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# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
UUID generation utilities.
"""
from __future__ import absolute_import # so we can import standard 'uuid'
from random import randrange
from uuid import uuid4
from shortuuid import ShortUUID
# Alphanumeric without visually ambiguous characters; default length is 22
UUID_BASE57 = ShortUUID()
# Lower-case alphanumeric; default length is 25
UUID_LOWERCASE_ALPHANUMERIC = ShortUUID(alphabet='abcdefghijklmnopqrstuvwxyz0123456789')
def generate_uuid(length=None, variant='base57'):
"""
A random string with varying degrees of guarantee of universal uniqueness.
:param variant:
* ``base57`` (the default) uses a mix of upper and lowercase alphanumerics ensuring no visually
ambiguous characters; default length 22
* ``alphanumeric`` uses lowercase alphanumeric; default length 25
* ``uuid`` uses lowercase hexadecimal in the classic UUID format, including dashes; length is
always 36
* ``hex`` uses lowercase hexadecimal characters but has no guarantee of uniqueness; default
length of 5
"""
if variant == 'base57':
the_id = UUID_BASE57.uuid()
if length is not None:
the_id = the_id[:length]
elif variant == 'alphanumeric':
the_id = UUID_LOWERCASE_ALPHANUMERIC.uuid()
if length is not None:
the_id = the_id[:length]
elif variant == 'uuid':
the_id = str(uuid4())
elif variant == 'hex':
length = length or 5
# See: http://stackoverflow.com/a/2782859
the_id = ('%0' + str(length) + 'x') % randrange(16 ** length)
else:
raise ValueError('unsupported UUID variant: {0}'.format(variant))
return the_id
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