from datetime import datetime
import re


"""
Brief summary:

Seems to be an expression consuming o(c^n) CPU cycles with c around 2.

Regex:
(\*([^*]+)*\*)

Seems to behave the same way without the parentheses. 

Evaluated with stuffing "* is there anybody out?" with digits.
 
Resulted in times (in seconds) of 

0.17   (* is there anybody out?)
0.34 1
0.69 12
1.36 123
2.73  1234
5.44  12345
11.1  123456  (* is there anybody123456 out?)

(Inaccurate single run/repeat measurements, with a warmed up CPU, but the trend 
seems clear. Used Python 3.8.10, x64, Linux build.

Same goes to trying this in PyCharm 3.7.something to search for the regex in a
text file that contains that very line :) )
"""

def test_match(expr, text, multiline:bool=True):
    flags = 0
    if multiline:
        flags = re.MULTILINE

    start = datetime.utcnow()
    match = re.match(expr, text, flags=flags)
    print("Took ", (datetime.utcnow() - start).total_seconds(), "seconds,")
    print("matched" if match else "did not match")


def test():
    expr = "(\*([^*]+)*\*)"
    text_l = "* is there anybody"
    text_r = " out?"
    stuff = ""
    for i in range(7):
        if i > 0:
            stuff += str(i)
        text = text_l + stuff + text_r
        print("Testing", text)
        test_match(expr, text)

test()