how to use & and | in attrs

Question

i need to make a attrs to a button when ((a = true and state = done) or (a= false and state = available)
what should i put in the button to make it works?
i tried
<button name = "button_a" string ="Button A" attrs="{'invisible':[('&',('a','=',True),('state','=','done')),('&',('a','=',False),('state','=','available'))]}"/>
and it says there is error

Temur · Accepted Answer

actually you've two errors:
1. you can't use special character & in XML directly, you should write it with it's xml code ( we discussed it here [1] )
2. conditional statement is not a valid prefix notation statement, you should write the statement in the *prefix notation* ( we discussed it here [2] )
correct the two errors and you're done:
<button name = "button_a" string ="Button A" attrs="{'invisible':['|','&',('a','=',True),('state','=','done'),'&',('a','=',False),('state','=','availa

Zbik · Answer

Use the Polish notation [1]
About your question:
(A and B) or (C and D)
should converted to the polish notation as
or and A B and C D
in your example:
['|','&',('a','=',True),('state','=','done'),'&',('a','=',False),('state','=','available')]
in xml (see @Temur post)
['|','&',('a','=',True),('state','=','done'),'&',('a','=',False),('state','=','available')]

[1] https://en.wikipedia.org/wiki/Polish_notation

Anil Kesariya · Answer

Hi
Here you go!
By default & Operator applied so no need to use & operator
<button name = "button_a" string ="Button A" attrs="{'invisible':['|', '&',('a','=',True),('state','=','done'),'&',('a','=',False),('state','=','available')]}"/>
Hope, This will help you
Rgds,
Anil.

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