Python snippet for monitoring where files were opened

filemonitor.py

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from __future__ import print_function
import traceback
import atexit
import textwrap
import io

try:
    import __builtin__ as builtins
except ImportError:
    import builtins

class FileMonitor(object):
    """
    Collect stacktraces of where files are opened, and prints them out before the
    program exits.

    - Has partial support for python3 

    Example
    -------

    # BEGIN monitor.py
    from filemonitor import FileMonitor
    FileMonitor().patch()
    f = open('/bin/ls')
    # END monitor.py

    $ python monitor.py
      ----------------------------------------------------------------------------
      path = /bin/ls
      >   File "monitor.py", line 3, in <module>
      >     f = open('/bin/ls')
      ----------------------------------------------------------------------------

    Acknowledgements
    ----------------
    http://stackoverflow.com/questions/2023608/check-what-files-are-open-in-python
    Solution modified from http://stackoverflow.com/a/2023709. Authored by Claudiu
    """
    def __init__(self, print_only_open=True):
        self.openfiles = []
        self.oldopen = builtins.open

        self.oldfile = getattr(builtins, 'file', io.FileIO)

        self.do_print_only_open = print_only_open
        self.in_use = False

        class File(self.oldfile):

            def __init__(this, *args, **kwargs):
                path = args[0]

                self.oldfile.__init__(this, *args, **kwargs)
                if self.in_use:
                    return
                self.in_use = True
                self.openfiles.append((this, path, this._stack_trace()))
                self.in_use = False

            def close(this):
                self.oldfile.close(this)

            def _stack_trace(this):
                try:
                    raise RuntimeError()
                except RuntimeError as e:
                    stack = traceback.extract_stack()[:-2]
                    return traceback.format_list(stack)

        self.File = File

    def patch(self):
        builtins.open = self.File

        try:
            builtins.file = self.File
        except AttributeError:
            pass

        atexit.register(self.exit_handler)

    def unpatch(self):
        builtins.open = self.oldopen
        try:
            builtins.file = self.oldfile
        except AttributeError:
            pass

    def exit_handler(self):
        indent = '  > '
        terminal_width = 80
        for file, path, trace in self.openfiles:
            if file.closed and self.do_print_only_open:
                continue
            print("-" * terminal_width)
            print("  {} = {}".format('path', path))
            lines = ''.join(trace).splitlines()
            _updated_lines = []
            for l in lines:
                ul = textwrap.fill(l,
                                   initial_indent=indent,
                                   subsequent_indent=indent,
                                   width=terminal_width)
                _updated_lines.append(ul)
            lines = _updated_lines
            print('\n'.join(lines))
            print("-" * terminal_width)
            print()

if __name__ == '__main__':
    FileMonitor().patch()
    open('/bin/ls')

thanks - reading...