How can I split text on commas while keeping commas inside quoted phrases?

A basic split uses each comma as a separator, without checking whether it appears inside quotes. Python’s re.split likewise splits at occurrences of its separator pattern; it does not automatically interpret CSV quoting. [S2]

For your example, a plain comma split would break London, UK into two pieces. The intended fields are Ada, London, UK, and editor. The key distinction is whether you have a deliberately simple string or a CSV record whose quoting rules need to be interpreted. A delimiter is just a character to a plain split; quote-aware parsing requires additional rules about where quoted fields begin and end.

If the input is one line, uses double quotes only to surround fields, and never has escaped quotes inside a field, you can split at commas that have an even number of double quotes to their right:

import re

text = 'Ada,"London, UK",editor'
fields = re.split(r',(?=(?:[^"]*"[^"]*")*[^"]*$)', text)
print(fields)

For that constrained example, the result is ['Ada', '"London, UK"', 'editor']; the quotes remain in the field. The lookahead checks the rest of the line for pairs of quotes, so the comma inside the quoted phrase is not treated as a separator.

This pattern is an illustration, not a general CSV parser. It relies on balanced, unescaped quotes and a simple one-line format. It does not establish that arbitrary CSV—or malformed input—will be parsed correctly. If your input can break any of those assumptions, don’t try to patch the pattern without first defining the format rules.

Use a CSV-aware reader rather than extending the regex. Python’s csv.reader reads records according to a dialect, including settings such as the delimiter and quote character; quoted fields can contain delimiters or newlines. Configure the reader for the actual CSV conventions you receive, since dialects and parser settings can vary. [S1]

For example, if text contains CSV data and the assumed dialect uses commas and double quotes:

import csv
from io import StringIO

text = 'Ada,"London, UK",editor\n'
rows = list(csv.reader(StringIO(text)))
print(rows[0])

This gives ['Ada', 'London, UK', 'editor'] for that example. If reading a file, pass the file object to csv.reader instead. Check the expected delimiter, quote character, and escaping conventions before relying on the result; this example does not determine the format of an unknown input. In particular, make sure the parser settings match the data producer’s dialect rather than assuming every CSV source uses identical conventions.