1、
>>> def a(first,middle,last): ## 函数定义了三个形参
full = f"{first} {middle} {last}"
return full.title()
>>> name = a("aaa","bbb","ccc")
>>> print(name)
Aaa Bbb Ccc
>>> name = a("aaa","ccc") ## 当给与两个实参时报错
Traceback (most recent call last):
File "<pyshell#493>", line 1, in <module>
name = a("aaa","ccc")
TypeError: a() missing 1 required positional argument: 'last'
2、
>>> def a(first,last,meddle = ""): ## 将可选参数在定义为默认参数,赋值为空
if meddle:
full = f"{first} {meddle} {last}"
else:
full = f"{first} {last}"
return full
>>> name = a("aaa","ccc","bbb") ## 使用位置参数
>>> print(name)
aaa bbb ccc
>>> name = a("aaa","ccc") ## 省略掉实参 meddle,函数仍然可以调用
>>> print(name)
aaa ccc
将可选实参定义为默认参数空,通使用条件判断实现实参可选。