[Python] Non-Keyword Arguments and Keyword Arguments

Python has methods to pass a number of arguments to a function.

Let's figure it out.

Non-Keyword Arguments

It is not compulsory, but it is mainly used in the form *args.

 

This is the basic usage.

def testArgs(*args):
    for arg in args:
    	print(arg)

testArgs('hello', 'world', 7, 3.14)
# hello
# world
# 7
# 3.14

You can pass a number of arguments with this method.

 

Let's test with the normal arguments.

def testArgs(arg1, arg2, *args):
    for arg in args:
    	print(arg)
    print('=======')
    print(f'{arg1}, {arg2}')

testArgs('hello', 'world', 7, 3.14)
# 7
# 3.14
# =======
# hello, world

After the passed arguments are assigned in order, all remaining arguments are assigned to non-keyword arguments.

You have to put the non-keyword arguments to the last.

 

You can put the non-keyword arguments to the first location, but you need to pass arguments with the name of arguments.

def testArgs(*args, arg1, arg2):
    for arg in args:
        print(arg)
    print('=======')
    print(f'{arg1}, {arg2}')

testArgs('hello', 'world', arg1=7, arg2=3.14)
# hello
# world
# =======
# 7, 3.14

You can't put the non-keyword arguments to the other locations.

Keyword Arguments

Keyword arguments is similar to non-keyword arguments except that it can have key, value pair.

def testKwargs(**kwargs):  
    for key, value in kwargs.items(): 
        print (f'{key}, {value}')

testKwargs(key1='hello', key2=7, key3=3.14)
# key1, hello
# key2, 7
# key3, 3.14

 

Now, let's test with the normal arguments.

def testKwargs(arg1, arg2, **kwargs):
    print(f'{arg1}{arg2}')
    for key, value in kwargs.items(): 
        print (f'{key}, {value}')

testKwargs('python', 3, key1='hello', key2=7, key3=3.14)
# python3
# key1, hello
# key2, 7
# key3, 3.14

testKwargs(arg2='python', arg1=3, key1='hello', key2=7, key3=3.14)
# 3python
# key1, hello
# key2, 7
# key3, 3.14

It is the same as non-keyword arguments.

Both Non-Keyword Arguments and Keyword Arguments

We can even use both non-keyword arguments and keyword arguments simultaneously.

def testFunc(*args, **kwargs): 
    print(f'args: {args}') 
    print(f'kwargs: {kwargs}') 
  
testFunc('hello', 'world', 3, one=1, two='second',three=3.14)
# args: ('hello', 'world', 3)
# kwargs: {'one': 1, 'two': 'second', 'three': 3.14}

It is distinguished by the name of arguments.

And it can use with normal arguments.

 

Let's go over one last thing.

argsTuple = (1, 2, 3)
argsList = ['one', 'two', 'three']
kwargs = {'arg1': 1, 'arg2': 2, 'arg3': 3}

def testArgs(arg1, arg2, arg3): 
    print(f'arg1: {arg1}, arg2: {arg2}, arg3: {arg3}')

def testKwargs(arg1, arg2, arg3): 
    print(f'arg1: {arg1}, arg2: {arg2}, arg3: {arg3}')
  
testArgs(*argsTuple) 
# arg1: 1, arg2: 2, arg3: 3

testArgs(*argsList) 
# arg1: one, arg2: two, arg3: three

testKwargs(**kwargs) 
# arg1: 1, arg2: 2, arg3: 3

When using this, the same argument name as the key in the dictionary must be used.

 

You can leave now, please use this in your code.