dict to boolean expression, how to?

[Steven D'Aprano]

On Fri, 01 Aug 2014 14:26:38 +0000, Alex van der Spek wrote:

[...]
> bool = ((df['a'] == 1) & (df['A'] == 0) |
>          (df['b'] == 1) & (df['B'] == 0) |
>          (df['c'] == 1) & (df['C'] == 0))
> 
> I do know eval() lends itself to code injection but can't say I am fully
> aware of its dangers. It seemed like a handy tool to me.

And in expert hands, it can be. But I can't see how you're using eval in 
this case. Since you're not having any success, perhaps it's not as handy 
as you imagine?

Did you try the suggestion to use any( ... )? Did it work?

 
> This newsgroup scares me, it appears to be for professional computer
> scientists only, 

Not even close! Some of us aren't even professional programmers!


> the theoretical part is sometimes too much for this
> practical physicist with an old background in FORTRAN.

Oh, I sympathise. I know it can be hard to avoid feeling overwhelmed when 
you are dropped far outside of your comfort zone in a topic you know 
nothing about. But you're a physicist, and therefore you've already 
proven you have the logical skills to reason about quite complex and 
mathematical topics. If you're lost now, I wager it's because you're 
unfamiliar with the territory, not because it's beyond you.

So please, don't be shy about asking people to explain in simpler terms. 
Sometimes we forget that things which are second nature to us are not 
familiar to somebody new to the language. Or we don't want to patronise 
them by assuming that every person asking a question needs their hand-
held and every little detail spelled out in painfully small steps. It's 
quite hard to find the right balance, especially when we don't know your 
level of knowledge.

So please, ask concrete questions, the more specific the better. Don't be 
afraid to ask what unfamiliar terms means.


> Is there a better place to ask questions of this nature?

I don't know of anyone here who is an expert in pandas, so if you ask 
questions which are specific to pandas, we may run into the limits of our 
knowledge. If you can find a dedicated pandas mailing list or other 
forum, they may help too, but I don't know if they will be more or less 
willing to explain the basics about Python.



-- 
Steven