storage

Gets current storage context.

>>> get_context()       # StorageContext cannot be read outside the blockchain
_InteropInterface

Returns:: the current storage context
Return type:: StorageContext

get(key: bytes, context: Optional[StorageContext] = None) → bytes

Gets a value from the persistent store based on the given key.

>>> put(b'unit', 'test')
... get(b'unit')
'test'

>>> get(b'fake_key')
''

Parameters:

key (bytes) – value identifier in the store
context (StorageContext) – storage context to be used

Returns:

the value corresponding to given key for current storage context

Return type:

bytes

get_read_only_context() → StorageContext

Gets current read only storage context.

>>> get_context()       # StorageContext cannot be read outside the blockchain
_InteropInterface

Returns:: the current read only storage context
Return type:: StorageContext

put(key: bytes, value: Union[int, bytes, str], context: Optional[StorageContext] = None)

Inserts a given value in the key-value format into the persistent storage.

>>> put(b'unit', 'test')
None

Parameters:

key (bytes) – the identifier in the store for the new value
value (int or str or bytes) – value to be stored
context (StorageContext) – storage context to be used

delete(key: bytes, context: Optional[StorageContext] = None)

Removes a given key from the persistent storage if exists.

>>> put(b'unit', 'test')
... delete()
... get(b'unit')
''

Parameters:

key (bytes) – the identifier in the store for the new value
context (StorageContext) – storage context to be used

find(prefix: bytes, context: Optional[StorageContext] = None, options: FindOptions = FindOptions.NONE) → Iterator

Searches in the storage for keys that start with the given prefix.

>>> put(b'a1', 'one')
... put(b'a2', 'two')
... put(b'a3', 'three')
... put(b'b4', 'four')
... findIterator = find(b'a')
... findResults = []
... while findIterator.next():
...     findResults.append(findIterator.value)
... findResults
['one', 'two', 'three']

Parameters:

prefix (bytes) – prefix to find the storage keys
context (StorageContext) – storage context to be used
options (FindOptions) – the options of the search

Returns:

an iterator with the search results

Return type:

Iterator

Subpackages

class FindOptions(value)

Bases: IntEnum

Represents the options you can use when trying to find a set of values inside the storage.

Check out Neo’s Documentation to learn more about the FindOption class.

NONE

No option is set. The results will be an iterator of (key, value).

KEYS_ONLY

Indicates that only keys need to be returned. The results will be an iterator of keys.

REMOVE_PREFIX

Indicates that the prefix byte of keys should be removed before return.

VALUES_ONLY

Indicates that only values need to be returned. The results will be an iterator of values.

DESERIALIZE_VALUES

Indicates that values should be deserialized before return.

PICK_FIELD_0

Indicates that only the field 0 of the deserialized values need to be returned. This flag must be set together with DESERIALIZE_VALUES, e.g., DESERIALIZE_VALUES | PICK_FIELD_0

PICK_FIELD_1

Indicates that only the field 1 of the deserialized values need to be returned. This flag must be set together with DESERIALIZE_VALUES, e.g., DESERIALIZE_VALUES | PICK_FIELD_1

BACKWARDS

Indicates that results should be returned in backwards (descending) order.

class StorageContext

Bases: object

The storage context used to read and write data in smart contracts.

Check out Neo’s Documentation to learn more about the StorageContext class.

create_map(prefix: bytes) → StorageMap

Creates a storage map with the given prefix.

Parameters:: prefix (bytes) – the identifier of the storage map
Returns:: a map with the key-values in the storage that match with the given prefix
Return type:: StorageMap

as_read_only() → StorageContext

Converts the specified storage context to a new readonly storage context.

Returns:: current StorageContext as ReadOnly
Return type:: StorageContext

class StorageMap(context, prefix: bytes)

Bases: object

The key-value storage for the specific prefix in the given storage context.

Check out Neo’s Documentation to learn more about StorageMap.

get(key: bytes) → bytes

Gets a value from the map based on the given key.

Parameters:: key (bytes) – value identifier in the store
Returns:: the value corresponding to given key for current storage context
Return type:: bytes

put(key: bytes, value: Union[int, bytes, str])

Inserts a given value in the key-value format into the map.

Parameters:

key (bytes) – the identifier in the store for the new value
value (int or str or bytes) – value to be stored

delete(key: bytes)

Removes a given key from the map if exists.

Parameters:: key (bytes) – the identifier in the store for the new value