Add "reinstall()" method to make it easier in spawn multiprocessing

loguru/_logger.py

@@ -86,6 +86,7 @@
 import contextlib
 import functools
 import logging
+import os
 import re
 import sys
 import warnings
@@ -230,6 +231,7 @@ class Logger:
     def __init__(self, core, exception, depth, record, lazy, colors, raw, capture, patchers, extra):
         self._core = core
         self._options = (exception, depth, record, lazy, colors, raw, capture, patchers, extra)
+        self._own_pid = os.getpid()
 
     def __repr__(self):
         return "<loguru.logger handlers=%r>" % list(self._core.handlers.values())
@@ -1752,6 +1754,46 @@ def configure(self, *, handlers=None, levels=None, extra=None, patcher=None, act
 
         return [self.add(**params) for params in handlers]
 
+    def _replace_core(self, core: Core):
+        self._core = core
+
+    def reinstall(self):
+        """Reinstall the core of logger.
+
+        When using multiprocessing, you can pass logger as a parameter to the target of
+        ``multiprocessing.Process``, and run this method once, thus you don't need to pass logger to every
+        function you called in the same process with spawn multiprocessing.
+
+        Examples
+        --------
+        >>> def subworker(logger_):
+        ...     logger_.reinstall()
+        ...     logger.info("Child")
+        ...     deeper_subworker()
+
+        >>> def deeper_subworker():
+        ...     logger.info("Grandchild")
+
+        >>> def test_process_spawn():
+        ...     spawn_context = multiprocessing.get_context("spawn")
+        ...     logger.add("file.log", context=spawn_context, enqueue=True, catch=False)
+        ...
+        ...     process = spawn_context.Process(target=subworker, args=(logger,))
+        ...     process.start()
+        ...     process.join()
+
+        ...     assert process.exitcode == 0
+
+        ...     logger.info("Main")
+        ...     logger.remove()
+        """
+        if self._own_pid == os.getpid():  # same process
+            return
+        from loguru import logger
+
+        logger._replace_core(self._core)
+
+
     def _change_activation(self, name, status):
         if not (name is None or isinstance(name, str)):
             raise TypeError(

tests/test_multiprocessing.py

@@ -36,6 +36,16 @@ def subworker(logger_):
     logger_.info("Child")
 
 
+def subworker_spawn(logger_):
+    logger_.reinstall()
+    logger.info("Child")
+    deeper_subworker()
+
+
+def deeper_subworker():
+    logger.info("Grandchild")
+
+
 def subworker_inheritance():
     logger.info("Child")
 
@@ -209,7 +219,7 @@ def test_process_spawn(spawn_context):
 
     logger.add(writer, context=spawn_context, format="{message}", enqueue=True, catch=False)
 
-    process = spawn_context.Process(target=subworker, args=(logger,))
+    process = spawn_context.Process(target=subworker_spawn, args=(logger,))
     process.start()
     process.join()
 
@@ -218,7 +228,7 @@ def test_process_spawn(spawn_context):
     logger.info("Main")
     logger.remove()
 
-    assert writer.read() == "Child\nMain\n"
+    assert writer.read() == "Child\nGrandchild\nMain\n"
 
 
 @pytest.mark.skipif(os.name == "nt", reason="Windows does not support forking")