Python练手例子（10）

55、学习使用按位取反~。

程序分析：~0=1; ~1=0; 
(1)先使a右移4位。 
(2)设置一个低4位全为1,其余全为0的数。可用~(~0<<4) 
(3)将上面二者进行&运算。

#python3.7

if __name__ == '__main__':
    a = 234
    b = ~a
    print('The a\'s 1 complement is %d' % b)
    a = ~a
    print('The a\'s 2 complement is %d' % a)

56、画图，学用circle画圆形。

#python3.7
from tkinter import *

if __name__ == '__main__':

    canvas = Canvas(width = 800, height = 600, bg = 'purple')
    canvas.pack(expand = YES, fill = BOTH)
    k = 1
    j = 1
    for i in range(0, 26):
        canvas.create_oval(310 - k, 250 - k, 310 + k, 250 + k, width = 1)
        k += 1
        j += 0.3

    mainloop()

57、画图，学用line画直线。

#python3.7
from tkinter import *

if __name__ == '__main__':
    canvas = Canvas(width=300, height=300, bg='gold')
    canvas.pack(expand=YES, fill=BOTH)
    x0 = 263
    y0 = 263
    x1 = 275
    y1 = 275
    for i in range(19):
        canvas.create_line(x0, y0, x1, y1, width=1, fill='red')
        x0 = x0 - 5
        y0 = y0 - 5
        x1 = x1 + 5
        y1 = y1 + 5

    x0 = 263
    y0 = 263
    y1 = 275
    for i in range(21):
        canvas.create_line(x0, y0, x0, y1, fill='red')
        x0 += 5
        y0 += 5
        y1 += 5

    mainloop()

58、画图，学用rectangle画方形。　　　

程序分析：rectangle(int left, int top, int right, int bottom)

参数说明：(left ，top )为矩形的左上坐标，(right,bottom)为矩形的右下坐标，两者可确定一个矩形的大小。

#python3.7
from tkinter import *

if __name__ == '__main__':
    root = Tk()
    root.title('Canvas')
    canvas = Canvas(root, width = 400, height = 400, bg = 'yellow')
    x0 = 263
    y0 = 263
    x1 = 275
    y1 = 275
    for i in range(19):
        canvas.create_rectangle(x0, y0, x1, y1)
        x0 -= 5
        y0 -= 5
        x1 += 5
        y1 += 5

    canvas.pack()
    root.mainloop()

59、画图，综合例子。　　

程序分析：利用for循环控制100-999个数，每个数分解出个位，十位，百位。

#python3.7
from tkinter import *
import math

if __name__ == '__main__':
    canvas = Canvas(width = 300, height = 300, bg = 'green')
    canvas.pack(expand = YES, fill = BOTH)
    x0 = 150
    y0 = 100
    canvas.create_oval(x0 - 10, y0 - 10, x0 + 10, y0 + 10)
    canvas.create_oval(x0 - 20, y0 - 20, x0 + 20, y0 + 20)
    canvas.create_oval(x0 - 50, y0 - 50, x0 + 50, y0 + 50)
    B = 0.809
    for i in range(16):
        a = 2 * math.pi / 16
        x = math.ceil(x0 + 48 * math.cos(a))
        y = math.ceil(y0 + 48 * math.sin(a) * B)
        canvas.create_line(x0, y0, x, y, fill = 'red')
    canvas.create_oval(x0 - 60, y0 - 60, x0 + 60, y0 + 60)

    for k in range(501):
        for i in range(17):
            a = (2 * math.pi / 16) * i + (2 * math.pi / 180) * k
            x = math.ceil(x0 + 48 * math.cos(a))
            y = math.ceil(y0 + 48 + math.sin(a) * B)
            canvas.create_line(x0, y0, x, y, fill = 'red')
        for j in range(51):
            a = (2 * math.pi / 16) * i + (2 * math.pi / 180) * k - 1
            x = math.ceil(x0 + 48 * math.cos(a))
            y = math.ceil(y0 + 48 * math.sin(a) * B)
            canvas.create_line(x0, y0, x, y, fill = 'red')
    mainloop()

60、计算字符串长度。

#python3.7

sStr1 = 'strlen'
print(len(sStr1))

参考资料：

1、Python 100例

2、python3图形界面简单案例（tkinter）：https://blog.csdn.net/lyhdream/article/details/17514431