So the performance advantage is minimal.Īll in all, there isn’t any immensely compelling reason to compile a regex in Python. The compiled value is fetched from cache instead. If the same regex is used subsequently in the same Python code, then it isn’t recompiled. The truth is that the re module compiles and caches a regex when it’s used in a function call. In practice, though, that isn’t the case. It might seem like compiling the regex once ahead of time would be more efficient than recompiling it each of the thousands of times it’s used. Suppose you call re.search() many thousands of times on the same regex. In theory, you might expect precompilation to result in faster execution time as well. ![]() If is a string, then re.sub() inserts it into in place of any sequences that match : can be either a string or a function, as explained below. Re.sub(,, ) finds the leftmost non-overlapping occurrences of in, replaces each match as indicated by, and returns the result. Returns a new string that results from performing replacements on a search string. (Remember that strings are immutable in Python, so it wouldn’t be possible for these functions to modify the original string.) Scans a string for regex matches, replaces the matching portions of the string with the specified replacement string, and returns the resultīehaves just like re.sub() but also returns information regarding the number of substitutions madeīoth re.sub() and re.subn() create a new string with the specified substitutions and return it. If you need that information, then re.finditer() will probably be the better choice. As you’ll see later in this tutorial, a lot of useful information can be obtained from a match object. Which one you choose will depend on the circumstances. The items in the list that re.findall() returns are the actual matching strings, whereas the items yielded by the iterator that re.finditer() returns are match objects.Īny task that you could accomplish with one, you could probably also manage with the other. Re.findall() returns a list, whereas re.finditer() returns an iterator. Re.findall() and re.finditer() are very similar, but they differ in two respects: finditer ( r '\w ', '.foo,bar:%$baz//|' ) > next ( it ) > next ( it ) > next ( it ) > next ( it ) Traceback (most recent call last):įile "", line 1, in StopIteration > for i in re.
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