Ah, good point. I assumed shelve was more or less identical to pickle, but clearly haven't used it enough to tell the difference.
On 4 February 2014 09:07, Justin Israel <[email protected]> wrote: > A few more bits about shelve vs json. shelve is actually not > a serialization format specifically, but rather a key-value store that > serializes its values using pickle. It stores like a database and has the > added benefit of letting you modify in-memory, piecemeal over time, until > it gets flushed to disk. Basically it acts just like optionVar, by being > accessible like a dictionary, as opposed to needing to dump your entire > structure to and from disk with each change. > > And also, json has a "dump" variant: > > with open(fname, 'w') as f: > # writes directly to your file > json.dump(data, f) > > If you use Qt at all, there is also a really nice class called > QSettings<http://srinikom.github.io/pyside-docs/PySide/QtCore/QSettings.html> > which > acts similar to the shelve module, but also has the benefit of knowing the > cross-platform location to store user preferences, and is completely safe > for concurrent reads/writes between threads/processes. > > > > > > > On Tue, Feb 4, 2014 at 8:46 PM, Marcus Ottosson <[email protected]>wrote: > >> I take it you are looking to store data from code onto disk for retrieval >> later with libraries external to Maya, or even outside of Maya. >> >> This is usually a two-step process: >> 1. Serialization <http://en.wikipedia.org/wiki/Serialization>, which >> means to make a set of data - in this case, internal to Python - writeable >> to disk and retrievable later. >> 2. Writing to disk. >> >> Depending on your needs, you may not need serialization and can simply >> write data structures directly to disk; e.g. if you are looking to store >> text. >> >> >> with open(file, 'w') as f: >> >> f.write(my_text) >> >> >> >> with open(file, 'r') as f: >> >> retrieved_text = f.read() >> >> Serialization comes in many flavours and are relevant if you're looking >> to store more complex types, such as list, dict or arbitrary data >> structures of your own or Python's making. >> >> The shelve <http://docs.python.org/2/library/shelve.html> module as >> suggested above is appropriate if the data you're storing involves any >> objects other than the plain-old-data types, such as string, int, booletc. >> >> If you're needs are simpler, an alternative to shelve is >> json<http://docs.python.org/2/library/json.html>, >> also included in the standard library, but capable of storing only >> plain-old-data. >> >> Both shelve and json come with their own writing mechanism, but in the >> case of json, the resulting serialized data is of type string and can be >> passed around and modified in code before being written out by other means. >> >> >> serialized_data = json.dumps(my_data) >> >> with open(file, 'w') as f: >> >> f.write(serialized_data) >> >> Which brings me to the next important topic of which json and shelve are >> good examples. >> >> One results in human-readable data and the other does not. Generally, >> human-readable data lacks the performance of binary equivalents but make up >> for it in that they can be inspected and edited by humans. It all depends >> on your needs, really. >> >> See here for a summary of what Python has to offer in this aspect >> http://docs.python.org/2/library/persistence.html >> >> >> >> On 4 February 2014 05:48, Chad Dombrova <[email protected]> wrote: >> >>> I *think* that Glom was looking for something similar to optionVars for >>> use outside of Maya, but I could be wrong. >>> — >>> Sent from Mailbox <https://www.dropbox.com/mailbox> for iPhone >>> >>> >>> On Mon, Feb 3, 2014 at 8:43 PM, Count Zer0 <[email protected]> wrote: >>> >>>> PyMel gives you easy access to them too: >>>> >>>> >>>> http://download.autodesk.com/global/docs/maya2013/en_us/PyMel/generated/classes/pymel.core.language/pymel.core.language.OptionVarDict.html >>>> >>>> And you should be using PyMel anyway if you're moving past MEL anyway. >>>> >>>> -jason >>>> >>>> On Monday, February 3, 2014 9:21:44 AM UTC-8, Glom De wrote: >>>>> >>>>> hi guys >>>>> as you know ,maya command "optionVar" can store variables in disk, >>>>> are there any functions or Module of python can do same thing like >>>>> Maya cmd "optionVar" >>>>> >>>>> googled ， but did not find any clue。。。。。 >>>>> anyone can give me some info about that, thanks a lot!!! >>>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Python Programming for Autodesk Maya" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/python_inside_maya/1cf36bfc-4066-4a6c-acd0-860ecd33b765%40googlegroups.com >>>> . >>>> For more options, visit https://groups.google.com/groups/opt_out. >>>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Python Programming for Autodesk Maya" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/python_inside_maya/1391492891930.317b607f%40Nodemailer >>> . >>> >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >> >> >> >> -- >> *Marcus Ottosson* >> [email protected] >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Python Programming for Autodesk Maya" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/python_inside_maya/CAFRtmOAAepsjw_wDVgOF5yDbP5Mn9MOtUrVtNMFNktbzQ_cAcw%40mail.gmail.com >> . >> >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- > You received this message because you are subscribed to the Google Groups > "Python Programming for Autodesk Maya" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/python_inside_maya/CAPGFgA0NAU4q53EJydpwbuHxc-UrCZ%2BJGChcykVoBKLdrOioMw%40mail.gmail.com > . > > For more options, visit https://groups.google.com/groups/opt_out. > -- *Marcus Ottosson* [email protected] -- You received this message because you are subscribed to the Google Groups "Python Programming for Autodesk Maya" group. 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