Convert string of lists into list of lists in Python

Question

I'm trying to convert a list of lists passed as string to nested list in python-3.7.5 and I'm missing something. I tried ast but it seems to be throwing an encoding error.

Example:

#!/usr/bin/env python

import ast
sample="[1abcd245,2bcdasdf,3jakdshfkh234234],[234asdfmnkk234]"
print(ast.literal_eval(sample))

ERROR:

    return compile(source, filename, mode, PyCF_ONLY_AST)
  File "<unknown>", line 1
    [1abcd245,2bcdasdf,3jakdshfkh234234],[234asdfmnkk234]

Required output:
[[1abcd245,2bcdasdf,3jakdshfkh234234],[234asdfmnkk234]]

Any suggestions?

Tim Biegeleisen · Accepted Answer · 2021-04-30 05:29:00Z

2

You may use the eval() function here, after making two changes to your starting string:

Wrap each list item in double quotes
Wrap the entire input in [...] to make it a formal 2D list

sample = "[1abcd245,2bcdasdf,3jakdshfkh234234],[234asdfmnkk234]"
sample = '[' + re.sub(r'(\w+)', r'"\1"', sample) + ']'
list = eval(sample)
print(list)

This prints:

[['1abcd245', '2bcdasdf', '3jakdshfkh234234'], ['234asdfmnkk234']]

answered Apr 30, 2021 at 5:29

Tim Biegeleisen

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1 Comment

Jason Over a year ago

Feels like your answer is the closest I could get. Was hoping ast might have solution for this.

Bernstern · Accepted Answer · 2021-04-30 05:47:18Z

2

I think the issue is that literal_eval is unable to parse the strings within the sample you provide. I was able to get the output you wanted by adding a triple quote to surround the sample string, adding quotes to each string within the lists and adding an extra set of brackets:

import ast
sample="""[["1abcd245","2bcdasdf","3jakdshfkh234234"],["234asdfmnkk234"]]"""
print(ast.literal_eval(sample))

In the case you cannot change the input I would recommend using the json library:

import json
json.loads(sample)

Which on my machine gets the desired result!

edited Apr 30, 2021 at 5:47

answered Apr 30, 2021 at 5:28

Bernstern

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3 Comments

Jason Over a year ago

I cannot change the input, here.

Jason Over a year ago

if sample= "[1abcd245,2bcdasdf,3jakdshfkh234234],[234asdfmnkk234]", then json.loads also errors out. Error:

File "python-3.7.5/lib/python3.7/json/__init__.py", line 348, in loads     return _default_decoder.decode(s)   File "python-3.7.5/lib/python3.7/json/decoder.py", line 337, in decode     obj, end = self.raw_decode(s, idx=_w(s, 0).end())   File "python-3.7.5/lib/python3.7/json/decoder.py", line 353, in raw_decode     obj, end = self.scan_once(s, idx) json.decoder.JSONDecodeError: Expecting ',' delimiter: line 1 column 3 (char 2)

Bernstern Over a year ago

I see, that's my bad I was using the altered version of the input, why are you unable to modify the input?

Amit Nanaware · Accepted Answer · 2021-04-30 05:34:11Z

0

you can try this:

sample="[1abcd245,2bcdasdf,3jakdshfkh234234],[234asdfmnkk234]"
l1 = []
for item in sample.split(","):
    if item.startswith('['):
        l1.append([])
        l1[-1].append(item[1:])
    elif item.endswith(']'):
        l1[-1].append(item[:-2])
    else:
        l1[-1].append(item)


print(l1)

answered Apr 30, 2021 at 5:34

Amit Nanaware

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