vsoler wrote:
Hi,
Not sure this is the best group to post, but I cannot think of any
other.
My application would contain a limited set of "cells" represented by
the instances of a Cell class:
class Cell:
...
A1=Cell(7)
A2=Cell(2*A1)
A3=Cell(3*A1+A2)
A4=Cell(A3*4)
Of course, A1 = 7, A2 = 14, A3 = 35 and A4 = 140
Now, I somehow want to be able to show a dependency tree
1 level dependency trees
A1: None
A2: A1
A3: A1, A2
A4: A3
All levels dependency trees
A1: None
A2: A1
A3: A1, A2
A4: A3, A2, A1
Leaf + values dependency trees:
A1: 7
A2: A1=7, 2
A3: 3, A1=7, 2
A4: 3, A1=7, 2, 4
What I'd like to know is:
1) what are, in your opinion, the basic elements of the Cell class?
2) Do I need a parser to evaluate the formulas like “3*A1+A2”? Can you
recommend one library that already contains one?
3) Do I need a tree data structure to represent my data? would the
tree be an attribute of the class instance?
I imagine a lot can be said on these questions. What I am looking for
is some hints that help me get out of where I am now.
Any help is highly appreciated.
As well as considering the other replies, you don't necessarily need to
parse the expressions yourself.
If A1 is a cell then 2*A1 tries to call the __rmul__ method of A1 (and
A1*2 tries to call the __mul__ method of A1), so you could have it
return a formula object that will multiply and return the numeric value
of self (A1) by 2 when its own numeric value is requested. This means
that a cell could be initialised with either a number or a formula.
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