使用matplotlib绘制圆时出错

您需要使用“从轴添加艺术家”,以下是获取当前轴的最快方法 plt.gcf ,获取当前数字,以及 get_gca ,获取当前轴,我也建议 plt.axis('equal') 绘制圆与椭圆:

import numpy as np
import matplotlib.pyplot as plt 
import matplotlib as mpl

x_gal = np.random.rand(20)
y_gal = np.random.rand(20)

x_rand = np.random.rand(5*20) 
y_rand = np.random.rand(5*20)

plt.figure(1)
plt.plot( x_gal, y_gal, ls=' ', marker='o', markersize=5, color='r' )
plt.plot( 0.5, 0.5, ls=' ', marker='o', markersize=5, color='r' )
plt.plot( x_rand, y_rand, ls=' ', marker='o', markersize=5, color='b' )
plt.axis('off')
plt.axis('equal')

circle1 = plt.Circle((0.5, 0.5), 0.2, color='r', alpha=0.5)
plt.gcf().gca().add_artist(circle1)

plt.tight_layout()
plt.show()

你需要在坐标轴上绘图。

import numpy as np
import matplotlib.pyplot as plt 

x_gal = np.random.rand(20)
y_gal = np.random.rand(20)

x_rand = np.random.rand(5*20) 
y_rand = np.random.rand(5*20)

fig = plt.figure(1)
ax = fig.add_subplot(111)
ax.plot( x_gal, y_gal, ls=' ', marker='o', markersize=5, color='r' )
ax.plot( 0.5, 0.5, ls=' ', marker='o', markersize=5, color='r' )
ax.plot( x_rand, y_rand, ls=' ', marker='o', markersize=5, color='b' )
ax.axis('off')

circle1 = plt.Circle((0.5, 0.5), 0.2, color='r', alpha=0.5)
ax.add_artist(circle1)

plt.tight_layout()
plt.show()

输出: