method_logger.py

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# SPDX-License-Identifier: LGPL-3.0-or-later
# SPDX-FileCopyrightText: Copyright CERN for the benefit of the SHiP Collaboration
 
import sys
from functools import wraps
 
 
class MethodLogger:
    """
    This class wraps a instance of an arbitrary class, intercepts all its
    method calls and logs them to a file (default: `sys.stdout`).
 
    >>> import method_logger as ml
    >>> from StringIO import StringIO
    >>> class TestClass(object):
    ...     def __init__(self):
    ...         pass
    ...     def func(*args, **kwargs):
    ...         pass
    ...
    >>> cl = TestClass()
    >>> sink = StringIO()
    >>> lg = ml.MethodLogger(cl, sink=sink)
    >>> lg.func(3, y=8, foo='bar')
    >>> sink.getvalue()
    "TestClass.func(3, y=8, foo='bar')\\n"
    >>> sink.close()
    """
 
    def __init__(self, wrapped_instance, sink=sys.stdout) -> None:
        self._class = wrapped_instance
        self._sink = sink
        self._prefix = type(wrapped_instance).__name__ + "."
 
    def method_logger(self, met):
        qualified_name = self._prefix + str(met.__name__)
 
        @wraps(met)
        def _logger(*args, **kwargs):
            args_str = ", ".join(repr(arg) for arg in args)
            kwargs_str = ", ".join(str(k) + "=" + repr(v) for (k, v) in kwargs.items())
            all_args_str = args_str + (", " if len(kwargs_str) > 0 else "") + kwargs_str
            print(f"{qualified_name}({all_args_str})", file=self._sink)
            return met.__call__(*args, **kwargs)
 
        return _logger
 
    def __getattr__(self, attr):
        return self.method_logger(getattr(self._class, attr))