Modular•2mo ago

How to define nested dict function

(This is a shortened cross post of my stackoverflow question). How do I define a function in Mojo where the argument or return value is a nested structure, like a dictionary. But where the exact structure is not known at compile time because, for example, it is read from disk. For example, how do I type annotate params in the function neural_network to represent a nested dict to keep the model parameters (i.e., a pytree).

network_params = {
  'linear1': {'weights': Tensor(...), 'bias': 1.0},
  ...
}

fn neural_network(params: Dict, x: Tensor) -> Float64:
  x = params['linear1']['weights'] @ x + params['linear1']['bias']
  ...
  return x

x_input = Tensor(...)
y = neural_network(network_params, x_input)

network_params = {
  'linear1': {'weights': Tensor(...), 'bias': 1.0},
  ...
}

fn neural_network(params: Dict, x: Tensor) -> Float64:
  x = params['linear1']['weights'] @ x + params['linear1']['bias']
  ...
  return x

x_input = Tensor(...)
y = neural_network(network_params, x_input)

Thanks so much!

Stack Overflow

How to define a nested dictionary argument of arbitrary depth

How do I define a function in Mojo where the argument is a nested structure, like a dictionary. But where the exact structure is not known at compile time because, for example, it is read from disk...

3 Replies

capt_falamer•2mo ago

Probably not the best way to do what you're looking for but see the 2 examples below. From example you have though, makes me wonder if you want to use a nested dict or just store each type in its own array.

@value
struct Node:
    var dict: Dict[String, Variant[String,Node]]

    fn __setitem__(inout self, key: String, val:Variant[String,Node]):
        self.dict[key] = val

    fn __getitem__(self, key: String) raises -> Variant[String,Node]:
        if key in self.dict:
            return self.dict[key]
        else:
            return Variant[String,Node](str('Does not exist'))

alias str_int = Variant[String,Int,StringLiteral]
@value
struct Node2:
    var dict: Dict[String, Node2]
    var value: str_int

    fn __setitem__(inout self, key: String, n: Node2):
        self.dict[key] = n

    fn __getitem__(self, key: String) raises -> Node2:
        if key in self.dict:
            return self.dict[key]
        else:
            return Node2(Dict[String, Node2](), '')

def main():
    n = Node(Dict[String, Variant[String,Node]]())
    var a1 = Variant[String,Node](str('123'))
    var a2 = Variant[String,Node](str('Pike'))
    var a3 = Variant[String,Node](str('NY'))
    var add = Node(Dict[String, Variant[String,Node]]())
    add['street'] = a1
    add['city'] = a2
    add['state'] = a3
    n['Address'] = add
    print(n['Address'][Node]['street'][String])
    print(n['Address'][Node]['city'][String])
    print(n['Address'][Node]['state'][String])

    n2 = Node2(Dict[String, Node2](), str_int(''))

    n2['user'] = Node2(Dict[String, Node2](), str_int('Allise'))
    print(n2['user'].value[StringLiteral])

    n2['address'] = Node2(Dict[String, Node2](), str_int(''))
    n2['address']['street'] = Node2(Dict[String, Node2](), str_int(123))
    n2['address']['city'] = Node2(Dict[String, Node2](), str_int('Pike'))
    n2['address']['state'] = Node2(Dict[String, Node2](), str_int('NY'))

@value
struct Node:
    var dict: Dict[String, Variant[String,Node]]

    fn __setitem__(inout self, key: String, val:Variant[String,Node]):
        self.dict[key] = val

    fn __getitem__(self, key: String) raises -> Variant[String,Node]:
        if key in self.dict:
            return self.dict[key]
        else:
            return Variant[String,Node](str('Does not exist'))

alias str_int = Variant[String,Int,StringLiteral]
@value
struct Node2:
    var dict: Dict[String, Node2]
    var value: str_int

    fn __setitem__(inout self, key: String, n: Node2):
        self.dict[key] = n

    fn __getitem__(self, key: String) raises -> Node2:
        if key in self.dict:
            return self.dict[key]
        else:
            return Node2(Dict[String, Node2](), '')

def main():
    n = Node(Dict[String, Variant[String,Node]]())
    var a1 = Variant[String,Node](str('123'))
    var a2 = Variant[String,Node](str('Pike'))
    var a3 = Variant[String,Node](str('NY'))
    var add = Node(Dict[String, Variant[String,Node]]())
    add['street'] = a1
    add['city'] = a2
    add['state'] = a3
    n['Address'] = add
    print(n['Address'][Node]['street'][String])
    print(n['Address'][Node]['city'][String])
    print(n['Address'][Node]['state'][String])

    n2 = Node2(Dict[String, Node2](), str_int(''))

    n2['user'] = Node2(Dict[String, Node2](), str_int('Allise'))
    print(n2['user'].value[StringLiteral])

    n2['address'] = Node2(Dict[String, Node2](), str_int(''))
    n2['address']['street'] = Node2(Dict[String, Node2](), str_int(123))
    n2['address']['city'] = Node2(Dict[String, Node2](), str_int('Pike'))
    n2['address']['state'] = Node2(Dict[String, Node2](), str_int('NY'))

capt_falamer•2mo ago

Also if you are looking at parsing (or better more fleshed out code) I recommend checking out https://www.modular.com/modverse/modverse-42 specifically Pholmola's project

Modverse #42: Magic is the best way to build with MAX and Mojo

Welcome to Modverse #42, covering blogs, videos, tutorials, community projects, MAX, and Mojo!

HylkeOP•2mo ago

Thanks for the pointers, that's a big help!

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How to define nested dict function