Error with method append with string

[warm wing]

When im try use List for string a get error

    let list = List[String]()
    list.append("123")```

Error:
```/home/asifar/http/main.🔥:38:16: error: no matching function in call to 'append': 
    list.append("123")
    ~~~~~~~~~~~^~~~~~~
list.mojo:133:5: note: candidate not viable: method argument #0 cannot bind generic !mlirtype to memory-only type 'String'
    fn append(inout self, value: T):
    ^
list.mojo:139:5: note: candidate not viable: method argument #0 cannot be converted from 'StringLiteral' to 'List[String]'
    fn append(inout self, list: List[T]):
    ^
/home/asifar/.modular/pkg/packages.modular.com_mojo/bin/mojo: error: failed to parse the provided Mojo```

[warped fog]

Hey, the error message is a bit unclear, but it means that you can only use simple @register_passable structs in lists (which String is not)
You can use a StringLiteral which is immutable but may be enough for what you're trying to achieve.

[warm wing]

    list.append("123")
               ^
/home/asifar/http/main.:fire::37:5: note: 'list' declared here
    let list = List[StringLiteral]()
    ^
/home/asifar/.modular/pkg/packages.modular.com_mojo/bin/mojo: error: failed to run the pass manager```
I made StringLiteral, and already another error.

[warped fog]

append is a mutating method that must modify the underlying storage, but you declared the variable as let (immutable)
You have to declare the list as a var

[warm wing]

Thanks It works)

[warped fog]

If you still want a list that you can't modify later you can initialize it upfront

let list: List[StringLiteral] = ["a", "b", "c"]

[warm wing]

Is there a way to create a list for a String type on the heap?

[warped fog]

As far as I know you can't have pointers in a list yet either so I doubt it
Not sure why considering it has no destructor but Pointer is not @register_passable

[daring nacelle]

how to get rid of this warning

[warped fog]

I don’t think this is related so this should be a different question

You’re not using the potential return values, discard them by assigning these to an underscore with _ =

[daring nacelle]

_= is it the only way
here the return values are just useless

[warped fog]

You’re interacting with Python, an untyped, dynamic language, so there’s no way to be sure it won’t actually return anything

This is not a problem unique to Mojo when it comes to this kind of interoperability