Discuss the most possible ways of passing parameters in the python functions.

Parameter passing in a function

In addition to positional parameters, there are few other parameter types including variadic parameters:

def p2f(name, *content, namedpara=None, **attrs):
    print(f'name:{name}')
    print(f'content:{content}')
    print(f'namedpara:{namedpara}')
    print(f'attrs:{attrs}')

above positional parameter is the first one, named parameter is namedpara.

p2f('ojitha')

output

name:ojitha
content:()
namedpara:None
attrs:{}

if your pass extra, it is for content tuple as follows

p2f('ojitha','hewa', 'kum')

output

name:ojitha
content:('hewa', 'kum')
namedpara:None
attrs:{}

and

p2f('ojitha',id=1)

output

name:ojitha
content:()
named parameters:None
attrs:{'id': 1}

if you pass parameters as follows

params = {'name':'ojitha', 'last_name':'kuma'}
p2f(**params)

the output is

name:oj
content:()
namedpara:None
attrs:{'last_name': 'kuma'}

With type hints

from typing import Optional


def p2f(name: str
    , *content: str
    , namedpara: Optional[str] = None
    , **attrs: str):
    
    print(f'name:{name}')
    print(f'content:{content}')
    print(f'namedpara:{namedpara}')
    print(f'attrs:{attrs}')

if you have different value to pass in the variadic parameters:

from typing import Optional, Union

def p2f(name: str
    , *content: Union[str,int]
    , namedpara: Optional[str] = None
    , **attrs: Union[str,int]) :
    
    ...

Keyword-only arguments

This will never capture unnamed positional arguments, for example

def f(p1,*,p2):
    print(p1,p2)

and if you call the function

f(1,2)

The ouput is an error

TypeError                                 Traceback (most recent call last)
Cell In[11], line 1
----> 1 f(1,2)

TypeError: f() takes 1 positional argument but 2 were given

Therefore you have to call the above function as follows

f(1, p2 =2)

Positional only

For example

# since python 3.8
# position only parameters

def f(p1, p2, /, p3):
    print(p1, p2, p3)

if you call the function

f(1, p2=2, p3=3)

the output is

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[25], line 1
----> 1 f(1, p2=2, p3=3)

TypeError: f() got some positional-only arguments passed as keyword arguments: 'p2'

but, if you call as follows:

f(1,2, p3=3)
# output is 1 2 3

Type Hints

You can use the following type Hints to define the method signature:

from typing import Optional, Union


def p2f(name: str
    , *content: Union[str,int]
    , namedpara: Optional[str] = None
    , **attrs: Union[str,int]) :

    print(f'name:{name}')
    print(f'content:{content}')
    print(f'namedpara:{namedpara}')
    print(f'attrs:{attrs}')

If you call the above function p2f('ojitha','hewa',21,id1='test', id2=2), the output is:

name:ojitha
content:('hewa', 21)
namedpara:None
attrs:{'id1': 'test', 'id2': 2}