Skip to main content
Max PlatformDocsCompanyBlogModCon
Max PlatformDocsCompanyBlogModCon
Contact salesSign in

struct

Dict

A container that stores key-value pairs.

The key type and value type must be specified statically, unlike a Python dictionary, which can accept arbitrary key and value types.

The key type must implement the KeyElement trait, which encompasses Movable, Hashable, and EqualityComparable. It also includes CollectionElement and Copyable until we have references.

The value type must implement the CollectionElement trait.

Usage:

from collections import Dict
var d = Dict[String, Int]()
d["a"] = 1
d["b"] = 2
print(len(d))      # prints 2
print(d["a"])      # prints 1
print(d.pop("b"))  # prints 2
print(len(d))      # prints 1

Parameters​

  • ​K (KeyElement): The type of the dictionary key. Must be Hashable and EqualityComparable so we can find the key in the map.
  • ​V (CollectionElement): The value type of the dictionary. Currently must be CollectionElement.

Aliases​

  • EMPTY = -1:
  • REMOVED = -2:

Fields​

  • ​size (Int): The number of elements currently stored in the dict.

Implemented traits​

AnyType, Boolable, CollectionElement, Copyable, Movable, Sized

Methods​

__init__​

__init__(inout self: Self, /)

Initialize an empty dictiontary.

__init__(inout self: Self, /, existing: Self)

Copy an existing dictiontary.

Args:

  • ​existing (Self): The existing dict.

__copyinit__​

__copyinit__(inout self: Self, /, existing: Self)

Copy an existing dictiontary.

Args:

  • ​existing (Self): The existing dict.

__moveinit__​

__moveinit__(inout self: Self, /, owned existing: Self)

Move data of an existing dict into a new one.

Args:

  • ​existing (Self): The existing dict.

__bool__​

__bool__(self: Self) -> Bool

Check if the dictionary is empty or not.

Returns:

False if the dictionary is empty, True if there is at least one element.

__getitem__​

__getitem__(self: Self, key: K) -> V

Retrieve a value out of the dictionary.

Args:

  • ​key (K): The key to retrieve.

Returns:

The value associated with the key, if it's present.

Raises:

"KeyError" if the key isn't present.

__setitem__​

__setitem__(inout self: Self, key: K, value: V)

Set a value in the dictionary by key.

Args:

  • ​key (K): The key to associate with the specified value.
  • ​value (V): The data to store in the dictionary.

__contains__​

__contains__(self: Self, key: K) -> Bool

Check if a given key is in the dictionary or not.

Args:

  • ​key (K): The key to check.

Returns:

True if there key exists in the dictionary, False otherwise.

__len__​

__len__(self: Self) -> Int

The number of elements currenly stored in the dictionary.

__str__​

static __str__[T: StringableKeyElement, U: StringableCollectionElement](self: Dict[T, U]) -> String

Returns a string representation of a Dict.

Note that since we can't condition methods on a trait yet, the way to call this method is a bit special. Here is an example below:

var my_dict = Dict[Int, Float64]()
my_dict[1] = 1.1
my_dict[2] = 2.2
dict_as_string = __type_of(my_dict).__str__(my_dict)
print(dict_as_string)
# prints "{1: 1.1, 2: 2.2}"

When the compiler supports conditional methods, then a simple str(my_dict) will be enough.

Parameters:

  • ​T (StringableKeyElement): The type of the keys in the Dict. Must implement the traits Stringable and KeyElement.
  • ​U (StringableCollectionElement): The type of the values in the Dict. Must implement the traits Stringable and CollectionElement.

Args:

  • ​self (Dict[T, U]): The Dict to represent as a string.

Returns:

A string representation of the Dict.

find​

find(self: Self, key: K) -> Optional[V]

Find a value in the dictionary by key.

Args:

  • ​key (K): The key to search for in the dictionary.

Returns:

An optional value containing a copy of the value if it was present, otherwise an empty Optional.

pop​

pop(inout self: Self, key: K, owned default: Optional[V] = #kgen.none) -> V

Remove a value from the dictionary by key.

Args:

  • ​key (K): The key to remove from the dictionary.
  • ​default (Optional[V]): Optionally provide a default value to return if the key was not found instead of raising.

Returns:

The value associated with the key, if it was in the dictionary. If it wasn't, return the provided default value instead.

Raises:

"KeyError" if the key was not present in the dictionary and no default value was provided.

__iter__​

__iter__[mutability: i1, self_life: lifetime<*(0,0)>](self: !lit.ref<_stdlib::_collections::_dict::_Dict<:trait<_stdlib::_collections::_dict::_KeyElement> K, :trait<_stdlib::_builtin::_value::_CollectionElement> V>, mut=mutability, self_life>) -> _DictKeyIter[K, V, $0, $1, true]

Iterate over the dict's keys as immutable references.

Parameters:

  • ​mutability (i1): Whether the dict is mutable.
  • ​self_life (lifetime<*(0,0)>): The dict's lifetime.

Returns:

An iterator of immutable references to the dictionary keys.

keys​

keys[mutability: i1, self_life: lifetime<*(0,0)>](self: !lit.ref<_stdlib::_collections::_dict::_Dict<:trait<_stdlib::_collections::_dict::_KeyElement> K, :trait<_stdlib::_builtin::_value::_CollectionElement> V>, mut=mutability, self_life>) -> _DictKeyIter[K, V, $0, $1, true]

Iterate over the dict's keys as immutable references.

Parameters:

  • ​mutability (i1): Whether the dict is mutable.
  • ​self_life (lifetime<*(0,0)>): The dict's lifetime.

Returns:

An iterator of immutable references to the dictionary keys.

values​

values[mutability: i1, self_life: lifetime<*(0,0)>](self: !lit.ref<_stdlib::_collections::_dict::_Dict<:trait<_stdlib::_collections::_dict::_KeyElement> K, :trait<_stdlib::_builtin::_value::_CollectionElement> V>, mut=mutability, self_life>) -> _DictValueIter[K, V, $0, $1]

Iterate over the dict's values as references.

Parameters:

  • ​mutability (i1): Whether the dict is mutable.
  • ​self_life (lifetime<*(0,0)>): The dict's lifetime.

Returns:

An iterator of references to the dictionary values.

items​

items[mutability: i1, self_life: lifetime<*(0,0)>](self: !lit.ref<_stdlib::_collections::_dict::_Dict<:trait<_stdlib::_collections::_dict::_KeyElement> K, :trait<_stdlib::_builtin::_value::_CollectionElement> V>, mut=mutability, self_life>) -> _DictEntryIter[K, V, $0, $1, true]

Iterate over the dict's entries as immutable references.

These can't yet be unpacked like Python dict items, but you can access the key and value as attributes ie.

for e in dict.items():
    print(e[].key, e[].value)

Parameters:

  • ​mutability (i1): Whether the dict is mutable.
  • ​self_life (lifetime<*(0,0)>): The dict's lifetime.

Returns:

An iterator of immutable references to the dictionary entries.

update​

update(inout self: Self, other: Self, /)

Update the dictionary with the key/value pairs from other, overwriting existing keys. The argument must be positional only.

Args:

  • ​other (Self): The dictionary to update from.

__reversed__​

__reversed__[mutability: i1, self_life: lifetime<*(0,0)>](self: !lit.ref<_stdlib::_collections::_dict::_Dict<:trait<_stdlib::_collections::_dict::_KeyElement> K, :trait<_stdlib::_builtin::_value::_CollectionElement> V>, mut=mutability, self_life>) -> _DictKeyIter[K, V, $0, $1, false]

Iterate backwards over the dict keys, returning immutable references.

Returns:

A reversed iterator of immutable references to the dict keys.