Python - Day 14:函数知识应用实例

Python 2020春季学期

语法基础知识: if...else三元表达式:

if x > y:
    a = x
else:
    a = y

上述语句可以简化为:

a = x if x>y else y

Python还支持从列表中挑选对象，其基本格式如下：

a = [x,y][f]   #f为假时将x赋值给a，否则将y赋值给a
c = [b,a][a>b] #c获得 a,b中较大值

函数应用实例：数码管风格的日期显示

例7.1

import turtle, datetime
def drawLine(draw):   #绘制单段数码管
    turtle.pendown() if draw else turtle.penup() #这是if...else三元表达式
    turtle.fd(40)
    turtle.right(90)
def drawDigit(digit): #根据数字绘制七段数码管
    drawLine(True) if digit in ['-',2,3,4,5,6,8,9] else drawLine(False) #这是if...else三元表达式
    drawLine(True) if digit in [0,1,3,4,5,6,7,8,9] else drawLine(False)
    drawLine(True) if digit in [0,2,3,5,6,8,9] else drawLine(False)
    drawLine(True) if digit in [0,2,6,8] else drawLine(False)
    turtle.left(90)
    drawLine(True) if digit in [0,4,5,6,8,9] else drawLine(False)
    drawLine(True) if digit in [0,2,3,5,6,7,8,9] else drawLine(False)
    drawLine(True) if digit in [0,1,2,3,4,7,8,9] else drawLine(False)
    turtle.left(180)
    turtle.penup()
    turtle.fd(20)
def drawDate(date):  #获得要输出的数字
    for i in date:
        if i in "0123456789":
            drawDigit(eval(i))  #注意: 通过eval()函数将数字变为整数 ，也可以用int()
        else:
            drawDigit(i)
def main():
    turtle.setup(800, 350, 200, 200)
    turtle.penup()
    turtle.pencolor("red")
    turtle.fd(-300)
    turtle.pensize(9)
    d = datetime.datetime.now().strftime('%Y-%m-%d')
    drawDate( d )       #调用drawDate(), d为实参, 值传递
    turtle.hideturtle()
main() 

例子7.2: 另一种数码管风格的日期显示

#e7.2SevenSegDisplay.py
import turtle, datetime
def drawGap(): #绘制数码管间隔
    turtle.penup()
    turtle.fd(5)
def drawLine(draw):   #绘制单段数码管
    drawGap()
    turtle.pendown() if draw else turtle.penup()
    turtle.fd(40)
    drawGap()    
    turtle.right(90)
def drawDigit(d): #根据数字绘制七段数码管
    drawLine(True) if d in [2,3,4,5,6,8,9] else drawLine(False)
    drawLine(True) if d in [0,1,3,4,5,6,7,8,9] else drawLine(False)
    drawLine(True) if d in [0,2,3,5,6,8,9] else drawLine(False)
    drawLine(True) if d in [0,2,6,8] else drawLine(False)
    turtle.left(90)
    drawLine(True) if d in [0,4,5,6,8,9] else drawLine(False)
    drawLine(True) if d in [0,2,3,5,6,7,8,9] else drawLine(False)
    drawLine(True) if d in [0,1,2,3,4,7,8,9] else drawLine(False)
    turtle.left(180)
    turtle.penup()
    turtle.fd(20)
def drawDate(date):
    turtle.pencolor("red")
    for i in date:
        if i == '-':
            turtle.write('年',font=("Arial", 30, "normal"))
            turtle.pencolor("green")
            turtle.fd(40) 
        elif i == '=':
            turtle.write('月',font=("Arial", 30, "normal"))
            turtle.pencolor("blue")
            turtle.fd(40)
        elif i == '+':
            turtle.write('日',font=("Arial", 30, "normal"))
        else:
            drawDigit(eval(i))
def main():
    turtle.setup(800, 350, 200, 200)
    turtle.penup()
    turtle.fd(-350)
    turtle.pensize(9)
    drawDate(datetime.datetime.now().strftime('%Y-%m=%d+'))
    turtle.hideturtle()
main()