十一个案例带你吃透Python函数参数

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]