Is there a difference between "+" and "{1,}" in regex?

Asked Aug 26 '19 at 16:19

Active Aug 26 '19 at 16:29

Viewed 46 times

I was learning about regex and found out that + and the {1,} have the same function. What I was wondering is whether there is any difference between the two?

I tried finding out the execution times by copying a standard passage and executing the regex patterns using the above two operators. I found out that the execution time for {1,} was faster than that of +. Can anyone explain why?

pattern1 = r'/[A-Z]{1,}/g'
pattern2 = r'/[A-Z]+/g'

edited Aug 26 '19 at 16:29

Barmar

741,623
53
500
612

asked Aug 26 '19 at 16:19

T.Square

1

`{1,}` = `+` unless it is BRE POSIX – Wiktor Stribiżew Aug 26 '19 at 16:29
2

Yes, they're equivalent. If the performance is different, it's a flaw in the RE engine. – Barmar Aug 26 '19 at 16:29
How much faster was it? – Barmar Aug 26 '19 at 16:31
thanks for the clarification :) {1,} took 4ms whereas + took 6ms – T.Square Aug 26 '19 at 16:33
1

@T.Square it seems like you are using Python. If so, I just ran `%timeit` from ipython and the mean time taken are `183 us` and `184 us`. If you're testing for time, make sure you're checking over multiple runs and using some timing mechanism that doesn't also time garbage collection, etc. – Chrispresso Aug 26 '19 at 16:36
@Chrispresso, I was just about to try taking the mean time. Thanks though :) – T.Square Aug 26 '19 at 16:38

Is there a difference between "+" and "{1,}" in regex?

0 Answers0