How can I create a dict that sets a flag if it's been modified
I can think of several messy ways of making a dict that sets a flag if it's been altered, but I have a hunch that experienced python programmers would probably have an easier (well maybe more Pythonic) way of doing this. It's important that I can read the contents of the dict without flagging it as modified, but I want it to set the flag the moment I add a new element or alter an existing one (the values in the dict are mutable), this is what makes it difficult. Because the values are mutable I don't think you can tell the difference between a read and a write without making some sort of wrapper around them. Still, I'd love to hear how you guys would do it. Thanks, -Sandra -- http://mail.python.org/mailman/listinfo/python-list
How can I make a dictionary that marks itself when it's modified?
It's important that I can read the contents of the dict without flagging it as modified, but I want it to set the flag the moment I add a new element or alter an existing one (the values in the dict are mutable), this is what makes it difficult. Because the values are mutable I don't think you can tell the difference between a read and a write without making some sort of wrapper around them. Still, I'd love to hear how you guys would do it. Thanks, -Sandra -- http://mail.python.org/mailman/listinfo/python-list
Re: how do real python programmers work?
I'm not an experienced python programmer, but I come from a C++ background as well. I like to code in Komodo ($29 for the personal edition) and that lets me have multiple python files opened in tabs, and multiple interpreters opened below, since the interpreter is command based, it doesn't have to be very tall, and I find this works great (the debugging windows also appear down at the bottom, which is convienient. The debugger alone is worth the $29, within a week or two of serious development and you've paid for the software in terms of saved time.) Komodo runs on windows and linux. This leaves my second screen free, where I keep all my web browsers, with comp.lang.python, gmail, and all the documentation I need. I also keep a macros.py file in a place where it's in the python path, and keep it open in Komodo. Anything I find myself typing over and over in the interpreters, I simply make into a function in the macros file and then reload the macros module and call it. I work with mod_python a lot, so I have a macro that reads in the last 10 lines or so of the apache error log, removes extraneous information and prints them, huge timesaver. -Sandra -- http://mail.python.org/mailman/listinfo/python-list
Re: How can I make a dictionary that marks itself when it's modified?
Thanks to everyone who posted comments or put some thought into this problem. I should have been more specific with what I want to do, from your comments the general case of this problem, while I hate to say impossible, is way more trouble than it's worth. By modified I meant that the dictionary has been changed from its original (constructed) state by either: 1) A new element was added 2) An existing element was changed I want to wrap a dictionary of cookies in mod_python. Cookies are represented as objects with no methods. In light of this and Michael's excellent post, I came up with the following code. class CookieCollection(dict): def __init__(self, d): for k, v in d: v.__setattr__ = self.__wrap_setattr(v.__setattr__) self[k] = v self.modified = False def __setitem__(self, key, value): super(dict, self).__setitem__(key, value) self.modified = True # we don't have to wrap this item, the dict is modified, and can't ever be unmodified def __wrap_setattr(self, real_setattr): def setattr(attrname, val): self.modified = True real_setattr(attrname, val) return setattr def send(self, req): if self.modified: for cookie in req.cookies.values(): Cookie.add_cookie(req, cookie) The purpose of which is to be able to store any cookies sent with the request in the CookieCollection, and then automatically call send() before the headers are finished being sent and it will only do something if the cookies have been altered (otheriwse they don't need to be sent again.) I haven't tested the code yet, but the general idea should be correct at the very least I think. Thanks again, -Sandra -- http://mail.python.org/mailman/listinfo/python-list
How can I test if an argument is a sequence or a scalar?
I want to be able to pass a sequence (tuple, or list) of objects to a function, or only one. It's easy enough to do: isinstance(var, (tuple, list)) But I would also like to accept generators. How can I do this? Anything else is assumed to be a single value (my fault if I pass a dict or something else to the function) and I make it into a tuple with a single value (var, ) in order to simplify the algorithm (wasn't there a special name for a one item tuple? Its been a while since I've programmed in Python.) Is there an easy way to do that? Thanks, -Sandra -- http://mail.python.org/mailman/listinfo/python-list
Re: How can I test if an argument is a sequence or a scalar?
Hi Jean-Paul, Thank you for the advice, I appreciate it, my university training was next to useless so I learn how to write good programs by the advice of helpful people in online communities. I'm really thankfull when people take the time to tell me when I'm doing something wrong and show me a better way. And I was still curious, so thank you for explaining how to distinguish iterables from non-iterables. Have a great day! -Sandra -- http://mail.python.org/mailman/listinfo/python-list
Re: How can I test if an argument is a sequence or a scalar?
Hi Jean-Paul, Thank you for the advice, I appreciate it, my university training was next to useless so I learn how to write good programs by the advice of helpful people in online communities. I'm really thankfull when people take the time to tell me when I'm doing something wrong and show me a better way. And I was still curious, so thank you for explaining how to distinguish iterables from non-iterables. Have a great day! -Sandra -- http://mail.python.org/mailman/listinfo/python-list
