How can I replace a substring between page1/ and _type-A with 222.6 in the below-provided l string?

l = 'https://homepage.com/home/page1/222.6 a_type-A/go'
replace_with = '222.6'

Expected result:

https://homepage.com/home/page1/222.6_type-A/go

I tried:

import re
re.sub('page1/.*?_type-A','',l, flags=re.DOTALL)

But it also removes page1/ and _type-A.

CodePudding user response：

You can use

import re
l = 'https://' 'homepage.com/home/page1/222.6 a_type-A/go'
replace_with = '222.6'
print (re.sub('(page1/).*?(_type-A)',fr'\g<1>{replace_with}\2',l, flags=re.DOTALL))

Output: https://homepage.com/home/page1/222.6_type-A/go

See the Python demo online

Note you used an empty string as the replacement argument. In the above snippet, the parts before and after .*? are captured and \g<1> refers to the first group value, and \2 refers to the second group value from the replacement pattern. The unambiguous backreference form (\g<X>) is used to avoid backreference issues since there is a digit right after the backreference.

Since the replacement pattern contains no backslashes, there is no need preprocessing (escaping) anything in it.

CodePudding user response：

You may use re.sub like this:

import re

l = 'https://homepage.com/home/page1/222.6 a_type-A/go'
replace_with = '222.6'

print (re.sub(r'(?<=page1/).*?(?=_type-A)', replace_with, l))

Output:

https://homepage.com/home/page1/222.6_type-A/go

RegEx Demo

RegEx Breakup:

• (?<=page1/): Lookbehind to assert that we have page1/ at previous position
• .*?: Match 0 or more of any string (lazy)
• (?=_type-A): Lookahead to assert that we have _type-A at next position

CodePudding user response：

This works:

import re

l = 'https://homepage.com/home/page1/222.6 a_type-A/go'
pattern = r"(?<=page1/).*?(?=_type)"
replace_with = '222.6'

s = re.sub(pattern, replace_with, l)
print(s)

The pattern uses the positive lookahead and lookback assertions, ?<= and ?=. A match only occurs if a string is preceded and followed by the assertions in the pattern, but does not consume them. Meaning that re.sub looks for a string with page1/ in front and _type behind it, but only replaces the part in between.