#kwargs

Understand python arguments *args and **kwargs

Most new Python programmers have a hard time figuring out the *args and **kwargs magic variables. So what are they?

*args and **kwargs

Firstly, it is not necessary to write *args or **kwargs. Only the * (asterisk) is necessary. You can use *var and **vars instead. Writing *args and **kwargs is just a convention. So now let’s take a look at *args first.

Usage of *args

*args and…

Function Parameters in Python

By Omer Rosenbaum, Cyber Security Lead @ Israel Tech Challenge

Python is a really cool language. Using Python, we can create readable and powerful scripts really fast, for almost anything. At our Tech Challenge Fellows program, we teach Python as a tool for many different subjects: computer networks, data science, security research and more. We emphasize the use of Python as a tool for a broad variety of subjects.

In this short post, we’ll look into some function definitions in Python, focusing on less common ones.

Default values:

If we want, we can define a function with an argument that has a default value.

>>> def return_number(number=5):

             return number

Now, if we call the function without explicitly assigning a value to "number", it will be assigned it's default value, 5:

>>> return_number()

5

Yet, we can still call it with an explicitly assigned value:

>>> return_number(3)

3

*args

In case we have an unknown amount of arguments, we can use *args. Note that the name *args is a convention, and one can use other names as well, for instance:

>>> def multiply_many(*numbers):

             result = 1

             for number in numbers:

                         result *= number

            return result

>>> multiply_many(5,6,7)

210

>>> multiply_many()

1

>>>

When we pass *args, it's essentially a tuple object. Since Python is so cool, we can easily test this assumption:

>>> def multiply_many(*numbers):

             print type(numbers)

>>> multiply_many()

<type 'tuple'>

**kwargs

Using *args, our functions can receive a variant number of arguments.

Now we can try to provide arguments with names. This time, we'll get a dictionary. Let's see the following example:

>>> def print_ages(**people):

             for (name, age) in people.items():

                       print "%s is %d years old." % (name, age)

>>> print_ages(Yaniv=38, Omer=26)

Omer is 26 years old.

Yaniv is 38 years old.

We can also provide a dictionary to this function:

>>> staff = {"Omerr": 26, "Yaniv": 38}

>>> print_ages(**staff)

             Omerr is 26 years old.

              Yaniv is 38 years old.

Now let's mix things up a bit. Try to test yourself – what will be the output of the function show_everything each time we run it?

>>> def show_everything(number_one, number_two, *args, **kwargs):

             print (number_one, number_two, args, kwargs)

>>> show_everything()

Traceback (most recent call last):

File "<pyshell#212>", line 1, in <module>

      show_everything()

TypeError: show_everything() takes at least 2 arguments (0 given)

>>> show_everything(1,2)

(1, 2, (), {})

>>> show_everything(1,2,3)

(1, 2, (3,), {})

>>> show_everything(1,2,3,4,5)

(1, 2, (3, 4, 5), {})

>>> show_everything(1,2,3,4,5, omer=1)

(1, 2, (3, 4, 5), {'omer': 1})

>>> show_everything(1,2,3,4,5, omer=1, yaniv=2)

(1, 2, (3, 4, 5), {'omer': 1, 'yaniv': 2})

We have seen a few different function definitions, using default values, *args and **kwargs. We've also seen how fun it can be to just test things using Python:)

Omer, a Networks and Cyber expert is the Cyber-Security Lead at Israel Tech Challenge. Omer served seven years in technological and team leading jobs in the IDF. He has created a lot of content for the Cyber curriculum of "Gvahim" program, teaching Cyber in Israeli Highschools, and is the author of the textbook "Computer Networks". 

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Fixed Proper way to use **kwargs in Python #dev #it #asnwer

Proper way to use **kwargs in Python

What is the proper way to use **kwargs in Python when it comes to default values?

kwargs returns a dictionary, but what is the best way to set default values, or is there one? Should I just access it as a dictionary? Use get function?

class ExampleClass: def __init__(self, **kwargs): self.val = kwargs['val'] self.val2 = kwargs.get('val2')

A simple question,…

Fixed Understanding kwargs in Python #dev #it #asnwer

Understanding kwargs in Python

What are the uses for **kwargs in Python?

I know you can do an objects.filter on a table and pass in a **kwargs argument.

Can I also do this for specifying time deltas i.e. timedelta(hours = time1)?

How exactly does it work? Is it classes as ‘unpacking’? Like a,b=1,2?

Answer: Understanding kwargs in Python

kwargs is just a dictionary that is added to the parameters.