utils¶

The utils package contains common functions that are used in more than one layer.

cipher¶

class eventsourcing.utils.cipher.aes.AESCipher(cipher_key: bytes)[source]¶

Bases: object

Cipher strategy that uses Crypto library AES cipher in GCM mode.

__init__(cipher_key: bytes)[source]¶

Initialises AES cipher strategy with cipher_key.

Parameters:	cipher_key – 16, 24, or 32 random bytes

encrypt(plaintext: bytes) → bytes[source]¶: Return ciphertext for given plaintext.

decrypt(ciphertext: bytes) → bytes[source]¶: Return plaintext for given ciphertext.

times¶

eventsourcing.utils.times.decimaltimestamp_from_uuid(value: uuid.UUID) → decimal.Decimal[source]¶

Return a floating point unix timestamp from UUID value.

Parameters:	value –
Returns:	Unix timestamp in seconds, with microsecond precision.
Return type:	Decimal

eventsourcing.utils.times.timestamp_long_from_uuid(value: uuid.UUID) → int[source]¶

Returns an integer value representing a unix timestamp in tenths of microseconds.

Parameters:	value –
Returns:	Unix timestamp integer in tenths of microseconds.
Return type:	int

eventsourcing.utils.times.decimaltimestamp(t: Optional[float] = None) → decimal.Decimal[source]¶

A UNIX timestamp as a Decimal object (exact number type).

Returns current time when called without args, otherwise converts given floating point number t to a Decimal with 9 decimal places.

Parameters:	t – Floating point UNIX timestamp (“seconds since epoch”).
Returns:	A Decimal with 6 decimal places, representing the given floating point or the value returned by time.time().
Return type:	Decimal

eventsourcing.utils.times.datetime_from_timestamp(t: Union[decimal.Decimal, float]) → datetime.datetime[source]¶

Returns naive UTC datetime from decimal UNIX timestamps such as time.time().

Parameters:	t – timestamp, either Decimal or float
Returns:	datetime.datetime object

topic¶

eventsourcing.utils.topic.get_topic(domain_class: type) → str[source]¶

Returns a string describing a class.

Args:: domain_class: A class.
Returns:: A string describing the class.

eventsourcing.utils.topic.resolve_topic(topic: str) → Any[source]¶

Return class described by given topic.

Args:: topic: A string describing a class.
Returns:: A class.
Raises:: TopicResolutionError: If there is no such class.

eventsourcing.utils.topic.resolve_attr(obj: Any, path: str) → Any[source]¶

A recursive version of getattr for navigating dotted paths.

Args:: obj: An object for which we want to retrieve a nested attribute. path: A dot separated string containing zero or more attribute names.
Returns:: The attribute referred to by obj.a1.a2.a3…
Raises:: AttributeError: If there is no such attribute.

transcoding¶

eventsourcing.utils.transcoding.encoderpolicy(arg=None)[source]¶

Decorator for encoder policy.

Allows default behaviour to be built up from methods registered for different types of things, rather than chain of isinstance() calls in a long if-else block.

eventsourcing.utils.transcoding.decoderpolicy(arg=None)[source]¶

Decorator for decoder policy.

Allows default behaviour to be built up from methods registered for different named keys, rather than chain of “in dict” queries in a long if-else block.

class eventsourcing.utils.transcoding.ObjectJSONEncoder(*, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, sort_keys=False, indent=None, separators=None, default=None)[source]¶

Bases: json.encoder.JSONEncoder

iterencode(o, _one_shot=False)[source]¶

Encode the given object and yield each string representation as available.

For example:

for chunk in JSONEncoder().iterencode(bigobject):
    mysocket.write(chunk)

default(obj)[source]¶

Implement this method in a subclass such that it returns a serializable object for o, or calls the base implementation (to raise a TypeError).

For example, to support arbitrary iterators, you could implement default like this:

def default(self, o):
    try:
        iterable = iter(o)
    except TypeError:
        pass
    else:
        return list(iterable)
    # Let the base class default method raise the TypeError
    return JSONEncoder.default(self, o)

exception eventsourcing.utils.transcoding.EncoderTypeError[source]¶: Bases: TypeError

class eventsourcing.utils.transcoding.ObjectJSONDecoder(object_hook=None, **kwargs)[source]¶

Bases: json.decoder.JSONDecoder

__init__(object_hook=None, **kwargs)[source]¶

object_hook, if specified, will be called with the result of every JSON object decoded and its return value will be used in place of the given dict. This can be used to provide custom deserializations (e.g. to support JSON-RPC class hinting).

object_pairs_hook, if specified will be called with the result of every JSON object decoded with an ordered list of pairs. The return value of object_pairs_hook will be used instead of the dict. This feature can be used to implement custom decoders. If object_hook is also defined, the object_pairs_hook takes priority.

parse_float, if specified, will be called with the string of every JSON float to be decoded. By default this is equivalent to float(num_str). This can be used to use another datatype or parser for JSON floats (e.g. decimal.Decimal).

parse_int, if specified, will be called with the string of every JSON int to be decoded. By default this is equivalent to int(num_str). This can be used to use another datatype or parser for JSON integers (e.g. float).

parse_constant, if specified, will be called with one of the following strings: -Infinity, Infinity, NaN. This can be used to raise an exception if invalid JSON numbers are encountered.

If strict is false (true is the default), then control characters will be allowed inside strings. Control characters in this context are those with character codes in the 0-31 range, including '\t' (tab), '\n', '\r' and '\0'.

random¶

eventsourcing.utils.random.encoded_random_bytes(num_bytes: int) → str[source]¶

Generates random bytes, encoded as Base64 unicode string.

Parameters:	num_bytes – Number of random bytes to generate.
Returns:	Random bytes of specified length, encoded as Base64 unicode string.

eventsourcing.utils.random.encode_random_bytes(num_bytes: int) → str¶

Generates random bytes, encoded as Base64 unicode string.

Parameters:	num_bytes – Number of random bytes to generate.
Returns:	Random bytes of specified length, encoded as Base64 unicode string.

eventsourcing.utils.random.random_bytes(num_bytes: int) → bytes[source]¶

Generates random bytes.

Parameters:	num_bytes – Number of random bytes to generate.
Returns:	Random bytes of specified length.
Type:	bytes

eventsourcing.utils.random.encode_bytes(value: bytes) → str[source]¶

Encodes value as Base64 unicode string.

Parameters:	value – Bytes to be encoded.

eventsourcing.utils.random.decode_bytes(value: str) → bytes[source]¶

Decodes bytes from Base64 encoded unicode string.

Parameters:	value (str) – Base64 string.
Returns:	Bytes that were encoded with Base64.
Return type:	bytes