I want to implement a Stack in Python3 and for some methods which need to check Stack Empty or Stack Full, I want to write decorators which would take care of checking the same and be usable for various methods which need those checks.
This is what I have tried to do (Please check the implementation of push and pop methods):
repl.it link : https://repl.it/@Ishitva/Stack
class StackFullException(Exception):
pass
class StackEmptyException(Exception):
pass
def checkStackFull(instance):
def check(func):
def execute(*args, **kwargs):
if len(instance.items) <= instance.limit:
return func(*args, **kwargs)
raise StackFullException
return execute
return check
def checkStackEmpty(instance):
def check(func):
def execute(*args, **kwargs):
if len(instance.items) > -1:
return func(*args, **kwargs)
raise StackEmptyException
return execute
return check
class Stack():
def __init__(self, limit=10):
self.items = []
self.limit = limit
@checkStackFull(self)
def push(item):
self.items.append(item)
return item
@checkStackEmpty(self)
def pop():
return self.items.pop()
def getSize():
return len(self.items)
This gives me the following exception:
Traceback (most recent call last):
File "main.py", line 28, in <module>
class Stack():
File "main.py", line 34, in Stack
@checkStackFull(self)
NameError: name 'self' is not defined
But if you really need to do that, then code:
class StackFullException(Exception):
pass
class StackEmptyException(Exception):
pass
def checkStackFull(func):
def execute(self, *args, **kwargs):
if len(self.items) <= self.limit:
return func(self, *args, **kwargs)
raise StackFullException()
return execute
def checkStackEmpty(func):
def execute(self, *args, **kwargs):
if len(self.items):
return func(self, *args, **kwargs)
raise StackEmptyException()
return execute
class Stack():
def __init__(self, limit=10):
self.items = []
self.limit = limit
@checkStackFull
def push(self, item):
self.items.append(item)
return item
@checkStackEmpty
def pop(self):
return self.items.pop()
def getSize(self):
return len(self.items)
And by the way pop from empty list will raise IndexError anyway so you could just use that.