Python 教程 - 第五部分

函数

• 定义函数
• 示例代码

#无返回值
def sayHelloTo(username):
    print("Hello.%s" % username)
#有1个返回值
def getWelcomeMsg(username):
    msg="Welcome to my tutorial,%s" % username
    return msg
#有多个返回值
def calculateByFourOperations(n1,n2):
    sum=n1+n2
    sub=n1-n2
    multi=n1*n2
    div="Illegal divisor:0"
    if n2!=0 :
        div=n1/n2
    return sum,sub,multi,div

username=input("Please input your name:")
sayHelloTo(username)
welcomeMsg=getWelcomeMsg(username)
print("Welcome msg=%s." % welcomeMsg)
n1Str=input("Please input operation number 1:")
n2Str=input("Please input operation number 2:")
n1=int(n1Str)
n2=int(n2Str)
sum,sub,multi,div=calculateByFourOperations(n1,n2)
print("sum=%d,sub=%d,multi=%d" %(sum,sub,multi))
print("div=",div)

• 练习题
• 题目

请定义一个函数quadratic(a, b, c)，接收3个参数，返回一元二次方程：ax2 + bx + c = 0的两个解。
提示：计算平方根可以调用math.sqrt()函数。

• 解答

import math
def calculateDiv(a,b):
    result="Illegal divisor:0"
    if b!=0 :
        result=a/b
    return result
def quadratic(a,b,c):
    result=[]
    if a==0 :
        return calculateDiv(-c,b)
    else :
        delta=b*b-4*a*c
        if delta<0 :
            pass
        elif delta==0:
            solution1=-b/(2*a)
            result=[solution1]
        else:
            solution1=(-b+math.sqrt(delta))/(2*a)
            solution2=(-b-math.sqrt(delta))/(2*a)
            result=[solution1,solution2]
    return result
a=int(input("Please input a:"))
b=int(input("Please input b:"))
c=int(input("Please input c:"))
result=quadratic(a,b,c)
print("%d^2+%dx+%d=%s" % (a,b,c,result))           

文件读写

• 写文件

f = open('testFileIO.txt', 'w')
f.write("This is the content\n")
f.close()