re.error: nothing to repeat at position 0

[mennatallah644]

I am facing this issue when i am trying to loop on certain expressions to find their occurences in string

I am using the last version of the package

here is the code

matches = re.finditer(r"\b{}\b".format(substring), string)
OFFSETS = [(_.start(), _.end()) for _ in matches ]

the error occurs in the line where i use finditer
it says
re.error: nothing to repeat at position 0

[mrabarnett]

The .format is just building a string that will be used as a pattern. If the resulting string is not a valid pattern, then the module will complain when it tries to compile it.

Whatever you have in substring is not a valid pattern.

[mennatallah644]

@mrabarnett
actually I was passing the substring pattern which is starting with * but i didn't mean to use it as regex character and after i used the re.escape()

matches = re.finditer(r"\b{}\b".format(re.escape(substring)), string)
OFFSETS = [(_.start(), _.end()) for _ in matches ]

the error gone but no matching came even the substring already exists in the string
ex:
substring = '*Hello'
String = "*Hello world"

why no matching came even the substring exists in the string ?

[mrabarnett]

The pattern you're building is \b\*Hello, which will match a word boundary, then a *, then Hello. The string you have starts with a *, followed by Hello. There's no word boundary before the *.