utils

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

cipher

class eventsourcing.utils.cipher.aes.AESCipher(cipher_key)

Bases: object

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

__init__(cipher_key)

Initialises AES cipher strategy with cipher_key.

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

encrypt(plaintext)

Return ciphertext for given plaintext.

decrypt(ciphertext)

Return plaintext for given ciphertext.

times

eventsourcing.utils.times.decimaltimestamp_from_uuid(uuid_arg)

Return a floating point unix timestamp.

Parameters:uuid_arg – Returns:Unix timestamp in seconds, with microsecond precision. Return type:float

eventsourcing.utils.times.timestamp_long_from_uuid(uuid_arg)

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

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

eventsourcing.utils.times.decimaltimestamp(t=None)

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)

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)

Returns a string describing a class.

Args:

domain_class: A class.

Returns:

A string describing the class.

eventsourcing.utils.topic.resolve_topic(topic)

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, path)

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

class eventsourcing.utils.transcoding.ObjectJSONEncoder(sort_keys=True, *args, **kwargs)

Bases: json.encoder.JSONEncoder

__init__(sort_keys=True, *args, **kwargs)

Constructor for JSONEncoder, with sensible defaults.

If skipkeys is false, then it is a TypeError to attempt encoding of keys that are not str, int, float or None. If skipkeys is True, such items are simply skipped.

If ensure_ascii is true, the output is guaranteed to be str objects with all incoming non-ASCII characters escaped. If ensure_ascii is false, the output can contain non-ASCII characters.

If check_circular is true, then lists, dicts, and custom encoded objects will be checked for circular references during encoding to prevent an infinite recursion (which would cause an OverflowError). Otherwise, no such check takes place.

If allow_nan is true, then NaN, Infinity, and -Infinity will be encoded as such. This behavior is not JSON specification compliant, but is consistent with most JavaScript based encoders and decoders. Otherwise, it will be a ValueError to encode such floats.

If sort_keys is true, then the output of dictionaries will be sorted by key; this is useful for regression tests to ensure that JSON serializations can be compared on a day-to-day basis.

If indent is a non-negative integer, then JSON array elements and object members will be pretty-printed with that indent level. An indent level of 0 will only insert newlines. None is the most compact representation.

If specified, separators should be an (item_separator, key_separator) tuple. The default is (‘, ‘, ‘: ‘) if indent is None and (‘,’, ‘: ‘) otherwise. To get the most compact JSON representation, you should specify (‘,’, ‘:’) to eliminate whitespace.

If specified, default is a function that gets called for objects that can’t otherwise be serialized. It should return a JSON encodable version of the object or raise a TypeError.

iterencode(o, _one_shot=False)

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

For example:

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

default(obj)

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)

class eventsourcing.utils.transcoding.ObjectJSONDecoder(object_hook=None, **kwargs)

Bases: json.decoder.JSONDecoder

__init__(object_hook=None, **kwargs)

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.encode_random_bytes(num_bytes)

Generates random bytes, encoded as Base64 unicode string.

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

eventsourcing.utils.random.random_bytes(num_bytes)

Generates random bytes.

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

eventsourcing.utils.random.encode_bytes(bytes)

Encodes bytes as Base64 unicode string.

eventsourcing.utils.random.decode_bytes(s)

Decodes bytes from Base64 encoded unicode string.

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