TypeError: Population must be a sequence. For dicts or sets, use sorted(d)

[harwoodr]

I'm getting this on one system running python 3.11.2, but the exact same code works fine on a system running python 3.10.12 - any thoughts?

[fengyangsun]

It seems you are sorting a population represented by a dict or set, something like "pop.sorted()", which is not allowed. It usually works for list or ndarray. For sorting dict or set, you should use "sorted (pop)".

[harwoodr]

Checked with a "print(type(pop))" and got "<class 'list'>"... as far as I can see, I don't believe I'm doing any sorting...

Also, as I said, it works fine on another system - I'm going to test on yet another system...

[fmder]

It would be easier to debug with minimal reproducing example posted in a gist or similar.

[harwoodr]

Easy - take https://github.com/DEAP/deap/blob/master/examples/gp/parity.py and replace:

toolbox.register("mate", gp.cxOnePoint)

with

toolbox.register("mate", gp.cxOnePointLeafBiased, termpb=0.1)

On my one system it works, no problem, on the other I get:

Traceback (most recent call last):
  File "/home/harwood/parity.py", line 92, in <module>
    main()
  File "/home/harwood/parity.py", line 87, in main
    algorithms.eaSimple(pop, toolbox, 0.5, 0.2, 40, stats, halloffame=hof)
  File "/home/harwood/.local/lib/python3.11/site-packages/deap/algorithms.py", line 168, in eaSimple
    offspring = varAnd(offspring, toolbox, cxpb, mutpb)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/harwood/.local/lib/python3.11/site-packages/deap/algorithms.py", line 73, in varAnd
    offspring[i - 1], offspring[i] = toolbox.mate(offspring[i - 1],
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/harwood/.local/lib/python3.11/site-packages/deap/gp.py", line 743, in cxOnePointLeafBiased
    type_ = random.sample(common_types, 1)[0]
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/random.py", line 439, in sample
    raise TypeError("Population must be a sequence.  "
TypeError: Population must be a sequence.  For dicts or sets, use sorted(d).

[harwoodr]

Further investigation says it may be a change in Python 3.11 that is to blame.

https://github.com/ray-project/ray/issues/36578#issuecomment-1599753193

[harwoodr]

Added https://github.com/DEAP/deap/pull/733 pull request with the very minor change to fix.

[fmder]

Thanks for debugging this! I'll check if any other place in the library needs to be changed and push to your branch.