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 python_37

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_utils.py

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import os

import sys

from typing import Any, Dict

# Avoid "LookupError: unknown encoding: ascii" when open() called in a destructor

outnull_file = open(os.devnull, "w")

errnull_file = open(os.devnull, "w")

STDOUT_FILENO = 1

STDERR_FILENO = 2

class suppress_stdout_stderr(object):

# NOTE: these must be "saved" here to avoid exceptions when using

# this context manager inside of a __del__ method

sys = sys

os = os

def __init__(self, disable: bool = True):

self.disable = disable

# Oddly enough this works better than the contextlib version

def __enter__(self):

if self.disable:

return self

self.old_stdout_fileno_undup = STDOUT_FILENO

self.old_stderr_fileno_undup = STDERR_FILENO

self.old_stdout_fileno = self.os.dup(self.old_stdout_fileno_undup)

self.old_stderr_fileno = self.os.dup(self.old_stderr_fileno_undup)

self.old_stdout = self.sys.stdout

self.old_stderr = self.sys.stderr

self.os.dup2(outnull_file.fileno(), self.old_stdout_fileno_undup)

self.os.dup2(errnull_file.fileno(), self.old_stderr_fileno_undup)

self.sys.stdout = outnull_file

self.sys.stderr = errnull_file

return self

def __exit__(self, *_):

if self.disable:

return

# Check if sys.stdout and sys.stderr have fileno method

self.sys.stdout = self.old_stdout

self.sys.stderr = self.old_stderr

self.os.dup2(self.old_stdout_fileno, self.old_stdout_fileno_undup)

self.os.dup2(self.old_stderr_fileno, self.old_stderr_fileno_undup)

self.os.close(self.old_stdout_fileno)

self.os.close(self.old_stderr_fileno)

class MetaSingleton(type):

"""

Metaclass for implementing the Singleton pattern.

"""

_instances: Dict[type, Any] = {}

def __call__(cls, *args: Any, **kwargs: Any) -> Any:

if cls not in cls._instances:

cls._instances[cls] = super(MetaSingleton, cls).__call__(*args, **kwargs)

return cls._instances[cls]

class Singleton(object, metaclass=MetaSingleton):

"""

Base class for implementing the Singleton pattern.

"""

def __init__(self):

super(Singleton, self).__init__()