Convert list inside pandas dataframe to list variable

Question

I have a .csv file structured as well:

    chan_id   spacecraft                           anomaly_sequences
      P-1       SMAP                 [[2149, 2349], [4536, 4844], [3539, 3779]]

I need to convert the list of list inside the cell anomaly_sequences to a variable, so I can loop inside it. I did it so:

list_labels = df['anomaly_sequences'].values.tolist()

but it converted all the cell in a single list, in fact if I try to print it I see it as:

['[[2149, 2349], [4536, 4844], [3539, 3779]]']

How can I correct it?

@TomerS a list where its first element is [2149, 2349], its second element is [4536, 4844] etc.. — Fabio
– Fabio, Commented Oct 2, 2021 at 11:25
@Cimbali chan_id object spacecraft object anomaly_sequences object dtype: object — Fabio
– Fabio, Commented Oct 2, 2021 at 11:26
Hmmm I asked the wrong question, that doesn’t tell me if they’re strings or lists… If the objects are lists, df['anomaly_sequences'].explode() should work, if they are strings look at this recent question: stackoverflow.com/questions/69397259 , then do .explode() — Cimbali
– Cimbali, Commented Oct 2, 2021 at 11:27

Pascal G. Bernard · Accepted Answer · 2021-10-02 11:44:04Z

1

Not sure how you want to present your output, but if you want to convert your string into list of integers list, just do:

import json
var = "[[2149, 2349], [4536, 4844], [3539, 3779]]"
var = json.loads(var)
var

[[2149, 2349], [4536, 4844], [3539, 3779]]

And if you want to flatten the list of list, just use:

flat_list = [item for sublist in var for item in sublist]
flat_list

[2149, 2349, 4536, 4844, 3539, 3779]

answered Oct 2, 2021 at 11:36

Pascal G. Bernard

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