Fei Li Fei Li -4 years ago 179
Python Question

Python: read a file with lists converted to strings and convert back to lists

I have a txt file which looks like this:

0.41,"[1.0, 0.0, 1.0]","[16.4, 0.0, 0.0]"


0.23,"[0.0, 2.0, 2.0]","[32.8, 0.0, 0.0]"


0.19,"[0.0, 0.0, 3.0]","[92.8, 0.0, 0.0]"


and I hope to read it and convert the strings to lists:
a=[0.41, 0.23, 0.19, 0.03, 0.02, 0.02]


b=[[1.0, 0.0, 1.0],[0.0, 2.0, 2.0],[0.0, 0.0, 3.0]]


c=[[16.4, 0.0, 0.0],[32.8, 0.0, 0.0],[92.8, 0.0, 0.0]]


How can I do this in python?

Thanks in advance,

Fei

Answer Source

I would use csv module to properly tokenize the items, then I'd transpose the rows using zip and convert the string data to python lists/values using ast.literal_eval

import csv
import ast


with open("file.txt") as f:
   cr = csv.reader(f)
   items = [[ast.literal_eval(x) for x in row] for row in zip(*cr)]

print(items)

result: a list of lists

[[0.41, 0.23, 0.19], [[1.0, 0.0, 1.0], [0.0, 2.0, 2.0], [0.0, 0.0, 3.0]], [[16.4, 0.0, 0.0], [32.8, 0.0, 0.0], [92.8, 0.0, 0.0]]]

That's not the general case, but if you know you exactly have 3 items in the list, you can unpack them to any variables you want:

if len(items)==3:
    a,b,c = items
    print(a)
    print(b)
    print(c)

and you get:

[0.41, 0.23, 0.19]
[[1.0, 0.0, 1.0], [0.0, 2.0, 2.0], [0.0, 0.0, 3.0]]
[[16.4, 0.0, 0.0], [32.8, 0.0, 0.0], [92.8, 0.0, 0.0]]

note that your expected input is not possible for a given the input data.

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