render_set() vs. render_list()

render_set(<set_size>) was introduced in StringGenerator 0.4.2. It is an alternative to render_list().

render_list() takes an argument for a progress callback function and can generate a unique list if unique=True. It also throws an exception if you provide a pattern and result size that are not compatible, like:

SG("[123456789]{3}").render_list(800, unique=True)

The maximum number of unique results for this pattern is 729. An exception will be raised:

UniquenessError: couldn't satisfy uniqueness

In contrast, render_set() returns a set so it does not need a unique=True parameter. It is optimised to be fast and therefore does not support either a progress callback nor will it check if the request is feasible.

But it’s much faster than render_list(count, unique=True)

On a reasonably fast host, you can generate 100,000 unique 20 character strings in under five seconds:

In [5]: %time tokens = SG("[\w]{20}").render_set(100000)
CPU times: user 3.84 s, sys: 598 ms, total: 4.44 s
Wall time: 4.44 s

render_list(100000, unique=True) would accomplish the same thing but take well over 10x as long.

For much larger batches, the default random.SystemRandom becomes the bottleneck (a syscall per draw). If you need cryptographic security, pass SG.BufferedSecureRandom() as the randomizer for a large speedup; if you do not, seeding is faster still. See Seeding and Custom Randomization for the trade-offs.

The seed parameter has the same effect with render_set():

In [23]: SG(r"[\u\d]{46}", seed=100).render_set(10)
Out[23]:
{'1A2SM257I4JNSYABZHPJP4L0TS7YYY4H9IC6DB61YYOBHE',
'6SKXTOZ1CARF8GR148R9C5TLFF5N7FVJZ6CZV0L1PF2XAS',
'9DP6SV7V8X4ZDGT1QP165QJDUKDRHDOT7NWV3AH4M7HNCY',
'GZJ48C2KD4DMPKGCINFHQEZC8142V37MQ0JN0ERZQGMODY',
'H2BN7K4C82WAF5D1YJM1LNRQNSZZQVBRP7LD0FWHK4XN7P',
'HTIHODZ31WFEC20BJ4GFSG9JI9JKWYG5UH4SOWOCAO6H9F',
'I4D4W64N5D6QB77GLCO3AHOXUHTGTT2MUFKVJM1FFUNURJ',
'J33LZW16H8HF3QDNVOTNLJMWX0NZ39RYKHLAZJKMKBP2YI',
'RARTCB9SOZAFOTBFWU2CLFBW9JKAAU6ZLYY2MNK9RE3I16',
'ZB3VCQ5DEWCQ3S8ZXUKILV5Z0P5G7NLEPFBR4OV0CR4WVE'}

In [24]: SG(r"[\u\d]{46}", seed=100).render_set(10)
Out[24]:
{'1A2SM257I4JNSYABZHPJP4L0TS7YYY4H9IC6DB61YYOBHE',
'6SKXTOZ1CARF8GR148R9C5TLFF5N7FVJZ6CZV0L1PF2XAS',
'9DP6SV7V8X4ZDGT1QP165QJDUKDRHDOT7NWV3AH4M7HNCY',
'GZJ48C2KD4DMPKGCINFHQEZC8142V37MQ0JN0ERZQGMODY',
'H2BN7K4C82WAF5D1YJM1LNRQNSZZQVBRP7LD0FWHK4XN7P',
'HTIHODZ31WFEC20BJ4GFSG9JI9JKWYG5UH4SOWOCAO6H9F',
'I4D4W64N5D6QB77GLCO3AHOXUHTGTT2MUFKVJM1FFUNURJ',
'J33LZW16H8HF3QDNVOTNLJMWX0NZ39RYKHLAZJKMKBP2YI',
'RARTCB9SOZAFOTBFWU2CLFBW9JKAAU6ZLYY2MNK9RE3I16',
'ZB3VCQ5DEWCQ3S8ZXUKILV5Z0P5G7NLEPFBR4OV0CR4WVE'}