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If you compile a regex inside a function, and that function gets called multiple times, does Python recompile the regex each time, or does Python cache the compiled regex (assuming the regex doesn't change)?
For example:
def contains_text_of_interest(line):
r = re.compile(r"foo\dbar\d")
return r.match(line)
def parse_file(fname):
for line in open(fname):
if contains_text_of_interest(line):
# Do something interesting
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Basic usage In re. sub() , specify a regex pattern in the first argument, a new string in the second, and a string to be processed in the third. As with replace() , you can specify the maximum count of replacements in the fourth parameter, count . You can also create a regular expression pattern object with re.
sub() function belongs to the Regular Expressions ( re ) module in Python. It returns a string where all matching occurrences of the specified pattern are replaced by the replace string. To use this function, we need to import the re module first. import re.
The re. re. compile(pattern, repl, string): We can combine a regular expression pattern into pattern objects, which can be used for pattern matching. It also helps to search a pattern again without rewriting it.
Actually, if you look at the code in the re module, the re.compile function uses the cache just as all the other functions do, so compiling the same regex over and over again is very very cheap (a dictionary lookup). In other words, write the code to be the most understandable or maintainable or expressive, and don't worry about the overhead of compiling regexes.
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