Newby - what is "(**dict(form.vars))"

[Chops]

I am just learning Web2py

I have an understanding of dict but now I find it used with two asterisks before it and I can't seem to find an explanation!!

Can it be used with anything other than a form? ((**dict(form.vars))?

Can I use the two asterisks on other bits of code to server a common purpose?

Thanks in advance

[shapova...@gmail.com]

hi! 

Don't worry it's pretty common question for newcomers :)

This is called Function Argument Packaging and Function Argument Unpackaging.

arguments could be packaged into list or dictionary:

* - position based arguments

** - name based arguments

>>> def f(*a, **b):

return a, b

>>> x, y = f(3, 'hello', c=4, test='world')

>>> print x

(3, 'hello')

>>> print y

{'c':4, 'test':'world'}

and vice versa, arguments could be extracted for functions

>>> def f(a, b):

return a + b

>>> c = (1, 2)

>>> print f(*c)

3

>>> def f(a, b):

return a + b

>>> c = {'a':1, 'b':2}

>>> print f(**c)

3

[Bruce Lamb]

Wow!! this is a bit mind bending - it will take some processing time!!

Really appreciate your VERY useful and quick response.

--
Resources:
- http://web2py.com
- http://web2py.com/book (Documentation)
- http://github.com/web2py/web2py (Source code)
- https://code.google.com/p/web2py/issues/list (Report Issues)
---
You received this message because you are subscribed to a topic in the Google Groups "web2py-users" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/web2py/VyouPnp0rPU/unsubscribe.
To unsubscribe from this group and all its topics, send an email to web2py+un...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.