python-patterns/behavioral/command.py at master · paveu/python-patterns · GitHub

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ importprint_function
importos
fromos.pathimportlexists


classMoveFileCommand(object):

def__init__(self, src, dest):
self.src=src
self.dest=dest

defexecute(self):
self.rename(self.src, self.dest)

defundo(self):
self.rename(self.dest, self.src)

defrename(self, src, dest):
print(u"renaming %s to %s"% (src, dest))
os.rename(src, dest)


defmain():
command_stack= []

# commands are just pushed into the command stack
command_stack.append(MoveFileCommand('foo.txt', 'bar.txt'))
command_stack.append(MoveFileCommand('bar.txt', 'baz.txt'))

# verify that none of the target files exist
assert(notlexists("foo.txt"))
assert(notlexists("bar.txt"))
assert(notlexists("baz.txt"))
try:
withopen("foo.txt", "w"): # Creating the file
pass

# they can be executed later on
forcmdincommand_stack:
cmd.execute()

# and can also be undone at will
forcmdinreversed(command_stack):
cmd.undo()
finally:
os.unlink("foo.txt")

if__name__=="__main__":
main()

### OUTPUT ###
# renaming foo.txt to bar.txt
# renaming bar.txt to baz.txt
# renaming baz.txt to bar.txt
# renaming bar.txt to foo.txt