🌐 Mailman 3 July 2018 - Python-list - python.org

Python in the news
by Rich Shepard July 25, 2018

July 25, 2018

The lead article in science section and technology section of this week's 'The Economist' is about Python: <https://www.economist.com/science-and-technology/2018/07/21/python-has-brou…> Enjoy, Rich

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Re: Format list of list sub elements keeping structure.
by Sayth Renshaw July 25, 2018

July 25, 2018

> > Well, your code was close. All you needed was a little tweak > to make it work like you requested. So keep working at it, > and if you have a specific question, feel free to ask on the > list. > > Here's a tip. Try to simplify the problem. Instead of > looping over a list of lists, and then attempting to do a > format in the middle of an iteration, a format that you > really don't know how to do in a vacuum (no pressure, > right???), pull one of the sublists out and try to format it > _first_. IOWs: isolate the problem. > > And, when you can format _one_ list the way you want -- > spoiler alert! -- you can format an infinite number of lists > the way you want. Loops are cool like that. Well, most of > the time. > > The key to solving most complex problems is to (1) break > them down into small parts, (2) solve each small part, and > (3) assemble the whole puzzle. This is a skill you must > master. And it's really not difficult. It just requires a > different way of thinking about tasks. Thank you Rick, good advice. I really am enjoying coding at the moment, got myself and life in a good headspace. Cheers Sayth

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Re: Format list of list sub elements keeping structure.
by Sayth Renshaw July 24, 2018

July 24, 2018

> > Then using this cool answer on SO [...] > > Oh. I thought you wanted to learn how to solve problems. I had no idea you were auditioning for the James Dean part. My bad. Awesome response burn lol. I am trying to solve problems. Getting tired of dealing with JSON and having to figure out the structure each time. Just want to automate that part so I can move through the munging part and spend more time on higher value tasks. Cheers Sayth

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Re: Checking whether type is None
by Rob Gaddi July 24, 2018

July 24, 2018

On 07/24/2018 01:07 PM, Chris Angelico wrote: > On Wed, Jul 25, 2018 at 5:33 AM, Tobiah <toby(a)tobiah.org> wrote: >> Consider: >> >> >>> type({}) is dict >> True >> >>> type(3) is int >> True >> >>> type(None) is None >> False >> >> Obvious I guess, since the type object is not None. >> So what would I compare type(None) to? >> >> >>> type(None) >> <type 'NoneType'> >> >>> type(None) is NoneType >> Traceback (most recent call last): >> File "<stdin>", line 1, in <module> >> NameError: name 'NoneType' is not defined >> >> >> I know I ask whether: >> >> >>> thing is None >> >> but I wanted a generic test. >> I'm trying to get away from things like: >> >> >>> type(thing) is type(None) >> >> because of something I read somewhere preferring >> my original test method. > > There is nothing more generic in a type test than in simply saying "is > None". There are no other instances of NoneType. Don't try > type-checking None; just check if the object is None. > > ChrisA > I suppose one valid usage would be this sort of thing: fn = { int: dispatchInt, str: dispatchStr, list: dispatchList, type(None): dispatchNone }[type(x)] fn(x) -- Rob Gaddi, Highland Technology -- www.highlandtechnology.com Email address domain is currently out of order. See above to fix.

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Re: Format list of list sub elements keeping structure.
by Sayth Renshaw July 24, 2018

July 24, 2018

> myjson = ... > path = "['foo']['bar'][42]" > print(eval("myjson" + path)) > > ? > > Wouldn't it be better to keep 'data' as is and use a helper function like > > def get_value(myjson, path): > for key_or_index in path: > myjson = myjson[key_or_index] > return myjson > > path = ['foo', 'bar', 42] > print(get_value(myjson, path)) > > ? Currently I do leave the data I extract the keys out as a full path. If I use pprint as suggested I get close. ['glossary'], ['glossary', 'title'], ['glossary', 'GlossDiv'], ['glossary', 'GlossDiv', 'title'], ['glossary', 'GlossDiv', 'GlossList'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'ID'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'SortAs'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossTerm'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'Acronym'], ...] But to select elements from the json I need the format json['elem1']['elem2] . I want to be able to get any json in future and parse it into my function and return a list of all json key elements. Then using this cool answer on SO https://stackoverflow.com/a/14692747/461887 from functools import reduce # forward compatibility for Python 3 import operator def getFromDict(dataDict, mapList): return reduce(operator.getitem, mapList, dataDict) def setInDict(dataDict, mapList, value): getFromDict(dataDict, mapList[:-1])[mapList[-1]] = value Then get the values from the keys >>> getFromDict(dataDict, ["a", "r"]) 1 That would mean I could using my function if I get it write be able to feed it any json, get all the full paths nicely printed and then feed it back to the SO formula and get the values. It would essentially self process itself and let me get a summary of all keys and their data. Thanks Sayth

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Re: Non-GUI, single processort inter process massaging - how?
by Chris Green July 24, 2018

July 24, 2018

Dennis Lee Bieber <wlfraed(a)ix.netcom.com> wrote: > On Mon, 23 Jul 2018 22:14:22 +0100, Chris Green <cl(a)isbd.net> declaimed the > following: > > >Anders Wegge Keller <wegge(a)wegge.dk> wrote: > >> > >> If your update frequency is low enough that it wont kill the filesystem and > >> the amount of data is reasonably small, atomic writes to a file is easy to > >> work with: > >> > >Yes, I think you're right, using a file would seem to be the best > >answer. Sample rate is only one a second or slower and there's not a > >huge amount of data involved. > > > > If the data is small enough, putting the file into the small shared > memory (forget if that is /dev/shm or /run/shm on the BBB) would even avoid > wearing out eMMC/SD card. > That is also a very good idea, there's /dev/shm and /run on my BBB, /dev/shm seems to have more space. -- Chris Green ·

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Format list of list sub elements keeping structure.
by Sayth Renshaw July 24, 2018

July 24, 2018

I have data which is a list of lists of all the full paths in a json document. How can I change the format to be usable when selecting elements? data = [['glossary'], ['glossary', 'title'], ['glossary', 'GlossDiv'], ['glossary', 'GlossDiv', 'title'], ['glossary', 'GlossDiv', 'GlossList'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'ID'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'SortAs'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossTerm'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'Acronym'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'Abbrev'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossDef'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossDef', 'para'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossDef', 'GlossSeeAlso'], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossDef', 'GlossSeeAlso', 0], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossDef', 'GlossSeeAlso', 1], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossSee']] I am trying to change it to be. [['glossary'], ['glossary']['title'], ['glossary']['GlossDiv'], ....] Currently when I am formatting I am flattening the structure(accidentally). for item in data: for elem in item: out = ("[{0}]").format(elem) print(out) Which gives [glossary] [title] [GlossDiv] [title] [GlossList] [GlossEntry] [ID] [SortAs] [GlossTerm] [Acronym] [Abbrev] [GlossDef] [para] [GlossSeeAlso] [0] [1] [GlossSee] Cheers Sayth

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Re: Format list of list sub elements keeping structure.
by Sayth Renshaw July 24, 2018

July 24, 2018

On Tuesday, 24 July 2018 14:25:48 UTC+10, Rick Johnson wrote: > Sayth Renshaw wrote: > > > elements = [['[{0}]'.format(element) for element in elements]for elements in data] > > I would suggest you avoid list comprehensions until you master long-form loops. I actually have the answer except for a glitch where on list element is an int. My code for item in data: out = '[{0}]'.format("][".join(item)) print(out) which prints out [glossary] [glossary][title] [glossary][GlossDiv] [glossary][GlossDiv][title] [glossary][GlossDiv][GlossList] .... However, in my source I have two lines like this ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossDef', 'GlossSeeAlso', 0], ['glossary', 'GlossDiv', 'GlossList', 'GlossEntry', 'GlossDef', 'GlossSeeAlso', 1], when it hits these lines I get TypeError: sequence item 6: expected str instance, int found Do I need to do an explicit check for these 2 cases or is there a simpler way? Cheers Sayth

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Re: Format list of list sub elements keeping structure.
by Sayth Renshaw July 24, 2018

July 24, 2018

On Tuesday, 24 July 2018 14:25:48 UTC+10, Rick Johnson wrote: > Sayth Renshaw wrote: > > > elements = [['[{0}]'.format(element) for element in elements]for elements in data] > > I would suggest you avoid list comprehensions until you master long-form loops. My general issue is that I want to pick up all the elements in each sublist and operate on them to concatenate them together. However, using for loops I get each list then each element of each list. When in my head I want each list then all elements of each list. Sayth

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Re: Format list of list sub elements keeping structure.
by Sayth Renshaw July 24, 2018

July 24, 2018

> > > > for item in data: > > for elem in item: > > out = ("[{0}]").format(elem) > > print(out) > > Hint: print implicitly adds a newline to the output string. So collect all the values of each sublist and print a line-at-time to output, or use the end= argument of Py3's print, or find another solution. Also remember that indention is significant in Python. Thanks Getting closer. answer = [] for item in data: for elem in item: out = ("[{0}]").format(elem) answer.append(out) print(answer) Think I need to bring it in a list not an element of a list and process it. Cheers Sayth

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