Method one generates a circle: 

Method 2 generates circles:

Here we are using [matplotlib] generated, but I use the Chinese title, so I need to add two sentences separately:

plt.rcParams['font.sans-serif'] = ['SimHei']  # 用来正常显示中文标签
plt.rcParams['axes.unicode_minus'] = False  # 用来正常显示负号

With these two sentences, we can display it on the panel normally when we display it. 

We use axis('equal') to make the axial x-axis and y-axis equal, so as to draw a better circle.

axis('equal')

The following is how we draw a circle with r=2 as the radius and a,b=(0.,0.) as the center coordinates. I have used two methods for calculation here, which are relatively easy, but One is drawn using con and sin, and the second is drawn using sqrt square root . In the process, we should pay attention that all variables are floating point numbers. If only integer calculations are performed in unit coordinates It is difficult to draw a better-looking circle.

import numpy as np
import matplotlib.pyplot as plt
 
plt.rcParams['font.sans-serif'] = ['SimHei']  # 用来正常显示中文标签
plt.rcParams['axes.unicode_minus'] = False  # 用来正常显示负号
# ==========================================
# 圆的基本信息
# 1.圆半径
r = 2.0
# 2.圆心坐标
a, b = (0., 0.)
# ==========================================
# 方法一：参数方程
theta = np.arange(0, 2 * np.pi, 0.01)
x = a + r * np.cos(theta)
y = b + r * np.sin(theta)
fig = plt.figure()
axes = fig.add_subplot(111)
axes.plot(x, y)
axes.axis('equal')
plt.title('圆形绘制1')
# ==========================================
# 方法二：标准方程
x = np.arange(a - r, a + r, 0.01)
y = b + np.sqrt(r ** 2 - (x - a) ** 2)
fig = plt.figure()
axes = fig.add_subplot(111)
axes.plot(x, y)  # 上半部
axes.plot(x, -y)  # 下半部
plt.axis('equal')
plt.title('圆形绘制2')
# ==========================================
plt.show()

In fact, the simplest circle has to look at the following: here we use turtle , directly use the function color it brings to set the color, circle is to set the radius of the circle, and finally display it. Very happy.

import turtle
 
turtle.color('red')
 
turtle.circle(120)
 
turtle.done()

This circle is equivalent to the process of hand-painting. The effect is still very good. 

Turtle module for Python drawing:

In the "National Youth Software Programming Level Examination" organized by the Chinese Institute of Electronics, candidates are required to know the functions of the turtle library , know how to import the library file, and master its use methods: forward, backward, left and right, lifting the pen, Draw dots, circles, etc.

turtle, Chinese is sea turtle, so we sometimes call it sea turtle drawing.

Turtle module drawing ideas

1. First import the turtle module;
2. The initial default position is set at (0,0), which is the center of the window (the initial position can be set), and the drawing direction is from left to right;
3. The turtle module simulates drawing graphics with a pen. The default pen is downward (turtle.pendown()), as if the pen tip is placed on paper;
4. When starting to draw, set the pen down and move the drawing as required.
5. After drawing, raise the pen turtle.penup()