Detailed Explanation of the Usage of * in python

1, for the multiplication sign

2. Represents multiples, such as:

def T(msg,time=1):
  print((msg+' ')*time)

T ( 'hi',3 ) 

Print results (print 3 times):

hi hi hi

3. Individual *

(1) For example: * parameter is used to accept any number of parameters and put them in a tuple.

>>> def demo(*p):
  print(p)

  
>>> demo(1,2,3)
(1, 2, 3)

(2) When the function calls multiple parameters, it takes lists, tuples, collections, dictionaries and other iterable objects as arguments, and adds * in front of them

For example, * (1, 2, 3) interpreter will automatically unpack and then pass it to multiple univariate parameters (the number of parameters should correspond to the same).

>>> def d(a,b,c):
  print(a,b,c)

  
>>> d(1,2,3)
1 2 3


>>> a=[1,2,3]
>>> b=[1,2,3]
>>> c=[1,2,3]
>>> d(a,b,c)
[1, 2, 3] [1, 2, 3] [1, 2, 3]

  
>>> d(*a)
1 2 3

Tip: Sequence unpacking should be processed before key parameters and ** parameters

4. Two * * such as: **parameter is used to receive multiple arguments in the form of assignments similar to key parameter 1 and put them into a dictionary (that is, convert the parameters of this function into a dictionary).

>>> def demo(**p):
  for i in p.items():
    print(i)

    
>>> demo(x=1,y=2)
('x', 1)
('y', 2)