ブロック内のコードをスキップできる + スコープを共有しない with statetment

gistfile1.py

# 1. ブロック内のコードを実行しない with　-------
# refs http://stackoverflow.com/questions/12594148/skipping-execution-of-with-block

import sys
import inspect

class SkipContext:
    def __enter__(self):
        # 1. SkipContextの外側のframeを取得
        self.frame, _, _, _, _, _ = inspect.getouterframes(inspect.currentframe())[1]
        self.frame.f_trace = self.trace
        sys.settrace(lambda *args, **keys: None) # 2. settraceを有効にする

    def trace(self, frame, event, arg):
        raise Exception('Skip with block') # 4. 3の行が実行される前にフックされて raiseされる

    def __exit__(self, exec_type, exec_value, traceback):
        # 5. 3の行は実行されずに、__exit__ にたどり着いて強制的にwithが終了
        sys.settrace(None)
        return True

with SkipContext():
    print('Not execute this line.') # 3. この行が実行されようとする

# 2. スコープを共有しない with ------------

import inspect
import copy

class IsolatedScopeContext:
    def __enter__(self):
        self.frame, _, _, _, _, _ = inspect.getouterframes(inspect.currentframe())[1]
        self.orig_globals = copy.copy(self.frame.f_globals) # 1. with に入る前の globalsを保存

    def __exit__(self, exec_type, exec_value, traceback):
        # 2. with を抜ける時に1で保存した globalsを復活
        for k in list(self.frame.f_globals.keys()):
            self.frame.f_globals.pop(k, None)
        for k, v in self.orig_globals.items():
            self.frame.f_globals[k] = v
        return True

spam = 'spam'

with IsolatedScopeContext(): # withの抜けたあとに、この時点でのglobalsを復元する
    spam = 'egg'

with IsolatedScopeContext():
    print(spam) # => 'spam'


# 3 1 と 2を mix したやつ ------------------

import inspect
import sys
import copy

class SkipException(Exception):
    pass

class SkippableContext:

    def __init__(self, skip=False, isolated_scope=False):
        self.skip = skip
        self.isolated_scope = isolated_scope

    def __enter__(self):
        self.frame, _, _, _, _, _ = inspect.getouterframes(inspect.currentframe())[1]
        if self.skip:
            self.frame.f_trace = self.trace
            sys.settrace(lambda *args, **keys: None)
        if self.isolated_scope:
            self.orig_globals = copy.copy(self.frame.f_globals)

    def trace(self, frame, event, arg):
        raise SkipException('Skip this context.')

    def restore_globals(self):
        for k in list(self.frame.f_globals.keys()):
            self.frame.f_globals.pop(k, None)
        for k, v in self.orig_globals.items():
            self.frame.f_globals[k] = v

    def __exit__(self, exec_type, exec_value, traceback):
        sys.settrace(None)
        if self.isolated_scope:
            self.restore_globals()
        if exec_type is SkipException:
            return True

with SkippableContext():
    print('Execute this line.')

with SkippableContext(skip=True):
    print('Not Execute this line.')


var1 = 'var1'
with SkippableContext(isolated_scope=True):
    var1 = 'update1'
    print(var1)

with SkippableContext(isolated_scope=True):
    print(var1)
    var1 = 'update2'

print(var1) # => 'var1'