python-patterns/command.py at master · Problematic/python-patterns

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import os

class MoveFileCommand(object):

def __init__(self, src, dest):

self.src = src

self.dest = dest

def execute(self):

self()

def __call__(self):

print('renaming {} to {}'.format(self.src, self.dest))

os.rename(self.src, self.dest)

def undo(self):

print('renaming {} to {}'.format(self.dest, self.src))

os.rename(self.dest, self.src)

if __name__ == "__main__":

undo_stack = []

ren1 = MoveFileCommand('foo.txt', 'bar.txt')

ren2 = MoveFileCommand('bar.txt', 'baz.txt')

# commands are just pushed into the command stack

for cmd in ren1, ren2:

undo_stack.append(cmd)

# they can be executed later on will

for cmd in undo_stack:

cmd.execute() # foo.txt is now renamed to baz.txt

# and can also be undone on will

for cmd in undo_stack:

undo_stack.pop().undo() # Now it's bar.txt

undo_stack.pop().undo() # and back to foo.txt