use same logger throughout zarr-python

Author: K-Meech

src/zarr/__init__.py

@@ -1,3 +1,7 @@
+import functools
+import logging
+from typing import Literal
+
 from zarr._version import version as __version__
 from zarr.api.synchronous import (
     array,
@@ -37,6 +41,8 @@
 # in case setuptools scm screw up and find version to be 0.0.0
 assert not __version__.startswith("0.0.0")
 
+_logger = logging.getLogger(__name__)
+
 
 def print_debug_info() -> None:
     """
@@ -85,6 +91,58 @@ def print_packages(packages: list[str]) -> None:
     print_packages(optional)
 
 
+# The decorator ensures this always returns the same handler (and it is only
+# attached once).
+@functools.cache
+def _ensure_handler() -> logging.Handler:
+    """
+    The first time this function is called, attach a `StreamHandler` using the
+    same format as `logging.basicConfig` to the Zarr-Python root logger.
+
+    Return this handler every time this function is called.
+    """
+    handler = logging.StreamHandler()
+    handler.setFormatter(logging.Formatter(logging.BASIC_FORMAT))
+    _logger.addHandler(handler)
+    return handler
+
+
+def set_log_level(
+    level: Literal["NOTSET", "DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"],
+) -> None:
+    """Set the logging level for Zarr-Python.
+
+    Zarr-Python uses the standard library `logging` framework under the root
+    logger 'zarr'.  This is a helper function to:
+
+    - set Zarr-Python's root logger level
+    - set the root logger handler's level, creating the handler
+      if it does not exist yet
+
+    Parameters
+    ----------
+    level : str
+        The logging level to set.
+    """
+    _logger.setLevel(level)
+    _ensure_handler().setLevel(level)
+
+
+def set_format(log_format: str) -> None:
+    """Set the format of logging messages from Zarr-Python.
+
+    Zarr-Python uses the standard library `logging` framework under the root
+    logger 'zarr'. This sets the format of log messages from the root logger's StreamHandler.
+
+    Parameters
+    ----------
+    log_format : str
+        A string determining the log format (as defined in the standard library's `logging` module
+        for logging.Formatter)
+    """
+    _ensure_handler().setFormatter(logging.Formatter(fmt=log_format))
+
+
 __all__ = [
     "Array",
     "AsyncArray",

src/zarr/_cli/cli.py

@@ -4,6 +4,7 @@
 
 import typer
 
+import zarr
 import zarr.metadata.migrate_v3 as migrate_metadata
 from zarr.core.sync import sync
 from zarr.storage._common import make_store
@@ -13,17 +14,13 @@
 logger = logging.getLogger(__name__)
 
 
-def _set_logging_config(*, verbose: bool) -> None:
+def _set_logging_level(*, verbose: bool) -> None:
     if verbose:
-        lvl = logging.INFO
+        lvl = "INFO"
     else:
-        lvl = logging.WARNING
-    fmt = "%(message)s"
-    logging.basicConfig(level=lvl, format=fmt)
-
-
-def _set_verbose_level() -> None:
-    logging.getLogger().setLevel(logging.INFO)
+        lvl = "WARNING"
+    zarr.set_log_level(cast(Literal["INFO", "WARNING"], lvl))
+    zarr.set_format("%(message)s")
 
 
 class ZarrFormat(str, Enum):
@@ -96,7 +93,7 @@ def migrate(
     (every group / array). v2 files (.zarray, .zattrs etc.) will be left as-is.
     """
     if dry_run:
-        _set_verbose_level()
+        _set_logging_level(verbose=True)
         logger.info(
             "Dry run enabled - no new files will be created or changed. Log of files that would be created on a real run:"
         )
@@ -154,7 +151,7 @@ def remove_metadata(
     Note - this will remove metadata files at all levels of the hierarchy (every group and array).
     """
     if dry_run:
-        _set_verbose_level()
+        _set_logging_level(verbose=True)
         logger.info(
             "Dry run enabled - no files will be deleted or changed. Log of files that would be deleted on a real run:"
         )
@@ -182,7 +179,7 @@ def main(
     """
     See available commands below - access help for individual commands with zarr COMMAND --help.
     """
-    _set_logging_config(verbose=verbose)
+    _set_logging_level(verbose=verbose)
 
 
 if __name__ == "__main__":