Python 将包含列表元组的字符串解包为变量

Question

Hi guys I have been strugling how to unpack a string to varibles is a tuple with a list and a float.

model_parameters="('[None, False, None, 12, False, True]', 18.837459797657008)"

but the output i need must be in this form

output=[None, False, None, 12, False, True]
error=18.837459797657008
a,b,c,d,e,f=output

this is for load the statsmodels.tsa.holtwinters.ExponentialSmoothing with the grid searched model from https://machinelearningmastery.com/how-to-grid-search-triple-exponential-smoothing-for-time-series-forecasting-in-python/

Answer 1

you can do something like this:

import ast

def parse_tuple(string):
    try:
        s = ast.literal_eval(str(string))
        if type(s) == tuple:
            return s
        return
    except:
        return
t="('[None, False, None, 12, False, True]', 18.837459797657008)"
a=parse_tuple(t)
a=eval('[' + a[0] + ']')[0]

first, we define a function to convert your string to a tuple, after a=parse_tuple(t) , a[1] will be 18.837459797657008 , then we convert the other element to list, you can use a[i] to access values respectively.

Answer 2

You can use ast.literal_eval twice:

import ast

model_parameters="('[None, False, None, 12, False, True]', 18.837459797657008)"

list_as_str, error = ast.literal_eval(model_parameters)
output = ast.literal_eval(list_as_str)
a,b,c,d,e,f = output

# We have all the values we want:
print(a, b, c, d, e, f, error)
# None False None 12 False True 18.837459797657008

Answer 3

This is easiest for you using Python eval . Where the expression argument is parsed and evaluated as a Python expression

Look here:

model_parameters = "('[None, False, None, 12, False, True]', 18.837459797657008)"

m = eval(model_parameters)
output = eval(m[0])
error = m[1]
a, b, c, d, e, f = output

print(error)
print(a,b,c,d,e,f)

Outputs:

18.837459797657008
None False None 12 False True