Regex matching complex string

Question

I have following exemplary strings:

- FCF_VD_ID,
- [FCF_VD_Alert_L1, ..., FCF_VD_Alert_L8],
- FCF_VD_SyncID,
- [FCF_VRU_Alert_FCV, FCF_VRU_Alert_A ..., FCF_VRU_Alert_H],
- [COM_Cam_Frame_1, ..., COM_Cam_Frame_8]

And I need to extract some specific parts from these strings. Specifically I need the core name of each string which in the above cases is everything till enumerator. As an enumerator I treat L1->L8, FCV, A->H, 1->8.

As output I need to get two strings:

core, enum = re.match(regex, string)

Example:

FCF_Alert_L1 -> FCF_Alert, L1
FCF_SyncID -> FCF_Sync_ID, None
FCF_VRU_Alert_FCV -> FCF_VRU_Alert, FCV

Unfortunately my regex ^([A-Za-z_]+(ID)?)([A-Z]+\d+|[A-Z]+|\d+)?$ does not work. Can anybody point out the problem in this regex? For FCF_VD_ID_L1 I receive ('FCF_VD_ID_L', None, '1') which is completely not what I require.

Maybe you just want re.findall(r'(\w+)_(\w+)', text)? Or, (\w+)_(L?\d+|FCV|[AH]|[A-Za-z]*ID)\b? See this regex demo. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented May 7, 2021 at 14:32
Perhaps like this ^([^_\n]+(?:_[^_\n]+)*?)(?:_(L[1-8]|FCV|[A-Z]|[1-8]|ID))?$ regex101.com/r/4QnKNy/1 — The fourth bird
– The fourth bird, Commented May 7, 2021 at 14:54

Nick · Accepted Answer · 2021-05-07 15:28:27Z

1

It looks like you're looking for this regex:

(\w+?)(?:_(L[1-8]|FCV|[A-H])|([1-8]))?$

which matches a minimal number of word characters (\w+?) followed by an enum part of _ and L1-L8, FCV or A-H, or a digit in the range 1-8.

Note since you are using re.match no ^ is required at the beginning since re.match anchors all matches to the start of the string.

In python:

import re

strs = [
  'FCF_VD_ID', 'FCF_VD_Alert_L1', 'FCF_VD_Alert_L8',
  'FCF_VD_SyncID', 'FCF_VRU_Alert_FCV', 'FCF_VRU_Alert_A',
  'FCF_VRU_Alert_H', 'COM_Cam_Frame_1', 'COM_Cam_Frame_8',
  'idObject1'
]

regex = '(\w+?)(?:_(L[1-8]|FCV|[A-H])|([1-8]))?$'

for s in strs:
    core, enum1, enum2 = re.match(regex, s).groups()
    enum = enum1 if enum1 else enum2
    print(s + ' => ', (core, enum))

Output:

FCF_VD_ID =>  ('FCF_VD_ID', None)
FCF_VD_Alert_L1 =>  ('FCF_VD_Alert', 'L1')
FCF_VD_Alert_L8 =>  ('FCF_VD_Alert', 'L8')
FCF_VD_SyncID =>  ('FCF_VD_SyncID', None)
FCF_VRU_Alert_FCV =>  ('FCF_VRU_Alert', 'FCV')
FCF_VRU_Alert_A =>  ('FCF_VRU_Alert', 'A')
FCF_VRU_Alert_H =>  ('FCF_VRU_Alert', 'H')
COM_Cam_Frame_1 =>  ('COM_Cam_Frame', '1')
COM_Cam_Frame_8 =>  ('COM_Cam_Frame', '8')
idObject1 =>  ('idObject', '1')

edited May 7, 2021 at 15:28

answered May 7, 2021 at 14:57

Nick

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9 Comments

Filip Szczybura Over a year ago

That's probably very close to what I am searching for. But specifically I aim for that last enum which can start with '_' or not. If we have something like idObject1 I want that 1 to be the enum. The input in the post's description is just an example.

Nick Over a year ago

@FilipSzczybura this is why it's really important to include all forms of sample data in your question. Your problem though is what about something like abcID; is that (abcID, None) or (abcI, D)?

Filip Szczybura Over a year ago

'All' means thousands. '(\w+?)(?:_?(\\d+|[A-Z]+\\d+|[A-Z]+))?$' is closest what I am searching for, but I want to exclude 'ID|Id|id' from enum extraction. So for COM_Cam_Sync_ID I don't want do get the enum

Nick Over a year ago

Do any of the enums have to have _ before them? or is it optional for all of them? If it is, I don't see how you can tell whether ABC should be (ABC, None) or (AB, C) (since C is a valid enum)

Filip Szczybura Over a year ago

Most of these enums will have leading _. The exception is a single digit enum like idObject1. Here the enum is 1. Otherwise I want to get any enum that is: _[A-Z]+\\d+ or _[A-Z]+ or without _ just \\d+. You can notice that enums after _ always are uppercase

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