CODEWITHSUNDEEP
pythonfunctionoptional-parameters
user615536
user615536

Reputation: 559

Optional arguments without a default value

The Python Documentation for parameters says the following:

Parameter - A named entity in a function (or method) definition that specifies an argument (or in some cases, arguments) that the function can accept... Parameters can specify both optional and required arguments, as well as default values for some optional arguments.

Purely out of curiosity, I am wondering why the word some was included. Is it possible to have an optional argument without a default value?

Upvotes: 8

Views: 13964

Answers (3)

wjandrea
wjandrea

Reputation: 32921

*args and **kwargs are optional arguments without default values

-- comment by Pranav Hosangadi

Upvotes: 1

DevLounge
DevLounge

Reputation: 8437

In recent versions you can define functions arguments multiple ways. Here is how they can be defined and called:

def fun(a, b, c='foo'):
    ...
fun(1, 2)
fun(1, 2, 'bar')
fun(1, b=2)
fun(1, b=2, c='bar')
fun(a=1, b=2, c='bar')

where a and b are positional or keyword args and c is an optional positional or keyword arg

or

def fun(a, b, *, c, d='foo'):
    ...
fun(1, 2, c='bar')
fun(1, b=2, c='bar', d='baz')
fun(a=1, b=2, c='bar', d='baz')

where a and b are positional or keyword args and c is a mandatory kwarg and d is an optional kwarg

or

def fun(a, b, /, c, *, d, e='foo'):
    ...
fun(1, 2, 3)
fun(1, 2, c=3)
fun(1, 2, c=3, d='bar')

where a and b are positional only args, c is a positional or keyword arg and d is a mandatory kwarg and e is an optional kwarg

Upvotes: 5

Hook
Hook

Reputation: 354

The * prefix means "arbitrary number of positional parameters", and parameters prefixed by it can be declared without default value. The word 'some' relates to that reason, you don't have to provide default values for all optional arguments.

Upvotes: 2

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