(1) I am trying to replace items values, without a loop only with a python in function, of an array.
(2) I am trying to get, without a loop only with a predicate, all items containing a certain value.
What do I need to change to do (1) and (2) (probably everything) 
question9.gh (5.0 KB)
Can you explain better what you want to do?
Only one value in your lists is equal to 1 or 2 (there is a single “2”).
How should the replacing work?
Also, you are in c# context, not python.
In c# there is this:
List[int] ints;
foreach(int i in ints){
Print(i.ToString())
}An array of 100 times 0.
An list x of certain item numbers
An list y of certain item numbers.
(1)
I want to replace all array items with 1 if the item is in list x, with something similar like ‘in’ as with python.
I want to replace all array items with 2 if the item is in list y, with something similar like ‘in’ as with python.
(2)
I want to make a new array containing all item numbers of the array when the value is 2.
Did I explain it better 
… what? 
Sorta.
Try this:
using System.Linq;
private void RunScript(List<int> x, List<int> y, ref object A)
{
List<int> ints = Enumerable.Repeat(0, 100).ToList();
List<int> ints_copy = new List<int>(ints);
for(int i = 0;i < ints.Count();i++){
if(x.Contains(ints[i])) ints_copy[i] = 1;
else if(y.Contains(ints[i])) ints_copy[i] = 2;
}
A = ints_copy;
}
question9.gh (6.1 KB)
Do you also know about an Array.IndexOfFindAll
by which I mean,
So I now have an array with 1’s and 2’s in it but mostly 0’s, I now want all indices of the array which hold an 2.
When doing Array.IndexOf it only gives me the first index number with 2. But I want all indices with 2.
I am trying to find a way doing that without a loop. Is that possible?
Or doing it with an predicate x=> x==2 give index number; ToArray() or ToList().
I think this? “in” in Python is Contains() in C#. there is no as cool as “in” equivalent.
List < int> X = new List<int>(){4,7};
List < int> Y = new List<int>(){2,3};
var vals = from val in Enumerable.Range(0, 10) select X.Contains(val) ? 1 : Y.Contains(val) ? 2 : val;
A = vals;
condition ?A:B returna A if the condition is true and B if the condition is not true.
It can be nested deep such like
condition1?A:condition2?B:C
A C# big secret is that Where() takes an index as the second parameter.
I wish (val,I) in vals where val==1 select i; also works but it does not.
List <int> vals = new List<int>{0,2,1,2,1,0,0,2,1};
var X2 = vals.Where((Val, i) => (Val == 1)).Select((Val, i) => i);
var Y2 = vals.Where((Val, i) => (Val == 2)).Select((Val, i) => i);This one works for me also with arrays, thank you 
Hmm… I thought this should work too but I am doing something wrong
Do you might know what I am doing wrong
question9a.gh (4.5 KB)
To make it more complex, to learn different ways of doing things, what am I doing wrong here
// Making an array existing out of 0's
int[] arr = Enumerable.Repeat(0, 100).ToArray();
// Changing the array.
int[] itms1 = new int[]{0,1,2,12,14,20};
int[] itms2 = new int[]{42,43,55,80,91};
foreach (int i in itms1){
arr[i] = 1;
}
foreach (int i in itms2){
arr[i] = 2;
}
// Making a list of itms based on conditions.
int[] itms3 = new int[]{0,1,12,42};
List<int> non0itms = new List<int>();
foreach(Enumerable.Range(0,arr.Length)){
if (arr[i] == 1 or arr[i] == 2 and itms3.Contains[i]){
non0itms.Add(i);
}
}
question9b.gh (8.2 KB)
I think variable names should not start with a number…
I see
About the array it says that the System.Array does not have a ‘Where’ method.
To do something similar, continue using predicates, do you might know how I can do that
Done
I have had this in a previous attempts, and it gives me 0 and 1 while it must be 8 and 11 so, do you might know how I have to write the predicate differently
question9c.gh (4.1 KB)
Oops, it was my mistake.
The first Where gives a list with two items, so the second Select loops over only two items.
Maybe Zip?
int[] arr = new int[8]{0,1,0,1,0,1,0,1};
A=arr.Zip(Enumerable.Range(0,arr.Length),(val,i)=>(new Tuple<int,int>(val,i))).Where((val)=>(val.Item1==1)).Select((val)=>(val.Item2));Now that I can rewrite it to my favorite syntax.
int[] arr = new int[8]{0,1,0,1,0,1,0,1};
A=from val in arr.Zip(Enumerable.Range(0,arr.Length),(val,i)=>(new Tuple<int,int>(val,i))) where val.Item1==1 select val.Item2;About your favorite syntax I am just curious in different comparable code. What do I have to change it to let it work
question9d.gh (9.1 KB)
The forum doesn’t show square brackets correctly when it’s not wrapped in a code environment.
arr is an array. so the type is not int but
int[]
Hope this works this time.
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