Home/ Questions/Q 6566317
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-25T14:12:09+00:00

s/(?P<head>\[\[foo[^\[]*)abc/\g<head>def s/(?=\[\[foo[^\[]*)abc/def Which is more efficient? Are there any other ways to make it

  • 0
s/(?P<head>\[\[foo[^\[]*)abc/\g<head>def


s/(?=\[\[foo[^\[]*)abc/def

Which is more efficient? Are there any other ways to make it more efficient? Please note that although I used Perl-style syntax for illustration purposes, I’m actually using Python’s re library, which doesn’t allow the \K (keep) keyword.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    (?P<head>\[\[foo[^\[]*)abc in python using the re module is way faster:

    import time
import re

rec1 = re.compile('(?P<head>\[\[foo[^\[]*)abc')
rec2 = re.compile('(?=\[\[foo[^\[]*)abc')

total1, total2 = 0.0, 0.0

def timeRE(ver):
    x = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_1234567890_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" * 100)
    t1 = time.time()
    if ver is 1:
        rec1.sub("def", x)
    else:
        rec2.sub("def", x)
    return (time.time() - t1)

for x in xrange(50000):
    total1 += timeRE(1)

for x in xrange(50000):
    total2 += timeRE(2)

print total1
print total2

    Outputs:

    4.27380466461
16.9591507912

    Edit (Run a few more times doing both calls in the same loop):

    for x in xrange(50000):
    total1 += timeRE(1)
    total2 += timeRE(2)

    Outputs:

    4.26199269295
17.2384319305

    Edit (Fixing sub to match question):

    import time
import re
rec1 = re.compile('(?P<head>\[\[foo[^\[]*)abc')
rec2 = re.compile('(?=\[\[foo[^\[]*)abc')
total1, total2 = 0.0, 0.0
def timeRE(ver):
    x = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_1234567890_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" * 100)
    t1 = time.time()
    if ver is 1:
        rec1.sub("\g<head>def", x)
    else:
        rec2.sub("def", x)
    return (time.time() - t1)

for x in xrange(50000):
    total1 += timeRE(1)
    total2 += timeRE(2)
print total1
print total2

    Outputs: 

    Run 1:
4.62282061577
17.8212277889

Run 2:    
4.6660721302
17.1630160809

Run 3:
4.62124109268
17.21393013

    Edit (with a string that will match the REGEX):

    import time
import re

rec1 = re.compile('(?P<head>\[\[foo[^\[]*)abc')
rec2 = re.compile('(?=\[\[foo[^\[]*)abc')
total1, total2 = 0.0, 0.0

def timeRE(ver):
    x = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_1234567890_<head>_<tail>_</head>_</tail>_abcdefghijklmnopqrstuvwxyz_<head>[[fooBAR_ABCDEFGHIJKLMNOPQRSTUVWXYZ_abc]]]]defghiojklmnopqrstuvwyz" * 100)
    t1 = time.time()
    if ver is 1:
        rec1.sub("\g<head>def", x)
    else:
        rec2.sub("def", x)
    return (time.time() - t1)

for x in xrange(50000):
    total1 += timeRE(1)
    total2 += timeRE(2)

print total1
print total2

    Output:

    23.4271130562
29.6934807301

    And one final run:

    import time
import re
rec1 = re.compile('(?P<head>\[\[foo[^\[]*)abc')
rec2 = re.compile('(?=\[\[foo[^\[]*)abc')
total1, total2 = 0.0, 0.0
def timeRE(ver):
    x = ("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_1234567890_<head>_<tail>_</head>_</tail>_abcdefghijklmnopqrstuvwxyz_<head>[[fooBAR_ABCDEFGHIJKLMNOPQRSTUVWXYZ_abc]]]]defghiojklmnopqrstuvwyz" * 100)
    t1 = time.time()
    if ver is 1:
        rec1.sub("\g<head>def", x)
    else:
        rec2.sub("def", x)
    return (time.time() - t1)
for x in xrange(50000):
    total1 += timeRE(1)
    total2 += timeRE(2)
print "Method 1: Avg run took: %+0.7f - With a total of: %+0.7f" % ((total1 / 50000.0), total1)
print "Method 2: Avg run took: %+0.7f - With a total of: %+0.7f" % ((total2 / 50000.0), total2)

    Output:

    Method 1: Avg run took: +0.0004924 - With a total of: +24.6196477
Method 2: Avg run took: +0.0005921 - With a total of: +29.6053855
    • 0