Reference · Regular expressions

re.split

re.split(str, str, str | null=) -> list

What it does

The text cut at every match of a pattern, as a list of the pieces between the matches. The matches themselves are left out. Where the separator is plain text, split does the same without a pattern. The flags come last: "i", "m", "s".

Examples

print(re.split("a, b,c ,  d", "\\s*,\\s*"))print(re.split("a1b22c", "\\d+"))print(re.split("one\ntwo\r\nthree", "\\r?\\n"))print(re.split("k1=v1;k2=v2", "[;=]"))

["a", "b", "c", "d"]["a", "b", "c"]["one", "two", "three"]["k1", "v1", "k2", "v2"]

Edge cases

• Empty pieces are kept: a match at the start, at the end or twice in a row gives "" there.
• A pattern that matches nothing gives the whole text as the only piece; the empty text gives [""].
• Groups in the pattern are not put into the list, unlike JavaScript's split.
• The empty pattern cuts between every two characters, with "" at both ends; a pattern that can match the empty text (a*) gives empty pieces where it does.
• Characters, not bytes: "añb" cut at ñ is ["a", "b"].

print(re.split(",a,,b,", ","), re.split("x", "x"))print(re.split("abc", "x"), re.split("", "x"))print(re.split("a1b", "(\\d)"), re.split("A-b_C", "[-_]", "i"))print(re.split("ab", ""), re.split("aaa", "a*"))print(re.split("añb", "ñ"))

["", "a", "", "b", ""] ["", ""]["abc"] [""]["a", "b"] ["A", "b", "C"]["", "a", "b", ""] ["", "", ""]["a", "b"]

Errors

A pattern that is not supported (lookaround, backreferences, \p{...}, a bad escape, a bad flag) is a runtime error, not an error value, as is a text that is not a string. See re.test for what a pattern may hold.

print(re.split("abc", "(?!b)"))

line 1: `re.split`: lookahead and lookbehind ((?= (?! (?<= (?<!) are not supported

print(re.split(42, ","))

line 1: `re.split` expects a str as argument 1, got int

Chaining

The text comes first in a pipeline, and the pieces go on to map or filter:

print("a  b   c" | re.split("\\s+") | map(upper))print("one, two,,three" | re.split("\\s*,\\s*") | filter((p) => p != ""))let [key, value] = re.split("name = Ann", "\\s*=\\s*")print(key, value)

["A", "B", "C"]["one", "two", "three"]name Ann

See also

split, re.find_all, re.replace, join, filter

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