import re
sample="""[2019-01-02 16:15:17.882][P:1624/T:1420][UIPCall.cpp:743 
CUIPCall::HandleUICEvent()][Enter]
[2019-01-02 16:15:17.883][P:1624/T:1420][UIPCallState.cpp:1776 
CUIPCallIncomingLine1State::HandleUICEvent()][Enter]"""
pattern=r'\[(.*?)\]\[(.*?)\]\[(.+?)(HandleUICEvent|FastNtfClosed_Line1_Common|Login|Logout)\(\)\]\[(.*?)\]$'
 
p = re.compile(pattern, re.MULTILINE | re.DOTALL)
 
print([(x.start(), x.end()) for x in p.finditer(sample)])

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