Dictionary¶
Dictionary type.
Description¶
Dictionary type. Associative container, which contains values referenced by unique keys. Dictionaries are composed of pairs of keys (which must be unique) and values. Dictionaries will preserve the insertion order when adding elements. In other programming languages, this data structure is sometimes referred to as a hash map or associative array.
You can define a dictionary by placing a comma-separated list of key: value pairs in curly braces {}.
Erasing elements while iterating over them is not supported and will result in undefined behavior.
Note: Dictionaries are always passed by reference. To get a copy of a dictionary which can be modified independently of the original dictionary, use duplicate.
Creating a dictionary:
var my_dict = {} # Creates an empty dictionary.
var dict_variable_key = "Another key name"
var dict_variable_value = "value2"
var another_dict = {
"Some key name": "value1",
dict_variable_key: dict_variable_value,
}
var points_dict = {"White": 50, "Yellow": 75, "Orange": 100}
# Alternative Lua-style syntax.
# Doesn't require quotes around keys, but only string constants can be used as key names.
# Additionally, key names must start with a letter or an underscore.
# Here, `some_key` is a string literal, not a variable!
another_dict = {
some_key = 42,
}
You can access a dictionary's values by referencing the appropriate key. In the above example, points_dict["White"] will return 50. You can also write points_dict.White, which is equivalent. However, you'll have to use the bracket syntax if the key you're accessing the dictionary with isn't a fixed string (such as a number or variable).
export(String, "White", "Yellow", "Orange") var my_color
var points_dict = {"White": 50, "Yellow": 75, "Orange": 100}
func _ready():
# We can't use dot syntax here as `my_color` is a variable.
var points = points_dict[my_color]
In the above code, points will be assigned the value that is paired with the appropriate color selected in my_color.
Dictionaries can contain more complex data:
my_dict = {"First Array": [1, 2, 3, 4]} # Assigns an Array to a String key.
To add a key to an existing dictionary, access it like an existing key and assign to it:
var points_dict = {"White": 50, "Yellow": 75, "Orange": 100}
points_dict["Blue"] = 150 # Add "Blue" as a key and assign 150 as its value.
Finally, dictionaries can contain different types of keys and values in the same dictionary:
# This is a valid dictionary.
# To access the string "Nested value" below, use `my_dict.sub_dict.sub_key` or `my_dict["sub_dict"]["sub_key"]`.
# Indexing styles can be mixed and matched depending on your needs.
var my_dict = {
"String Key": 5,
4: [1, 2, 3],
7: "Hello",
"sub_dict": {"sub_key": "Nested value"},
}
Note: Unlike Arrays, you can't compare dictionaries directly:
array1 = [1, 2, 3]
array2 = [1, 2, 3]
func compare_arrays():
print(array1 == array2) # Will print true.
var dict1 = {"a": 1, "b": 2, "c": 3}
var dict2 = {"a": 1, "b": 2, "c": 3}
func compare_dictionaries():
print(dict1 == dict2) # Will NOT print true.
You need to first calculate the dictionary's hash with hash before you can compare them:
var dict1 = {"a": 1, "b": 2, "c": 3}
var dict2 = {"a": 1, "b": 2, "c": 3}
func compare_dictionaries():
print(dict1.hash() == dict2.hash()) # Will print true.
Note: When declaring a dictionary with const, the dictionary itself can still be mutated by defining the values of individual keys. Using const will only prevent assigning the constant with another value after it was initialized.
Tutorials¶
Methods¶
void |
clear ( ) |
empty ( ) |
|
get_or_add ( Variant key, Variant default=null ) |
|
hash ( ) |
|
keys ( ) |
|
void |
merge ( Dictionary dictionary, bool overwrite=false ) |
size ( ) |
|
values ( ) |
Method Descriptions¶
void clear ( )
Clear the dictionary, removing all key/value pairs.
Dictionary duplicate ( bool deep=false )
Creates a copy of the dictionary, and returns it. The deep parameter causes inner dictionaries and arrays to be copied recursively, but does not apply to objects.
bool empty ( )
Returns true if the dictionary is empty.
Erase a dictionary key/value pair by key. Returns true if the given key was present in the dictionary, false otherwise.
Note: Don't erase elements while iterating over the dictionary. You can iterate over the keys array instead.
Variant find_key ( Variant value )
Returns the first key whose associated value is equal to value, or null if no such value is found.
Note: null is also a valid key. If you have it in your Dictionary, the find_key method can give misleading results.
Variant get ( Variant key, Variant default=null )
Returns the current value for the specified key in the Dictionary. If the key does not exist, the method returns the value of the optional default argument, or null if it is omitted.
Variant get_or_add ( Variant key, Variant default=null )
Gets a value and ensures the key is set. If the key exists in the dictionary, this behaves like get. Otherwise, the default value is inserted into the dictionary and returned.
Returns true if the dictionary has a given key.
Note: This is equivalent to using the in operator as follows:
# Will evaluate to `true`.
if "godot" in {"godot": "engine"}:
pass
This method (like the in operator) will evaluate to true as long as the key exists, even if the associated value is null.
Returns true if the dictionary has all the keys in the given array.
int hash ( )
Returns a hashed 32-bit integer value representing the dictionary contents. This can be used to compare dictionaries by value:
var dict1 = {0: 10}
var dict2 = {0: 10}
# The line below prints `true`, whereas it would have printed `false` if both variables were compared directly.
print(dict1.hash() == dict2.hash())
Note: Dictionaries with the same keys/values but in a different order will have a different hash.
Note: Dictionaries with equal content will always produce identical hash values. However, the reverse is not true. Returning identical hash values does not imply the dictionaries are equal, because different dictionaries can have identical hash values due to hash collisions.
Array keys ( )
Returns the list of keys in the Dictionary.
void merge ( Dictionary dictionary, bool overwrite=false )
Adds elements from dictionary to this Dictionary. By default, duplicate keys will not be copied over, unless overwrite is true.
int size ( )
Returns the number of keys in the dictionary.
Array values ( )
Returns the list of values in the Dictionary.