对python中的装包与解包实例详解

def fun(n, *args):
  print(n)
  print(args)   # 未拆包
  print(*args)  # 进行拆包
fun(1,2,3,4)

1
(2, 3, 4)
2 3 4

def fun(**kwargs):
  print(kwargs)    # 未拆包
  print(*kwargs) # 进行拆包
fun(a=1, b=2)

{'a': 1, 'b': 2}
a b

def fun(*args, **kwargs):
  for arg in args:
    print(arg)
  for k, v in kwargs.items():
    print(k, v)
  print('-'*50)
fun(a, c)  # 参数都赋值给args，并没有kwargs的参数
fun(*a, *c)   # 解压的参数都赋值给args 等价为 1, 2, 3, 'a', 'b', 'c'
fun(*a, **c)  # a解压给args，c解压给kwargs 等价为 1, 2, 3, 'a'=1, 'b'=2, 'c'=3

[1, 2, 3]
{'a': 1, 'b': 2, 'c': 3}
--------------------------------------------------
1
2
3
a
b
c
--------------------------------------------------
1
2
3
a 1
b 2
c 3

def myfun(a, *b):
  print(a)
  print(b)
myfun(a=1,2,3,4)


  myfun(a=1,2,3,4)
       ^
SyntaxError: positional argument follows keyword argument

def myfun(a, *b, c=None):
  print(a)
  print(b)
  print(c)
myfun(1,2,3,c=4)

1
(2, 3)
4

def myfun(*, a, b):
  print(a)
  print(b)
myfun(a=1, b=2)

def myfun(a, *b, c, **d):
  print(a)
  print(b)
  print(c)
  print(d)
myfun(1, 2, w=6, c=3, d=4, e=5)   # 记住可变参数(*)之前不能指定参数名

1
(2,)
3
{'w': 6, 'd': 4, 'e': 5}