11个案例讲透Python函数参数小结

def func(a,b,c=0, d=1):  
    pass  

def func(a,b,c=0, d=1):  
    pass  
  
  # 关键字参数传参方法  
func(a=10, c=30, b=20, d=40)  
  
  # 位置参数传参方法  
func(10, 20, 30, 40)  

def func(*args, **kw):  
    print(args)  
    print(kw)  
  
func(10, 20, c=20, d=40)  

>>> def demo_func(a):  
...     print(a)  
...   
>>> demo_func(10)   
10  
>>> demo_func()  # 不指定会报错  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
TypeError: demo_func() missing 1 required positional argument: 'a'  

>>> def demo_func(b=10):  
...     print(b)  
...   
>>> demo_func(20)  
20  
>>> demo_func()  
10  

>>> def print_profile(name, age):  
...     return f"我的名字叫{name}，今年{age}岁了"  
...  
>>> print_profile("iswbm", 27)  
'我的名字叫iswbm，今年27岁了'  

>>> print_profile(age=27, name="iswbm")  
'我的名字叫iswbm，今年27岁了'  

>>> def demo_func(*args):  
...     print(args)  
...   
>>>   
>>> demo_func(10, 20, 30)  
(10, 20, 30)  

>>> def demo_func(**kw):  
...     print(kw)  
...   
>>> demo_func(a=10, b=20, c=30)  
{'a': 10, 'b': 20, 'c': 30}  

>>> def demo_func(a=1, b):  
...     print(a, b)  
...   
  File "<stdin>", line 1  
SyntaxError: non-default argument follows default argument  
>>>  
>>> def demo_func(a, b=1):  
...     print(a, b)  
...   
>>>  

>>> def demo_func(**kw, *args):  
  File "<stdin>", line 1  
    def demo_func(**kw, *args):  
                        ^  
SyntaxError: invalid syntax  
>>>   
>>> def demo_func(*args, **kw):  
...     print(args, kw)  
...   
>>> 

>>> def demo_func(*args, b):  
...     print(args)  
...     print(b)  
...   
>>> demo_func(1, 2, 100)  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
TypeError: demo_func() missing 1 required keyWord-only argument: 'b'  
>>>   
>>> demo_func(1, 2, b=100)  
(1, 2)  
100  

>>> def demo_func(**kw, a):  
  File "<stdin>", line 1  
    def demo_func(**kw, a):  
                        ^  
SyntaxError: invalid syntax  
>>>   
>>> def demo_func(**kw, a=1):  
  File "<stdin>", line 1  
    def demo_func(**kw, a=1):  
                        ^  
SyntaxError: invalid syntax  
>>>   
>>> def demo_func(**kw, *args):  
  File "<stdin>", line 1  
    def demo_func(**kw, *args):  
                        ^  
SyntaxError: invalid syntax  

def demo_func(arg1, arg2=10, *args, **kw):  
    print("arg1: ", arg1)  
    print("arg2: ", arg2)  
    print("args: ", args)  
    print("kw: ", kw)  

>>> demo_func(1,12, 100, 200, d=1000, e=2000)  
arg1:  1  
arg2:  12  
args:  (100, 200)  
kw:  {'d': 1000, 'e': 2000}  

>>> def demo_func(a, b, *, c):  
...     print(a)  
...     print(b)  
...     print(c)  
...   
>>>   
>>> demo_func(1, 2, 3)  
Traceback (most recent call last):  
  File "<stdin>", line 1, in <module>  
TypeError: demo_func() takes 2 positional arguments but 3 were given  
>>>   
>>> demo_func(1, 2, c=3)  

>>> def add_item(item, source_list):  
...     source_list.append(item)  
...  
>>> alist = [0,1]  
>>> add_item(2, alist)  
>>> alist  
[0, 1, 2]