Storing value with limits in object
I'm trying to limit a value stored by object (either int or float): class Limited(object): def __init__(self, value, min, max): self.min, self.max = min, max self.n = value def set_n(self,value): if value < self.min: # boundary check self.n = self.min if value > self.max: self.n = self.max else: self.n = value n = property(lambda self : self._value, set_n) This works, except I would like the class to behave like built-in types, so I can use it like this: a = Limited(7, 0, 10) b = math.sin(a) So that object itself returns it's value (which is stored in a.n). Is this possible? -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing value with limits in object
> Not with normal vars, because = is a rebinding operator in Python, > rather than assignment. > > You can do (close to) the above with object properties. > > David. Yes, but it's done with built-in types like int and float. I suspect I could subclass from them and implement limits, but I would have to make seperate class for each type. Can I override conversion methods like int() and float() within my class? -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing value with limits in object
> In theory you could hack Python's internal locals or globals > dictionary so that it did something unusual while looking up your > object. But in practice this doesn't work, because the returned > objects (when you call globals() or locals()) attributes are readonly. > Probably because those internal lookup dicts are implemented in > optimized C not Python, and the C implementation doesn't let you > redefine it's internals via the Python interface. > > David. I'll settle for implementing the __call__() method to return the value as I have no intention to mess around with Python's internal mechanisms. Thanks a lot for your deep insight. -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing value with limits in object
> Why not make it a function? > > function assignLimited(value, vmin, vmax): > value = max(vmin, value) > value = min(vmax, value) > return value > > > a = assignLimited(7, 0, 10) > > > Seems like it solves your problem relatively cleanly. > Note: I also removed min/max variables because they would mask the > built-in min/max functions. > > -Larry Yes, the simple solution is often the best. Still, I'm going for object oriented solution because I want the value and it's limits to be kept together as I'll have many such values with different limits. Storing all the limits in caller namespace is not really an option. -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing value with limits in object
> Why not make it a function? > > function assignLimited(value, vmin, vmax): > value = max(vmin, value) > value = min(vmax, value) > return value > > > a = assignLimited(7, 0, 10) > > > Seems like it solves your problem relatively cleanly. > Note: I also removed min/max variables because they would mask the > built-in min/max functions. > > -Larry Yes, the simple solution is often the best. Still, I'm going for object oriented solution because I want the value and it's limits to be kept together as I'll have many such values with different limits. Storing all the limits in caller namespace is not really an option. -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing value with limits in object
> I bet you didn't even try this, unless your definition of "works" > includes a "RuntimeError: maximum recursion depth exceeded". Here's a > a working version: Actually, the version I'm using is somewhat bigger. I removed docstrings and recklessly stripped away some methods to make it shorter concise and incorrect. > For (most) math.* functions it suffices to define __float__, so the > above works. For making it behave (almost) like a regular number, > you'd have to write many more special methods: > http://docs.python.org/ref/numeric-types.html. > Here's a possible start: > (...) Yes, this is very close to what I was looking for. It implements all the functionality except asssigning values. And speed is not an issue for my application. Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: learning unit testing in python
> Hi all. > > I'd like learn some basic unit testing with python. > I red some articles about different testing framework like unittest or > nose, but I'm a bit confused: what is the best choice? I'm not a > professional developer (I'm a SEO) but I belive that unit testing is a > good and pragmatic way to produce working software, so I'd like to > find something really simple ad straightforward because I don't have > to manage big programming projects. > > Thanks in advance, > > Alex Have you checked out doctest? http://docs.python.org/lib/module-doctest.html It's the best way to add few tests to function or class, you just add them to docstring. Unit tests are somewhat demanding as they usualy require creating another file just for storing them, but are ofcourse more powerful as well. For example, unittest module alows you to execute a section of code before or after each test to initialize values and clean up. Nose module has few extra features, but it can also run test writen for unittest, so it's easy to switch if you find standard library module lacking for your purpose. -- http://mail.python.org/mailman/listinfo/python-list
Re: Storing value with limits in object
Thanks alot. I'm going to use this with few modifications to tailor it to my
needs.
Thumbs up!
> #!/usr/bin/env python
>
> ## VERSION 2
> ##
> ## changelog:
> ## - Uses inheritance from _Limited
> ## - Added _LimitedLong and llong
> ## - limit choose between int, long, and float
>
> class _Limited(object):
>def setlimits(self, lim):
>''' Set the limits and if value is not within limit,
>raise ValueError
>
>The lim argument accepts:
>- An instance of _Limited, from which to copy the limits
>- A two-tuple, which specifies the limits i.e. (min, max)
>
>If lim isn't those or lim[0] > lim[1], raise
> InvalidLimitsError
>
>Accepting _Limited instance is just for convenience
>'''
>
>if isinstance(lim, _Limited):
>self.min, self.max = lim.limits
>else:
>try:
>self.min, self.max = lim
>if self.min > self.max: raise ValueError
>except (ValueError, TypeError):
>raise self.InvalidLimitsError, ('limit = %s' %
> str(lim))
>
>if not (self.min < self < self.max):
>raise ValueError, \
> ('val = %s, min = %s, max = %s' % \
> (self, self.min, self.max))
>
>def getlimits(self):
>return (self.min, self.max)
>
>limits = property(getlimits, setlimits)
>
> class _LimitedInt(int, _Limited):
>def __init__(self, value, base = 10):
>int.__init__(value, base)
>
> class _LimitedLong(long, _Limited):
>def __init__(self, value, base = 10):
>long.__init__(value, base)
>
> class _LimitedFloat(float, _Limited):
>def __init__(self, value):
>float.__init__(value)
>
>
> def lint(value, limits, base = None):
>''' Always Creates _LimitedInt instance, allows the use of base
>'''
>if base:
>ret = _LimitedInt(value, base)
>else:
>ret = _LimitedInt(value)
>
>ret.limits = limits
>return ret
>
> def llong(value, limits, base = None):
>''' Always Creates _LimitedLong instance, allows the use of base
>'''
>if base:
>ret = _LimitedLong(value, base)
>else:
>ret = _LimitedLong(value)
>
>ret.limits = limits
>return ret
>
> def lfloat(value, limits):
>''' Always Creates _LimitedFloat instance
>'''
>ret = _LimitedFloat(value)
>
>ret.limits = limits
>return ret
>
> def limit(value, limits):
>''' Automatically choose between _LimitedInt, _LimitedLong,
>or _LimitedFloat. Cannot use _LimitedInt's/Long's base
>'''
>if isinstance(value, (int, long)):
>try:
>ret = _LimitedInt(value)
>except OverflowError:
>ret = _LimitedLong(value)
>elif isinstance(value, float):
>ret = _LimitedFloat(value)
>
>ret.limits = limits
>return ret
--
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Re: Working with graphs - Kevin Bacon game
Thank You for your answer, I fixed everything as You said. -- https://mail.python.org/mailman/listinfo/python-list
Re: Working with graphs - Kevin Bacon game
Thank You for Your answer, I am not sure what to try anymore, I guess I have to return "ime" from __slots__ at cvor() class to show proper strings and I am not able to do it. Now I am not sure that I am going at right direction to do Kevin Bacon game and will I be able to load this data into graph and find shortest way? -- https://mail.python.org/mailman/listinfo/python-list
Re: Working with graphs - Kevin Bacon game
I get it now, basically you are accessing class atributes with "self.something", thank You. So now I get this: "['Apollo 13 (1995)', 'Bill Paxton', 'Tom Hanks', 'Kevin Bacon\n', 'Begyndte ombord, Det (1937)', 'Aage Schmidt', 'Valso Holm\n', 'Bersaglio mobile (1967)', 'Dana Young', 'Bebe Drake\n', 'Bezottsovshchina (1976)', 'Yelena Maksimova', 'Lev Prygunov\n', 'Dark, The (1979)', 'Angelo Rossitto', 'William Devane\n', 'Death to Smoochy (2002)',..." That is great. What would be the best way now to find shortest path between ex. Tom Hanks and ex. William Devane? I should get something like: https://oracleofbacon.org/ Should I insert this data into networkx somehow, would it be easier? -- https://mail.python.org/mailman/listinfo/python-list
