Log parsing regex | Python Fiddle

import re

pat = (r'(I|E|F|W)(\d{4}) (\S+)\s+(\d+) ([^:]+):(\d+)\] (.+?)'
       r'(?=(?:$|\n(?:I|E|F|W)\d{4}))')
rgx = re.compile(pat, re.DOTALL)

sample = """Log file created at: 2014/10/31 10:04:48
Running on machine: crunkleton0.sea.corp.google.com
Binary: Built on Oct 29 2014 14:48:24 (1414619304)
Binary: Built at crunkleton@crunkleton0.sea.corp.google.com:/google/src/cloud/crunkleton/fail_on_error/google3
Binary: Built for gcc-4.X.Y-crosstool-v17-hybrid-grtev3-k8
Log line format: [IWEF]mmdd hh:mm:ss.uuuuuu threadid file:line] msg
E1031 10:04:48.893985   16288 clock.cc:352] * | * | * | * | * | * | * | * | * | * | * | * | * |
E1031 10:04:48.895296   16288 clock.cc:353] * | * | * | * Initializing fake TrueTime.  Be wary!
E1031 10:04:48.895594   16288 clock.cc:354] * | * | * | * Unsafe for use with a prod universe.
E1031 10:04:48.895850   16288 clock.cc:355] * | * | * | * | * | * | * | * | * | * | * | * | * |
F1031 10:05:10.259069   18011 trace_span-impl.h:234] Check failed: internal::ValidContext(swapped_tc_) 
*** Check failure stack trace: ***
    @          0xaa3afc8  base_logging::LogMessage::SendToLog()
    @          0xaa3ba26  base_logging::LogMessage::Flush()
    @          0xaa3e195  LogMessageFatal::~LogMessageFatal()
    @          0x4a94e96  perftools::tracing::TraceSpan<>::CreateSpan()
    @          0x4a94c55  perftools::tracing::TraceSpan<>::TraceSpan()
    @          0x4a91b23  perftools::tracing::RpcClientTraceSpan::RpcClientTraceSpan()
    @          0x9477453  RPC::PrepareStart()
    @          0x9477633  RPC::InternalStart()
    @          0x94ed1af  RPC_Service::StartCall()
    @           0x91b9f3  cloud_cluster::NannyInfo::Stub::GetAllInfo()
    @           0x719b85  cloud_cluster::instance_manager::NannySensor::GetAllInfo()
    @           0x71cd0c  cloud_cluster::instance_manager::NannySensor::SendRPCIfNeeded()
    @           0x71d611  cloud_cluster::instance_manager::NannySensor::ProcessNannyTaskWithKey()
    @           0x7193ef  cloud_cluster::instance_manager::NannySensor::ProcessNannyTask()
    @           0x7210db  _MemberResultCallback_0_1<>::Run()
    @           0x7247c0  _MemberResultCallback_1_0<>::Run()
    @           0x7d8168  cloud_cluster::instance_manager::KeyedThreadPool::RunInPool()
    @           0x7d9c13  _MemberResultCallback_2_0<>::Run()
    @          0xa911a82  ThreadPoolWorker::Run()
    @          0xa9187ce  Thread::ThreadBody()
    @     0x7f3897c5014e  start_thread
F1031 10:05:10.589570   18006 trace_span-impl.h:234] Check failed: internal::ValidContext(swapped_tc_) 
*** Check failure stack trace: ***
    @          0xaa3afc8  base_logging::LogMessage::SendToLog()
    @          0xaa3ba26  base_logging::LogMessage::Flush()
    @          0xaa3e195  LogMessageFatal::~LogMessageFatal()
    @          0x4a94e96  perftools::tracing::TraceSpan<>::CreateSpan()
    @          0x4a94c55  perftools::tracing::TraceSpan<>::TraceSpan()
    @          0x4a91b23  perftools::tracing::RpcClientTraceSpan::RpcClientTraceSpan()
    @          0x9477453  RPC::PrepareStart()
    @          0x9477633  RPC::InternalStart()
    @          0x94ed1af  RPC_Service::StartCall()
    @           0x91b9f3  cloud_cluster::NannyInfo::Stub::GetAllInfo()
    @           0x719b85  cloud_cluster::instance_manager::NannySensor::GetAllInfo()
    @           0x71cd0c  cloud_cluster::instance_manager::NannySensor::SendRPCIfNeeded()
    @           0x71d611  cloud_cluster::instance_manager::NannySensor::ProcessNannyTaskWithKey()
    @           0x7193ef  cloud_cluster::instance_manager::NannySensor::ProcessNannyTask()
    @           0x7210db  _MemberResultCallback_0_1<>::Run()
    @           0x7247c0  _MemberResultCallback_1_0<>::Run()
    @           0x7d8168  cloud_cluster::instance_manager::KeyedThreadPool::RunInPool()
    @           0x7d9c13  _MemberResultCallback_2_0<>::Run()
    @          0xa911a82  ThreadPoolWorker::Run()
    @          0xa9187ce  Thread::ThreadBody()
    @     0x7f3897c5014e  start_thread
E1031 10:05:11.137338   17134 server_env_impl.cc:1144] The zonemaster told me to die, but I am already crashing, so delaying crashing due to the zonemaster's command.
E1031 10:05:11.185379   18011 process_state.cc:1432] *** SIGABRT received by PID 16288 (TID 18011) from PID 16288; stack trace: ***
E1031 10:05:11.185674   18011 process_state.cc:1433] PC: @     0x7f38978dc2b5  (unknown)  raise
    @          0xaa51e9d       1296  FailureSignalHandler()
    @     0x7f3897c58700       1744  __restore_rt
    @          0xaa3b0de        272  base_logging::LogMessage::SendToLog()
    @          0xaa3ba26        256  base_logging::LogMessage::Flush()
    @          0xaa3e195         32  LogMessageFatal::~LogMessageFatal()
    @          0x4a94e96        160  perftools::tracing::TraceSpan<>::CreateSpan()
    @          0x4a94c55        176  perftools::tracing::TraceSpan<>::TraceSpan()
    @          0x4a91b23         80  perftools::tracing::RpcClientTraceSpan::RpcClientTraceSpan()
    @          0x9477453        752  RPC::PrepareStart()
    @          0x9477633        240  RPC::InternalStart()
    @          0x94ed1af        240  RPC_Service::StartCall()
    @           0x91b9f3        160  cloud_cluster::NannyInfo::Stub::GetAllInfo()
    @           0x719b85       1360  cloud_cluster::instance_manager::NannySensor::GetAllInfo()
    @           0x71cd0c        288  cloud_cluster::instance_manager::NannySensor::SendRPCIfNeeded()
    @           0x71d611       2352  cloud_cluster::instance_manager::NannySensor::ProcessNannyTaskWithKey()
    @           0x7193ef        448  cloud_cluster::instance_manager::NannySensor::ProcessNannyTask()
    @           0x7210db        240  _MemberResultCallback_0_1<>::Run()
    @           0x7247c0        256  _MemberResultCallback_1_0<>::Run()
    @           0x7d8168         64  cloud_cluster::instance_manager::KeyedThreadPool::RunInPool()
    @           0x7d9c13         64  _MemberResultCallback_2_0<>::Run()
    @          0xa911a82        176  ThreadPoolWorker::Run()
    @          0xa9187ce        480  Thread::ThreadBody()
    @     0x7f3897c5014e  (unknown)  start_thread
F1031 10:05:23.105656   18011 trace_span-impl.h:234] Check failed: internal::ValidContext(swapped_tc_) 
*** Check failure stack trace: ***
    @          0xaa3afc8  base_logging::LogMessage::SendToLog()
    @          0xaa3ba26  base_logging::LogMessage::Flush()
    @          0xaa3e195  LogMessageFatal::~LogMessageFatal()
    @          0x4a94e96  perftools::tracing::TraceSpan<>::CreateSpan()
    @          0x4a94c55  perftools::tracing::TraceSpan<>::TraceSpan()
    @          0x4a91b23  perftools::tracing::RpcClientTraceSpan::RpcClientTraceSpan()
    @          0x9477453  RPC::PrepareStart()
    @          0x9477633  RPC::InternalStart()
    @          0x94ed1af  RPC_Service::StartCall()
    @          0x8b08c01  SvelteClient::Stub::EndSession()
    @          0x8ad341a  svw::WaiterThread::EndSession()
    @          0x8abd308  SvelteWatcher::EndSessions()
    @          0x1643d13  _FunctionResultCallback_0_0<>::Run()
    @          0xaa4f7fa  base::internal::ExecuteFailureClosures()
    @          0xaa52013  FailureSignalHandler()
    @     0x7f3897c58700  __restore_rt
    @          0xaa3b0de  base_logging::LogMessage::SendToLog()
    @          0xaa3ba26  base_logging::LogMessage::Flush()
    @          0xaa3e195  LogMessageFatal::~LogMessageFatal()
    @          0x4a94e96  perftools::tracing::TraceSpan<>::CreateSpan()
    @          0x4a94c55  perftools::tracing::TraceSpan<>::TraceSpan()
    @          0x4a91b23  perftools::tracing::RpcClientTraceSpan::RpcClientTraceSpan()
    @          0x9477453  RPC::PrepareStart()
    @          0x9477633  RPC::InternalStart()
    @          0x94ed1af  RPC_Service::StartCall()
    @           0x91b9f3  cloud_cluster::NannyInfo::Stub::GetAllInfo()
    @           0x719b85  cloud_cluster::instance_manager::NannySensor::GetAllInfo()
    @           0x71cd0c  cloud_cluster::instance_manager::NannySensor::SendRPCIfNeeded()
    @           0x71d611  cloud_cluster::instance_manager::NannySensor::ProcessNannyTaskWithKey()
    @           0x7193ef  cloud_cluster::instance_manager::NannySensor::ProcessNannyTask()
    @           0x7210db  _MemberResultCallback_0_1<>::Run()
    @           0x7247c0  _MemberResultCallback_1_0<>::Run()"""

results = rgx.findall(sample)
for result in results:
  print result

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