函数:函数是组织好的,可重复使用的,用来实现单一,或相关联功能的代码段。
函数的定义
定是函数使用def关键字
def myfunc(x):
if x >= 0:
return x else:
return -x
空函数
def emptyfunc():
pass
参数检查
def checkfunc(x):
if not isinstance(x,(int,float)):
raise TypeError("must be int or float type!")
if x >= 0:
return x
else:
return -x
返回多个值
def price(x):
apple=x*2
banana=x*2.5
return apple,banana
a,b=price(1)
函数的参数
必选参数parameter
def printdetail1(name,age,telephone):
print("姓名:",name)
print("年龄:",age)
print("电话:",telephone)
printdetail1("Jack",12,12356435678)
默认参数parameter=value
def printdetail2(name,age,telephone,gender='fale'):
print("姓名:",name)
print("性别:",gender)
print("年龄:",age)
print("电话:",telephone)
printdetail2("Jack",12,12356435678,gender='female')
可变参数*
1.不定长传参
def fun1(*number):
for i in number:
print(i)fun1(1,2,3,4,5,6,7,8)
2.元组和列表的压包
def fun2(*number):
s=0
for i in number:
s+=i
print(s)
fun2(*[1,2,3,4,5])
fun2(*(1,2,3,4,5))
关键参数**
使用方法一
def fun(id,name,**kargs):
print("id:",id)
print("name:",name)
print("others:",kargs)
fun(2,"xiaohua",sex="man",age='12')
使用方法二
extra={'sex': 'man', 'age': 12}
def fun(id,name,**kargs):
print("id:",id)
print("name:",name)
print("others:",kargs)
fun(2,"xiaohua",sex=extra['sex'],age=extra['age'])
使用方法三
extra={'sex': 'man', 'age': 12}
def fun(id,name,**kargs):
print("id:",id)
print("name:",name)
print("others:",kargs)
fun(2,"xiaohua",**extra)
关键字参数*
def fun(name,age,*,city,job,completion):
print("name:",name)
print("age:",age)
print("city:",city)
print("job:",job)
print("completion:",completion)
fun('Jack',12,city='shanghai',job='teacher',completion=True)
命名关键字参数需要一个特殊分隔符*,后面的参数被视为命名关键字参数
如果函数定义中已经有了一个可变参数,后面跟着的命名关键字参数就不再需要一个特殊分隔符*了
参数组合
def fun(parameter,*args,keyparameter,**kargs):
print(parameter)
print(args)
print(keyparameter)
print(kargs)
fun(1,*(1,2,3,4),keyparameter=True,**{'id':2})
参数定义的顺序必须是:必选参数、默认参数、可变参数、命名关键字参数和关键字参数
函数的递归
#阶乘计算
def fact(n):
if n == 1:
return 1
return n * fact(n-1)