[info] what dose it mean when asterisk (*) appear in python function signature?

In Python, an asterisk (*) in a function signature can have several meanings depending on its context. Here are the main uses:

1. Variable Positional Arguments (*args): When a single asterisk precedes a parameter, it collects all additional positional arguments passed to the function into a tuple.

   
   def my_function(*args):
       print(args)
   
   my_function(1, 2, 3)  # Output: (1, 2, 3)
   

2. Keyword-Only Arguments: When an asterisk is placed in the function signature without a variable name, it indicates that all subsequent parameters must be specified as keyword arguments.

   
   def my_function(a, b, *, c):
       print(a, b, c)
   
   my_function(1, 2, c=3)  # Valid
   my_function(1, 2, 3)    # Invalid: TypeError
   

3. Variable Keyword Arguments (**kwargs): When a double asterisk precedes a parameter, it collects all additional keyword arguments passed to the function into a dictionary.

   
   def my_function(**kwargs):
       print(kwargs)
   
   my_function(a=1, b=2)  # Output: {'a': 1, 'b': 2}
   

4. Unpacking Arguments: An asterisk can also be used in the function call to unpack a list or tuple into positional arguments, or a dictionary into keyword arguments.

   def my_function(a, b, c):
       print(a, b, c)
   
   args = (1, 2, 3)
   my_function(*args)  # Output: 1 2 3
   
   kwargs = {'a': 1, 'b': 2, 'c': 3}
   my_function(**kwargs)  # Output: 1 2 3
   

Each of these uses helps make functions more flexible and allows for more dynamic handling of arguments.