Python练手例子（11）

61、打印出杨辉三角形。

#python3.7
from sys import stdout

if __name__ == '__main__':
    a = []
    for i in range(10):
        a.append([])
        for j in range(10):
            a[i].append(0)
    for i in range(10):
        a[i][0] = 1
        a[i][i] = 1
    for i in range(2,10):
        for j in range(1,i):
            a[i][j] = a[i - 1][j-1] + a[i - 1][j]
    for i in range(10):
        for j in range(i + 1):
            stdout.write(str(a[i][j]))
            stdout.write(' ')
        print()

62、查找字符串。

#python3.7

sStr1 = 'language'
sStr2 = 'age'
print(sStr1.find(sStr2))

结果：
5

63、使用Tkinter画椭圆。

#python3.7
from tkinter import *

if __name__ == '__main__':
    x = 360
    y = 160
    top = y - 30
    bottom = y - 30

    canvas = Canvas(width = 400, height = 600, bg = 'white')
    for i in range(20):
        canvas.create_oval(250 - top, 250 - bottom, 250 + top, 250 + bottom)
        top -= 5
        bottom += 5
    canvas.pack()
    mainloop()

64、利用ellipse 和 rectangle 画图。

#python3.7
from tkinter import *

if __name__ == '__main__':
    canvas = Canvas(width = 400, height = 600, bg = 'white')
    left = 20
    right = 50
    top = 50
    num = 15
    for i in range(num):
        canvas.create_oval(250 - right, 250 - left, 250 + right, 250 + left)
        canvas.create_oval(250 - 20, 250 - top, 250 + 20, 250 + top)
        canvas.create_oval(20 - 2 * i, 20 - 2 * i, 10 * (i + 2), 10 * (i + 2))
        right += 5
        left += 5
        top += 10

    canvas.pack()
    mainloop()

65、一个最优美的图案。

#python3.7
from tkinter import *
import math

class PTS:
    def __init__(self):
        self.x = 0
        self.y = 0
points = []

def LineToDemo():
    screenx = 400
    screeny = 400
    canvas = Canvas(width = screenx, height = screeny, bg = 'white')

    AspectRatio = 0.85
    MAXPTS = 15
    h = screeny
    w = screenx
    xcenter = w / 2
    ycenter = h / 2
    radius = (h - 30) / (AspectRatio * 2) - 20
    step = 360 / MAXPTS
    angle = 0.0
    for i in range(MAXPTS):
        rads = angle * math.pi / 180.0
        p = PTS()
        p.x = xcenter + int(math.cos(rads) * radius)
        p.y = ycenter - int(math.sin(rads) * radius * AspectRatio)
        angle += step
        points.append(p)
    canvas.create_oval(xcenter - radius, ycenter - radius,
                       xcenter + radius, ycenter + radius)
    for i in range(MAXPTS):
        for j in range(i, MAXPTS):
            canvas.create_line(points[i].x, points[i].y, points[j].x,points[j].y)

    canvas.pack()
    mainloop()

if __name__ == '__main__':
    LineToDemo()

66、输入3个数a,b,c，按大小顺序输出。

#python3.7

if __name__ == '__main__':
    n1 = int(input('n1 = \n'))
    n2 = int(input('n2 = \n'))
    n3 = int(input('n3 = \n'))

    def swap(p1, p2):
        return p2, p1

    if n1 > n2: n1, n2 = swap(n1, n2)
    if n1 > n2: n1, n3 = swap(n1, n3)
    if n2 > n3: n2, n3 = swap(n2, n3)

    print(n1, n2, n3)

参考资料：

Python 100例