标数组。二者长度要一致

设置行距：plt.xticks(np.arange(-5,5,1))，行坐标从-5开始，5结束，坐标间隔为1
设置列距：plt.yticks(np.arange(-5,5,1))，行坐标从-5开始，5结束，坐标间隔为1
注意plt.yticks（）接收参数的也是列表

最后显示图：plt.show()

import matplotlib.pyplot as plt
import numpy as np

x = []
y = []
b1 = [2,3]
b2 = [5,7]
l = 9999#向量长度平方和
res_x1 = 0
res_x2 = 0
for x1 in range(-7,1):#x1测试数据：-7 到0
    for x2 in range(0,4):#x2测试数据:0到3
        x.append(x1 * b1[0] +x2 * b2[0])
        y.append(x1 * b1[1] +x2 * b2[1])
        if x[-1] == 0 and y[-1] == 0 or (x[-1]**2 + y[-1]**2) > 49:#去同时为0情况，同时只取半径为7的圆内的点
            x.pop()
            y.pop()
            continue
        if (x[-1] ** 2 + y[-1] ** 2) < l and (x[-1] != 0 or y[-1] != 0) :
            l = (x[-1] ** 2 + y[-1] ** 2)
            res_x1 = x1 
            res_x2 = x2
plt.scatter(x, y)
plt.xticks(np.arange(-5,5,1))
plt.yticks(np.arange(-5,5,1))
plt.show()
print("x1=",res_x1,"x2=",res_x2)
print("向量和最短长度:",l)