{"id":2627,"date":"2020-01-17T18:35:53","date_gmt":"2020-01-17T18:35:53","guid":{"rendered":"https:\/\/www.askpython.com\/?p=2627"},"modified":"2021-06-21T07:31:12","modified_gmt":"2021-06-21T07:31:12","slug":"python-convert-string-to-list","status":"publish","type":"post","link":"https:\/\/www.askpython.com\/python\/string\/python-convert-string-to-list","title":{"rendered":"Python – Convert String to List"},"content":{"rendered":"\n

In Python, if you ever need to deal with codebases that perform various calls to other APIs, there may be situations where you may receive a string in a list-like format, but still not explicitly a list. In situations like these, you may want to convert the string into a list. <\/p>\n\n\n\n

In this article, we will look at some ways of achieving the same on Python.<\/p>\n\n\n\n

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Converting List-type strings<\/h2>\n\n\n\n

A list-type<\/em> string can be a string that has the opening and closing parenthesis as of a list and has comma-separated characters for the list elements. The only difference between that and a list is the opening and closing quotes, which signify that it is a string.<\/p>\n\n\n\n

Example:<\/p>\n\n\n

\nstr_inp = '["Hello", "from", "AskPython"]'\n<\/pre><\/div>\n\n\n
Let us look at how we can convert these types of strings to a list.<\/p>\n\n\n\n
Method 1: Using the ast module<\/h3>\n\n\n\n
Python’s ast<\/code> (Abstract Syntax Tree) module is a handy tool that can be used to deal with strings like this, dealing with the contents of the given string accordingly.<\/p>\n\n\n\n
We can use ast.literal_eval()<\/code> to evaluate the literal and convert it into a list.<\/p>\n\n\n
\nimport ast\n\nstr_inp = '["Hello", "from", "AskPython"]'\nprint(str_inp)\nop = ast.literal_eval(str_inp)\nprint(op)\n<\/pre><\/div>\n\n\n
Output<\/strong><\/p>\n\n\n
\n'["Hello", "from", "AskPython"]'\n['Hello', 'from', 'AskPython']\n<\/pre><\/div>\n\n\n
Method 2: Using the json module<\/h3>\n\n\n\n
Python’s json<\/code> module also provides us with methods that can manipulate strings.<\/p>\n\n\n\n
In particular, the json.loads()<\/code> method is used to decode JSON-type strings and returns a list, which we can then use accordingly.<\/p>\n\n\n
\nimport json\n\nstr_inp = '["Hello", "from", "AskPython"]'\nprint(str_inp)\nop = json.loads(str_inp)\nprint(op)\n<\/pre><\/div>\n\n\n
The output remains the same as before.<\/p>\n\n\n\n
Method 3: Using str.replace() and str.split()<\/h3>\n\n\n\n
We can use Python’s in-built str.replace()<\/code> method and manually iterate through the input string.<\/p>\n\n\n\n
We can remove the opening and closing parenthesis while adding elements to our newly formed list using str.split(\",\")<\/code>, parsing the list-type string manually.<\/p>\n\n\n
\nstr_inp = '["Hello", "from", "AskPython"]'\nstr1 = str_inp.replace(']','').replace('[','')\nop = str1.replace('"','').split(",")\nprint(op)\n<\/pre><\/div>\n\n\n
Output<\/strong>:<\/p>\n\n\n
\n['Hello', ' from', ' AskPython']\n<\/pre><\/div>\n\n\n
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Converting Comma separated Strings<\/h2>\n\n\n\n
A comma-separated string is a string that<\/em> has a sequence of characters, separated by a comma, and enclosed in Python’s string quotations.<\/p>\n\n\n\n
Example:<\/p>\n\n\n
\nstr_inp = "Hello,from,AskPython'\n<\/pre><\/div>\n\n\n
To convert these types of strings to a list of elements, we have some other ways of performing the task.<\/p>\n\n\n\n
Method 1: Using str.split(‘,’)<\/h3>\n\n\n\n
We can directly convert it into a list by separating out the commas using str.split(',')<\/code>.<\/p>\n\n\n
\nstr_inp = "Hello,from,AskPython"\nop = str_inp.split(",")\nprint(op)\n<\/pre><\/div>\n\n\n
Output<\/strong>:<\/p>\n\n\n
\n['Hello', 'from', 'AskPython']\n<\/pre><\/div>\n\n\n
Method 2: Using eval()<\/h3>\n\n\n\n
If the input string is trusted, we can spin up an interactive shell and directly evaluate the string using eval()<\/code>.<\/p>\n\n\n\n
However, this is NOT<\/strong> recommended, and should rather be avoided, due to security hazards of running potentially untrusted code.<\/p>\n\n\n\n
Even so, if you still want to use this, go ahead. We warned you!<\/p>\n\n\n
\nstr_inp = "potentially,untrusted,code"\n\n# Convert to a quoted string so that\n# we can use eval() to convert it into\n# a normal string\nstr_inp = "'" + str_inp + "'"\nstr_eval = ''\n\n# Enclose every comma within single quotes\n# so that eval() can separate them\nfor i in str_inp:\n    if i == ',':\n        i = "','"\n    str_eval += i\n\nop = eval('[' + str_eval + ']')\nprint(op)\n<\/pre><\/div>\n\n\n
The output will be a list, since the string has been evaluated and a parenthesis has been inserted to now signify that it op<\/code> is a list.<\/p>\n\n\n\n
Output<\/strong><\/p>\n\n\n
\n['potentially', 'untrusted', 'code']\n<\/pre><\/div>\n\n\n
This is quite long and is not recommended for parsing out comma-separated strings. Using str.split(',')<\/code> is the obvious choice in this case.<\/p>\n\n\n\n
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Conclusion<\/h2>\n\n\n\n
In this article, we learned some ways of converting a list into a string. We dealt with list-type strings and comma-separated strings and converted them into Python lists.<\/p>\n\n\n\n
References<\/h2>\n\n\n\n