How to read array of integer list stored in text file in Python?

Question

I wrote a text file that contains list of integers like below

cords = [[385, 24], [695, 32], [1010, 106], [1122, 245]]
f = open('ref_points.txt', 'w')
f.write(str(cords))
f.close()

I want to read back this text file and get the list of integers. I know when we read contents, it is str, and need processing to store in list. I would like to know if there is any better and efficient way of doing it.

Thanks

you should be able to use json.loads(string_content) with the content of your file. — Peterrabbit
– Peterrabbit, Commented Apr 21, 2022 at 10:14
As @Peterrabbit has correctly said, you could use the json module for this. However, in a more complex piece of code, anyone maintaining it might assume that the result would be a dictionary. For this case I would suggest ast.literal_eval() — jackal
– jackal, Commented Apr 21, 2022 at 10:41

Ontropy · Accepted Answer · 2022-04-21 10:23:24Z

1

You can use the pickle module and store the data as binary data, this way you have to not perform any type conversions. pickle already comes with python so you do not have to install anything either.

import pickle
coords = [[385, 24], [695, 32], [1010, 106], [1122, 245]]
f = open("points.bin", "wb")
pickle.dump(coords, f);
f.close();

# you can read it like this
f = open("points.bin", "wb")
coords = pickle.load(f) # here coords is a list so you do not have to convert anything
f.close()

also as @Marcin_Orlowski mentioned in the comments, a better way to open files will be to do so:

with open("somefile.txt") as f:
    # now you can use f for the file

this way you dont have to call f.close() either.

edited Apr 21, 2022 at 10:23

answered Apr 21, 2022 at 10:16

Ontropy

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3 Comments

Marcin Orlowski Over a year ago

pleaase use with to open the files, not the open/close which you do wrong anyway, due to lack of any error handling.

Ontropy Over a year ago

both ways are viable, I did open/close, because that is how the author approached it.

jackal Over a year ago

Using pickle is entirely correct - functionally. But what this technique doesn't account for is readability of the file which might be important.

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