python基础教程-函数

函数

哈尔滨工业大学计算机学院

叶麟

函数是什么主要内容

1

函数定义与调用2

函数参数与返回值3

变量作用域4

函数优缺点

5

求1 to 10, 20 to 37, 35 to 49的和sum = 0

for i in range(1, 11):

sum += i

print("Sum from 1 to 10 is", sum) sum = 0

for i in range(20, 38):

sum += i

print("Sum from 20 to 37 is", sum) sum = 0

for i in range(35, 50):

sum += i

print("Sum from 35 to 49 is", sum)

def sum(i1, i2):

result = 0

for i in range(i1, i2 + 1):

result += i

return result

def main():

print("Sum from 1 to 10 is", sum(1, 10))

print("Sum from 20 to 37 is", sum(20, 37)) print("Sum from 35 to 49 is", sum(35, 49)) main() # Call the main function

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函数

⏹完成特定功能的一个语句组，这组语句可以作为

一个单位使用，并且给它取一个名字

⏹通过函数名执行

f(x) =

x2–2x + 1

函数头def sum(i1, i2):”””To calculate the sum from i1 to i2i1 is low value, i2 is high value ”””

关键字函数名参数

缩进

说

明

文

函数体result = 0

for i in range(i1, i2 + 1):

result += i

return result #return sum value 档语句

函数定义

形式参数（形参）def sum(i1, i2):

result = 0

for i in range(i1, i2 + 1):

result += i

return result

函数调用

实际参数（实参）sum(1, 10)

def sum(i1, i2):

result = 0

for i in range(i1, i2 + 1):

result += i

return result

def main():

print("Sum from 1 to 10 is", sum(1, 10))

print("Sum from 20 to 37 is", sum(20, 37)) print("Sum from 35 to 49 is", sum(35, 49)) main() # Call the main function

def main():sum(1, 10)

def sum(i1, i2):result = 0for i in range(i1, sum(20, 37)sum(35, 49)main()i2 + 1):result += i

return result

def sum(i1, i2):

result = 0

for i in range(i1, i2 + 1):

result += i

return result

sum(1, 10)

def Biggersmaller(bigger, smaller): print bigger -smaller

Biggersmaller(3, 1)

Biggersmaller(1, 3) Biggersmaller(smaller = 1, bigger = 3)

函数参数–缺省参数

def defaultParameters(arg1, arg2=2, arg3=3): print'arg1=', arg1

print'arg2=', arg2

print'arg3=', arg3

defaultParameters(10)

defaultParameters(10, 10)

defaultParameters(10, 10, 10)

函数返回值

def sum(i1, i2):

result = 0

for i in range(i1, i2 + 1):

result += I

return result

•函数调用完成后，返回数据

•Return语句终止当前函数的执行

•Return后的语句将被忽略

globalVar= 1

def f1():

localVar= 2

print globalVar

print localVar f1()

print globalVar print localVar