Box: Python dictionaries with recursive dot notation access • Hacker News Board

Re: Box: Python dictionaries with recursive dot notation access

#101

Post by dragonwriter » Fri, May 05, 2017, 11:10 PM UTC

user5994461 wrote: post #85

aidos wrote: post #74

Earlier quoted context omitted.

Agreed. This is not the sort of code you want to be dealing with in a few years time. Also, I seldom find that string based dicts are what I need. One of the best things about Python is being able to use virtually anything as a key.

> One of the best things about Python is being able to use virtually anything as a key. I find that to be the thing one of the worst thing ever made into a programming language. You are facing a program/API/library and you can have absolutely no clue of what it will give or expect without extensive reverse engineering.

> You are facing a program/API/library and you can have absolutely no clue of what it will give or expect without extensive reverse engineering.

Or reading the docs.

Re: Box: Python dictionaries with recursive dot notation access

#102

Post by msellout » Fri, May 05, 2017, 11:23 PM UTC

Karunamon wrote: post #54

sevensor wrote: post #47

Earlier quoted context omitted.

The annoyance here is a feature not a bug. Deeply nested dictionaries, in my experience, are a source of infinite KeyErrors. The problem with using a dictionary as a cheap object is that it's very easy for it to be an object you weren't expecting. Don't nest dictionaries in Python!

So then what are you supposed to deserialize nested data structures like JSON into? Dictionaries are the obvious "right" way, Python's annoying tooling aside.

What do you think of this library: https://github.com/selik/destructure

It'll enforce schema and destructure the nested dict/list that results from JSON decoding.

Re: Box: Python dictionaries with recursive dot notation access

#103

Post by sampwing » Fri, May 05, 2017, 11:24 PM UTC

If all you want is the dot and indexing syntactic sugar:

  class Box(dict):
    def __init__(self, **kwargs)
      super(Box, self).__init__(kwargs)
      self.__dict__.update(kwargs)

Re: Box: Python dictionaries with recursive dot notation access

#104

Post by xapata » Fri, May 05, 2017, 11:28 PM UTC

Karunamon wrote: post #54

sevensor wrote: post #47

Earlier quoted context omitted.

The annoyance here is a feature not a bug. Deeply nested dictionaries, in my experience, are a source of infinite KeyErrors. The problem with using a dictionary as a cheap object is that it's very easy for it to be an object you weren't expecting. Don't nest dictionaries in Python!

So then what are you supposed to deserialize nested data structures like JSON into? Dictionaries are the obvious "right" way, Python's annoying tooling aside.

That's like asking, "What data structure should I use for this CSV file?"

Depends on the usage. Sometimes you leave them as nested dictionaries and lists. Sometimes you transform them into tabular data. Sometimes you aggregate, etc.

Re: Box: Python dictionaries with recursive dot notation access

#105

Post by cjhanks » Fri, May 05, 2017, 11:31 PM UTC

smoe wrote: post #93

cjhanks wrote: post #86

Earlier quoted context omitted.

There are quite a few nay-votes here, so I'll give a yay vote. In the past I have had to deal with very complex configuration systems; several thousands of lines of XML which were supposed to direct many applications. And writing: value['this']['that']['the_other'] vs value.this.that.the_other Really starts to matter for code legibility. Of course if you change your XML configs your Python will break - but it would l…

I see the value in the latter for code legibility. My gripe with it is, when I'm new to a project that uses a dict implementation like that: how do I know what happens if for example `that` is missing? Does it raise AttributeError, KeyError or just return None? Personally I'd prefer a helper functions like deep_get(dict_, dotted_path[, default]) -> value You stil have to check the docs/source what exactly happens, bu…

Personally I try to implement it as an AttributeError, it seems the most intuitive. By the way, I do understand your point and it's pretty valid in a lot of cases.

Re: Box: Python dictionaries with recursive dot notation access

#106

Post by cjhanks » Fri, May 05, 2017, 11:35 PM UTC

Varriount wrote: post #95

cjhanks wrote: post #86

Earlier quoted context omitted.

There are quite a few nay-votes here, so I'll give a yay vote. In the past I have had to deal with very complex configuration systems; several thousands of lines of XML which were supposed to direct many applications. And writing: value['this']['that']['the_other'] vs value.this.that.the_other Really starts to matter for code legibility. Of course if you change your XML configs your Python will break - but it would l…

What do you typically use for enforcing a schema? I've been using Good[0], however since it is meant for general data structures, users don't get line/column printouts for invalid data. [0] https://pypi.python.org/pypi/good/0.0.7-0

I like jsonschema [1][2], primarily because it's a cross-language standard. Though, I have never used `Good` - it seems to be pretty nice if you're Python focused.

[1] https://pypi.python.org/pypi/jsonschema

[2] http://json-schema.org/

Re: Box: Python dictionaries with recursive dot notation access

#107

Post by msellout » Sat, May 06, 2017, 12:04 AM UTC

Varriount wrote: post #95

cjhanks wrote: post #86

Earlier quoted context omitted.

There are quite a few nay-votes here, so I'll give a yay vote. In the past I have had to deal with very complex configuration systems; several thousands of lines of XML which were supposed to direct many applications. And writing: value['this']['that']['the_other'] vs value.this.that.the_other Really starts to matter for code legibility. Of course if you change your XML configs your Python will break - but it would l…

What do you typically use for enforcing a schema? I've been using Good[0], however since it is meant for general data structures, users don't get line/column printouts for invalid data. [0] https://pypi.python.org/pypi/good/0.0.7-0

Give `destructure` a try https://github.com/selik/destructure

Re: Box: Python dictionaries with recursive dot notation access

#108

Post by zubat » Sat, May 06, 2017, 12:14 AM UTC

jerf wrote: post #58

I think every Python programmer implements this at some point. I think the real reason not to do this is one that as of this writing still hasn't been mentioned yet, which is that when using dot notation, your key names have to fit the Python grammar for identifiers, so you can't have a key "the thing" with a space, or anything else that isn't a Python identifier. So you can't just say "I can access this dictionary w…

I ended up making a custom data structure and query language around this kind of notation. Not in Python(am working in Haxe) but easily generalized. The structure is either array or string map or ordered string map with a dynamic data field and optional string tags. So it maps very well onto JSON or XML style data, but comes with the benefit of a very unambiguous way to do queries, where I can mix together addressing styles(take this numbered index OR take the named key) and pull elements into an array without much difficulty. The lookup syntax is "@#..." and each key or index entry is parsed into an ADT. I can pass along partially constructed queries as the relevant data to be processed. It's not quite as flexible as SQL since the data has to come in tree form, but it creates a major design affordance: the same query can be passed to a custom algorithm or custom data structure, with less ambiguity than a simple string lookup.

To some extent this retreads ground covered by e.g. XPath, but the specific structure puts it closer to my day-to-day needs.

Re: Box: Python dictionaries with recursive dot notation access

#109

Post by Retra » Sat, May 06, 2017, 12:39 AM UTC

xapata wrote: post #100

mannykannot wrote: post #80

Earlier quoted context omitted.

>I may not even know where the manual is when a fancy wrapper dumps a trace. I read somewhere that if it is written in self-documenting code, the problem and its solution will be obvious.

Was that sarcasm? What counts as "self-documenting"?

Undocumented code is self-documenting. Because it only ever does exactly what is written, it must be intended to do exactly what it does.

Re: Box: Python dictionaries with recursive dot notation access

#110

Post by Retra » Sat, May 06, 2017, 12:49 AM UTC

yeukhon wrote: post #21

crdoconnor wrote: post #18

Earlier quoted context omitted.

"I like Python a lot, and I don't write much Javascript, but one thing I wish I could do in Python is the dot notation from a dictionary" Why though?

Because it saves me a lot of chars. foo['name']['attr1']['attr2']['morefuckingattr'] vs foo.name.atr1.attr2.morefuckingattr More of a personal preference.

Personally, I only use hard-coded strings like that for shallow nesting. If I need to index 4 layers deep, something down there is going to be turned into an object, otherwise enumerating all the possible keys to ensure the code is correct becomes a nightmare. And once you do that, you can use dot notation anyway.