Convert string representation of List to List in Python

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Borislav Hadzhiev

Last updated: Apr 9, 2024
5 min

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# Convert string representation of List to List in Python

Use the ast.literal_eval() method to convert the string representation of a list to a list.

The ast.literal_eval() method allows us to safely evaluate a string that contains a Python literal.

main.py
from ast import literal_eval

my_str = '[1,2,3,4]'

# ✅ convert string representation of list to list (ast.literal_eval())

my_list = literal_eval(my_str)
print(my_list)  # 👉️ [1, 2, 3, 4]
print(type(my_list))  # 👉️ <class 'list'>

convert string representation of list to list

The code for this article is available on GitHub

The example uses the ast.literal_eval() method to convert the string representation of a list to an actual list object.

The ast.literal_eval() method allows us to safely evaluate a string that contains a Python literal.

The string may consist of strings, bytes, numbers, tuples, lists, dicts, sets, booleans and None.

Alternatively, you can use the str.strip() method to remove the brackets.

# Convert string representation of List to List using strip()

This is a three-step process:

  1. Use the str.strip() method to remove the brackets.
  2. Split the string on each comma.
  3. Optionally, convert each list element to an integer.
main.py
my_str = '[1,2,3,4]'

my_list = [int(item) for item in my_str.strip('[]').split(',')]
print(my_list)  # 👉️ [1, 2, 3, 4]

convert string representation of list to list using strip

The code for this article is available on GitHub

The str.strip() method returns a copy of the string with the specified leading and trailing characters removed.

# Converting a String of quoted list elements to a List

If you have a string containing quoted elements, use the str.replace() method to remove the unnecessary quotes.

main.py
my_str = '["a", "b", "c"]'

my_list = my_str.strip('[]').replace('"', '').split(', ')
print(my_list)  # 👉️ ['a', 'b', 'c']
We used the str.replace() method to remove the double quotes from the string before calling the str.split() method.

# Converting a JSON string to a Python list

If you have a valid JSON string, you can also use the json.loads() method to convert the string representation of the list to a native Python list.

main.py
import json

my_str = '["a", "b", "c"]'

my_list = json.loads(my_str)

print(my_list)  # 👉️ ['a', 'b', 'c']
print(type(my_list))  # 👉️ <class 'list'>
The code for this article is available on GitHub

The json.loads() method parses a JSON string into a native Python object.

This approach also works for arrays containing numbers.

main.py
import json

my_str = '[1, 2, 3, 4]'

my_list = json.loads(my_str)

print(my_list)  # 👉️ [1, 2, 3, 4]
print(type(my_list))  # 👉️ <class 'list'>

If the data being parsed is not a valid JSON string, a JSONDecodeError is raised.

Note that this approach only works if you have a valid JSON string.

If there are nested strings wrapped in single quotes, this wouldn't work.

In that case, you should use the str.replace() method to remove the unnecessary quotes before splitting the string on each comma.

# Converting the string representation of a list to a list using re.findall()

You can also use the re.findall() method to convert the string representation of a list to a list.

main.py
import re

my_str = '[1, 2, 3, 4]'

list_of_strings = re.findall(r'[0-9]+', my_str)
print(list_of_strings) # 👉️ ['1', '2', '3', '4']

list_of_integers = [int(item) for item in list_of_strings]
print(list_of_integers) # 👉️ [1, 2, 3, 4]
The code for this article is available on GitHub

The same approach can be used if your list contains strings.

main.py
import re

my_str = '["ab", "cd", "ef", "gh"]'

list_of_strings = re.findall(r'\w+', my_str)
print(list_of_strings)  # 👉️ ['ab', 'cd', 'ef', 'gh']

The re.findall method takes a pattern and a string as arguments and returns a list of strings containing all non-overlapping matches of the pattern in the string.

If your list contains numbers, use the following regular expression.

main.py
import re

my_str = '[1, 2, 3, 4]'

list_of_strings = re.findall(r'[0-9]+', my_str)
print(list_of_strings) # 👉️ ['1', '2', '3', '4']

The square brackets [] are called a character class and match the digits in the specified range.

The plus + causes the regular expression to match 1 or more repetitions of the preceding character (the digits range).

The \w character matches:

  • characters that can be part of a word in any language
  • numbers
  • the underscore character

# Converting the string representation of a list to a list using eval()

You can also use the eval() function to convert the string representation of a list to a list.

main.py
my_str = '[1, 2, 3, 4]'

my_list = eval(my_str, {'__builtins__': None}, {})

print(my_list)  # 👉️ [1, 2, 3, 4]
print(type(my_list))  # 👉️ <class 'list'>
The code for this article is available on GitHub

However, note that using eval with user-supplied data isn't safe.

Instead, you should use the safer alternative - ast.literal_eval.

main.py
from ast import literal_eval

my_str = '[1,2,3,4]'

my_list = literal_eval(my_str)
print(my_list)  # 👉️ [1, 2, 3, 4]
print(type(my_list))  # 👉️ <class 'list'>

# Converting the string representation of a list to a list using map()

You can also use the map() function to convert the string representation of a list to a list.

main.py
my_str = '[1, 2, 3, 4]'

my_list = list(map(int, my_str[1:-1].split(',')))
print(my_list)  # 👉️ [1, 2, 3, 4]

If you have a list of strings, use the str.replace() method instead of map().

main.py
my_str = '["ab", "cd", "ef", "gh"]'

my_list = list(
    map(
        lambda x: x.replace('"', ''),
        my_str[1:-1].split(',')
    )
)
print(my_list)  # 👉️ [1, 2, 3, 4]
The code for this article is available on GitHub

We used string slicing to exclude the first and last characters from the string (the brackets) and split the string on each comma.

The map() function takes a function and an iterable as arguments and calls the function with each item of the iterable.

We passed the int() class to the map() function, so it gets called with each number from the list of strings.

The last step is to convert the map object to a list.

# Converting the string representation of a list to a list using PyYAML

You can also use the PyYAML module to convert the string representation of a list to a list.

First, make sure you have the PyYAML module installed by running the following command.

shell
pip install PyYAML

# 👇️ or with pip3

pip3 install PyYAML

Now you can import and use the PyYAML module.

main.py
import yaml

my_str = '[1, 2, 3, 4]'

my_list = yaml.safe_load(my_str)

print(my_list) # 👉️ [1, 2, 3, 4]

The PyYAML module can also be used if your list contains strings.

main.py
import yaml

my_str = '["ab", "cd", "ef", "gh"]'

my_list = yaml.safe_load(my_str)

print(my_list)  # 👉️ ['ab', 'cd', 'ef', 'gh']
The code for this article is available on GitHub

The yaml.safe_load() method loads a subset of the YAML language. This is recommended for loading untrusted input.

There is also a yaml_full_load method that you can use if you trust the data that's being parsed.

main.py
import yaml

my_str = '[1, 2, 3, 4]'

my_list = yaml.full_load(my_str)

print(my_list)  # 👉️ [1, 2, 3, 4]
The yaml.full_load() method takes a YAML document, parses it and produces the corresponding Python object.

Note that using the full_load() method with untrusted input is not recommended.

If you work with untrusted data, use the yaml.safe_load() method instead.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

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