REGEX检查前25个字符内的短语

Question

I'm using regular expressions to match a keyword. Is it possible to check for this keyword within ONLY the first 25 characters?

For example, I want to find "APPLE" :

'Johnny picked an APPLE from the tree' - Match Found (within first 25 chars)

'Johnny picked something from a tree that had an APPLE' - Not Found (because APPLE does not exist within the first 25 chars).

Is there syntax for this?

Answer 1

A simple solution would be to slice off the 25 first characters and then do the regex matching.

myString = 'Johnny picked an APPLE from the tree'
slicedString = myString[:25]
# do regex matching on slicedString

Answer 2

Yes it is. You prefix your keyword with zero to 25 - length(keyword) "any" characters.

I'm not sure if this is actual python syntax, but the RE should be ^.{0,20}APPLE .

Edit: for clarification

• ^.{0,20}APPLE should be used when looking for a substring. Use this in Python.
• .{0,20}APPLE.* should be used when matching the whole string.

Another edit: Apparently Python only has substring mode, so the ^ anchor is necessary.

Answer 3

Try using a slice on your string:

>>> import re
>>> string1 = "Johnny picked an APPLE from the tree"
>>> string2 = "Johnny picked something from a tree that had an APPLE"
>>> re.match(".*APPLE.*", string1[:25])  # Match
<_sre.SRE_Match object at 0x2364030>
>>> re.match(".*APPLE.*", string2[:25])  # Does not match