(Sep-09-2017, 11:03 PM)Larz60+ Wrote: It looks like the name of the function is automatically passed as argument b:

def test1(a, b='test'):
    print(a)
    print(b
     
test1('hello', 'world')

Output:
hello
world

def test1(a,*, b='test'):
    print(a)
    print(b)
     
test1('hello', 'world')

Output:
Traceback (most recent call last):
File "e:\1py_div\div_code\pos.py", line 32, in <module>
test1('hello', 'world')
TypeError: test1() takes 1 positional argument but 2 were given

def test1(a,*, b='test'):
    print(a)
    print(b)
     
test1('hello', b='world')

Output:
hello
world

(Sep-10-2017, 12:23 AM)Skaperen Wrote: so how can a definition of an argument specifying that it can be given either way define the difference between a required argument and one that is not required (e.g. calling f() above with just one positional  argument)?

λ ptpython
>>> def f(positional, either_way_with_default_value='foo',*, only_as_a_named_option='bar'):
...     return positional,either_way_with_default_value,only_as_a_named_option

>>> f(1)
(1, 'foo', 'bar')

>>> f(1, 2)
(1, 2, 'bar')

>>> f(1, 2, 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: f() takes from 1 to 2 positional arguments but 3 were given
f() takes from 1 to 2 positional arguments but 3 were given

>>> f(1, 2, only_as_a_named_option=3)
(1, 2, 3)

>>> def f(positional, either_way_with_default_value='foo', only_as_a_named_option='bar'):
...     return positional,either_way_with_default_value,only_as_a_named_option

>>> f(1)
(1, 'foo', 'bar')

>>> f(1, 2)
(1, 2, 'bar')

>>> f(1, 2, 3)
(1, 2, 3)

(Sep-10-2017, 01:50 AM)Larz60+ Wrote: I am confusing myself. Of course the default value of b is 'test'. But now I'm not sure what the purpose of * is.

(Sep-09-2017, 11:03 PM)Larz60+ Wrote: It looks like the name of the function is automatically passed as argument b: