Python中参数打包和解包的实现

# A sample function that takes 4 arguments
# and prints them.
def fun(a, b, c, d):
    print(a, b, c, d)
# Driver Code
my_list = [1, 2, 3, 4]
# This doesn't work
fun(my_list)

# A sample function that takes 4 arguments
# and prints the,
def fun(a, b, c, d):
    print(a, b, c, d)
# Driver Code
my_list = [1, 2, 3, 4]
# Unpacking list into four arguments
fun(*my_list)

# Error when len(args) != no of actual arguments
# required by the function
args = [0, 1, 4, 9]
def func(a, b, c):
    return a + b + c
# calling function with unpacking args
func(*args)

>>>
>>> range(3, 6)  # normal call with separate arguments
[3, 4, 5]
>>> args = [3, 6]
>>> range(*args)  # call with arguments unpacked from a list
[3, 4, 5]

# A Python program to demonstrate use
# of packing
# This function uses packing to sum
# unknown number of arguments
def mySum(*args):
    return sum(args)
# Driver code
print(mySum(1, 2, 3, 4, 5))
print(mySum(10, 20))

# A Python program to demonstrate both packing and
# unpacking.
# A sample python function that takes three arguments
# and prints them
def fun1(a, b, c):
    print(a, b, c)
# Another sample function.
# This is an example of PACKING. All arguments passed
# to fun2 are packed into tuple *args.
def fun2(*args):
    # Convert args tuple to a list so we can modify it
    args = list(args)
    # Modifying args
    args[0] = 'python'
    args[1] = 'awesome'
    # UNPACKING args and calling fun1()
    fun1(*args)
# Driver code
fun2('Hello', 'beautiful', 'world!')

# A sample program to demonstrate unpacking of
# dictionary items using **
def fun(a, b, c):
    print(a, b, c)
# A call with unpacking of dictionary
d = {'a':2, 'b':4, 'c':10}
fun(**d)

# A Python program to demonstrate packing of
# dictionary items using **
def fun(**kwargs):
    # kwargs is a dict
    print(type(kwargs))
    # Printing dictionary items
    for key in kwargs:
        print("%s = %s" % (key, kwargs[key]))
# Driver code
fun(name="geeks", ID="101", language="Python")