打印具有类型的对象中的特定值<class 'str'>

Question

I am running a grid search to obtain the optimal parameters for my Holt-Winters model.

My problem isn't with this, but from splitting the output.

# grid search configs
def grid_search(data, cfg_list, n_test, parallel=False):
scores = None
    if parallel:
        # execute configs in parallel
        executor = Parallel(n_jobs=cpu_count(), backend='multiprocessing')
        tasks = (delayed(score_model)(data, n_test, cfg) for cfg in cfg_list)
        scores = executor(tasks)
    else:
        scores = [score_model(data, n_test, cfg) for cfg in cfg_list]
    # remove empty results
    scores = [r for r in scores if r[1] != None]
    # sort configs by error, asc
    scores.sort(key=lambda tup: tup[1])
    return scores

if __name__ == '__main__':
    # load dataset
    data = series.values
    # data split
    n_test = 6
    # model configs
    cfg_list = exp_smoothing_configs(seasonal=[12])
    # grid search
    scores = grid_search(data, cfg_list, n_test)

    print('done')
    # list top 3 configs
    for cfg, error in scores[:3]:
        print(cfg, error)


c=scores[0][0]
print(c)
[None, False, 'add', 12, True, False]

print(type(c))
<class 'str'>

scores looks like this:

print(scores)
[("[None, False, 'add', 12, True, False]", 77287.30870008223), ("[None, False, 'add', 12, True, True]", 82358.18290862873), ("[None, False, 'add', 12, False, False]", 89424.13093850421), ("[None, False, 'add', 12, False, True]", 92702.59197070534), ("[None, False, 'mul', 12, False, False]", 138889.51422419012), ("[None, False, 'mul', 12, False, True]", 143041.76605824768), ("[None, False, 'mul', 12, True, False]", 151094.71387298577), ("[None, False, 'mul', 12, True, True]", 155234.18460656865), ("['add', False, None, 12, True, False]", 286472.4116758029), ("['add', False, None, 12, True, True]", 287519.4400580368), ("['add', True, None, 12, True, False]", 290043.11385268555), ("['add', True, None, 12, True, True]", 291097.96863945096), ("['add', False, None, 12, False, True]", 293015.5612969006), ("['add', False, None, 12, False, False]", 294728.0244142087), ("['mul', False, None, 12, True, True]", 298744.59053811635), ("['add', True, None, 12, False, True]", 298773.6174892717), ("['mul', False, None, 12, False, False]", 299016.44699124835), ("['add', True, None, 12, False, False]", 301282.3881674402), ("['mul', False, None, 12, False, True]", 301539.4816286923), ("['mul', False, None, 12, True, False]", 305131.0375033285), ('[None, False, None, 12, False, False]', 305753.8289179507), ("['mul', True, None, 12, True, True]", 307790.8943120729), ("['mul', True, None, 12, True, False]", 312108.27495445166), ('[None, False, None, 12, True, False]', 313635.56832930725), ('[None, False, None, 12, False, True]', 313762.349260778), ("['mul', True, None, 12, False, True]", 315240.5397127802), ('[None, False, None, 12, True, True]', 315930.0729960225), ("['mul', True, None, 12, False, False]", 319352.33996587264)]

How I can print out the first entry (which is None)? When I print c[0], the output is [.

Answer 1

If your strings are guaranteed to be python literals then you can use ast.literal_eval :

import ast

c = "[None, False, 'add', 12, True, False]"

assert ast.literal_eval(c)[0] is None
assert ast.literal_eval(c)[2] == 'add'
assert ast.literal_eval(c)[3] == 12

This should solve the problem as stated in the question.

But something does not feel right here. Why is score_model returning those strings instead of just lists? You might want to take a look at that instead of solving a problem that probably sould not extist in the first place.