Re: Linq to Python
2008/9/24 Duncan Booth [EMAIL PROTECTED]: Python still wins hands down on this example both in verbosity and readability: But AFAICS, the Python version you give creates a temporary. One of the advantages cited for LINQs functional programming paradigm is that it specifies what is wanted at a higher level, so the compiler can decide whether to create temporaries, and can also decide whether to farm the thing off to multiple processors -- harder if you've specified in detail /how/ to do the job. Not an issue for little jobs, but certainly an issue for, for example, a friend who had a daily database job to do that took over 24 hours to run. I haven't yet had occasion to use LINQ in anger yet, so I have no idea whether its an idea to love or to hate. I do think it is good that C# has effectively sprouted list comprehensions (not to mention anonymous types and type inferencing) and I expect there may be some aspects worth looking at for Python but I think they are more likely to lead to itertools functions than extensions to syntax. Yes, looking at what LINQ adds to C# (according to http://msdn.microsoft.com/en-gb/library/bb397909.aspx): - Implicitly typed variables: Python already has. - Object and collection initialisers: Not sure whether Python can do this directly, but it can certainly emulate it with a dictionary. - Anonymous types: Not sure whether Python can do this directly, but it can certainly emulate it with a dictionary. - Extension methods: Python already has. - Lambda expressions: Python already has. - Auto-Implemented properties: No, but that's just syntactic sugar to make declarations more compact. So all of the language elements that are needed for LINQ are already in Python; a library should do the trick. -- Tim Rowe -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Tim Rowe [EMAIL PROTECTED] wrote: I haven't yet had occasion to use LINQ in anger yet, so I have no idea whether its an idea to love or to hate. I do think it is good that C# has effectively sprouted list comprehensions (not to mention anonymous types and type inferencing) and I expect there may be some aspects worth looking at for Python but I think they are more likely to lead to itertools functions than extensions to syntax. Yes, looking at what LINQ adds to C# (according to http://msdn.microsoft.com/en-gb/library/bb397909.aspx): - Implicitly typed variables: Python already has. - Object and collection initialisers: Not sure whether Python can do this directly, but it can certainly emulate it with a dictionary. - Anonymous types: Not sure whether Python can do this directly, but it can certainly emulate it with a dictionary. - Extension methods: Python already has. - Lambda expressions: Python already has. - Auto-Implemented properties: No, but that's just syntactic sugar to make declarations more compact. So all of the language elements that are needed for LINQ are already in Python; a library should do the trick. Not quite. The C# implementation of lambda expressions has a neat trick that is central to LINQ. A lambda expression compiles either to executable code, or to an expression tree. If you are filtering some C# sequence object then (as with Python lambdas) the LINQ code simply calls the compiled lambda expression like any other delegate, but if you are filtering a SQL lookup the LINQ code gets an expression syntax tree and further compiles it (at runtime) into SQL code to perform the filtering at the database level. Python can't do the compile time matching to vary what it produces according to how the lambda is used, but it would be perfectly possible for function objects which are compiled from a lambda expression to grow an extra attribute that would hold an AST for the expression. That way you could write code that took a filter function and, if it had the AST attribute available, compiled it to SQL or xpath or whatever else you fancied. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
sturlamolden [EMAIL PROTECTED] wrote: On Sep 24, 10:59 pm, Duncan Booth [EMAIL PROTECTED] wrote: Simple LINQ expressions like the one you gave map easily to Python list comprehensions. What Microsoft have done though is provide a consistent implementation which allows you to write complex SQL like expressions whi ch will work identically on databases or most other sequence types. han extensions to syntax. List comprehensions work with any iterable sequence. You can nest them to make more complex statements. You can also use a generator to iterate through a database or an XML document. Here is approximately where linq stops being a marvelous addition to Python. A lot of what LINQ does is already easy to do in Python, and most of the rest can probably be added fairly easily, but it does provide a consistent framework which may make it easier to do complex LINQ statements than complex list comprehensions. BTW, a minor correction: LINQ statements are closer to generators, not list comprehensions. They don't actually evaluate their results until you iterate over them and you can re-used the same LINQ statement multiple times getting different results if the data has changed. And I can honestly do without the SQL syntax. snap :) -- Duncan Booth http://kupuguy.blogspot.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On 25 Sep, 10:08, Duncan Booth [EMAIL PROTECTED] wrote: A lot of what LINQ does is already easy to do in Python, and most of the rest can probably be added fairly easily, but it does provide a consistent framework which may make it easier to do complex LINQ statements than complex list comprehensions. Yes, that's the word, consistent framework. I wonder what that means? Do you mean Python syntax is inconsitent? BTW, a minor correction: LINQ statements are closer to generators, not list comprehensions. They don't actually evaluate their results until you iterate over them and you can re-used the same LINQ statement multiple times getting different results if the data has changed. Python has generator expressions with the same syntax as list comprehensions, except you use () instead of []. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi
If i rephrase my question how will i do this in Python
http://informationr.net/ir/13-2/TB0806.html
Watch this query on the page Where he joins all different kind of things with
ease and elegance(as per my opinion)
[code]
var stoogeGuys =
Beginning with the XML source
from xmlGuys in xmlSource.Descendants(Stooge)
Join to the array on the common element stoogeName
join arrayGuys in familyFacts
on xmlGuys.Element(stoogeName).Value equals arrayGuys.stoogeName
Join to the database on the common element stoogeName
join dbGuys in stoogeContext.stoogeTables
on xmlGuys.Element(stoogeName).Value equals dbGuys.stoogeName
select new
{
firstName= dbGuys.stoogeName,
familyName = arrayGuys.familyName,
birthDate= xmlGuys.Element(birthDate).Value,
deathDate= xmlGuys.Element(deathDate).Value,
hairCutStyle = dbGuys.stoogeHaircut,
};
[/code]
regards
Hrishy
--
http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi Grant haha :-) i discounted that perspective :-) regards Hrishy --- On Thu, 25/9/08, Grant Edwards [EMAIL PROTECTED] wrote: From: Grant Edwards [EMAIL PROTECTED] Subject: Re: Linq to Python To: python-list@python.org Date: Thursday, 25 September, 2008, 2:22 AM On 2008-09-24, Bruno Desthuilliers [EMAIL PROTECTED] wrote: hrishy a écrit : (snip) I apologise (I thought Python programmers were smart and they did know what LINQ was) Is there really any relation between being smart and knowing anything about the latest MS fad ? God, I hope not -- or I'd rather be stupid. -- Grant -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi Roger I am impressed (i always suspected Python programmers are smart no doubt about it). But what about the case where they join different sources like the one here http://informationr.net/ir/13-2/TB0806.html Thanks for teaching me :-) i am thankful for that regards Hrishy names = [Burke, Connor, Frank, Everett, Albert, George, Harris, David] result = [each.upper() for each in names if len(each) == 5] result.sort() for each in result: print each Yes clearly 'the Python crowd' must admit LINQ is 'much better', I'm sold, in fact off to download my Free, but limited editions of Visual Studio 2005 for a single programming language supported by .NET right away! OK so maybe I'm being naive here but it looks to me like this new paradigm's big idea is to use a python + SQL type syntax to access data in random objects. Big whoop. It's not that difficult to write a generators that wraps XML files and databases is it? What am I missing here? Roger Heathcote. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On 25 Sep, 12:06, hrishy [EMAIL PROTECTED] wrote:
var stoogeGuys =
Beginning with the XML source
from xmlGuys in xmlSource.Descendants(Stooge)
Join to the array on the common element stoogeName
join arrayGuys in familyFacts
on xmlGuys.Element(stoogeName).Value equals arrayGuys.stoogeName
Join to the database on the common element stoogeName
join dbGuys in stoogeContext.stoogeTables
on xmlGuys.Element(stoogeName).Value equals dbGuys.stoogeName
select new
{
firstName = dbGuys.stoogeName,
familyName = arrayGuys.familyName,
birthDate = xmlGuys.Element(birthDate).Value,
deathDate = xmlGuys.Element(deathDate).Value,
hairCutStyle = dbGuys.stoogeHaircut,
};
[/code]
That is a for loop over xmlGuys in xmlSource.Descendants(Stooge).
Those joins are e.g. dictionary lookups, and finally an object with
names, birthdates, etc. are appended to the list stoogeGuys.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi Tim I am not a LINQ expert just a LINQ user and (was a little envious why the langauge i fantasize doesnt have it (pardon my ignorance of python)) LINQ as far as i know allows you to query all sources using a consistent interface . You can query a message queue ,xml document ,array object or relational source by learning LINQ and even join them as illustrated below http://informationr.net/ir/13-2/TB0806.html If somebody can tutor me how i can do that in python that would be great (and mayeb satisfy my greed and leave me with a happy feeling that my langauge python can do it) regards Hrishy --- On Wed, 24/9/08, Tim Golden [EMAIL PROTECTED] wrote: From: Tim Golden [EMAIL PROTECTED] Subject: Re: Linq to Python To: Cc: python-list@python.org Date: Wednesday, 24 September, 2008, 8:20 PM [EMAIL PROTECTED] wrote: sturlamolden: No, because Python already has list comprehensions and we don't need the XML buzzword. LINQ is more than buzzwords. Python misses several of those features. So maybe for once the Python crowd may recognize such C# feature as much better than things present in Python. Said that, I presume Python will go on as usual, and LINQ-like capabilities will not be integrated in Python. In the meantime where I live lot of people will keep using C# instead of Python and CLisp, natural selection at work indeed. Perhaps a quick summary of what LINQ offers which might be integrated into Python would help those of us who are ignorant? (This is a serious comment; I'd like to know). TJG -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On 25 Sep, 12:06, hrishy [EMAIL PROTECTED] wrote:
[code]
var stoogeGuys =
Beginning with the XML source
from xmlGuys in xmlSource.Descendants(Stooge)
Join to the array on the common element stoogeName
join arrayGuys in familyFacts
on xmlGuys.Element(stoogeName).Value equals arrayGuys.stoogeName
Join to the database on the common element stoogeName
join dbGuys in stoogeContext.stoogeTables
on xmlGuys.Element(stoogeName).Value equals dbGuys.stoogeName
select new
{
firstName = dbGuys.stoogeName,
familyName = arrayGuys.familyName,
birthDate = xmlGuys.Element(birthDate).Value,
deathDate = xmlGuys.Element(deathDate).Value,
hairCutStyle = dbGuys.stoogeHaircut,
};
[/code]
It could e.g. look like this in Python:
stoogeGuys = []
for xmlGuys in xmlSource.Descendants[Stooge]:
arrayGuys = familyFacts[xmlGuys.stoogeName]
dbGuys = stoogeContext.stoogeTables[xmlGuys.stoogeName]
stoogeGuys += \
[{'firstName':dbGuys.stoogeName,
'familyName': arrayGuys.familyName,
'birthDate':xmlGuys.birthDate,
'deathDate':dbGuys.deathDate,
'hairCutStyle': dbGuys.stoogeHaircut}]
--
http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi
Pardon my ignorance again but id ont see any join in python or did i miss
something ?
regards
Hrishy
--- On Thu, 25/9/08, sturlamolden [EMAIL PROTECTED] wrote:
From: sturlamolden [EMAIL PROTECTED]
Subject: Re: Linq to Python
To: python-list@python.org
Date: Thursday, 25 September, 2008, 12:02 PM
On 25 Sep, 12:06, hrishy [EMAIL PROTECTED] wrote:
[code]
var stoogeGuys =
Beginning with the XML source
from xmlGuys in
xmlSource.Descendants(Stooge)
Join to the array on the common element
stoogeName
join arrayGuys in familyFacts
on
xmlGuys.Element(stoogeName).Value equals
arrayGuys.stoogeName
Join to the database on the common element
stoogeName
join dbGuys in stoogeContext.stoogeTables
on
xmlGuys.Element(stoogeName).Value equals
dbGuys.stoogeName
select new
{
firstName = dbGuys.stoogeName,
familyName = arrayGuys.familyName,
birthDate =
xmlGuys.Element(birthDate).Value,
deathDate =
xmlGuys.Element(deathDate).Value,
hairCutStyle = dbGuys.stoogeHaircut,
};
[/code]
It could e.g. look like this in Python:
stoogeGuys = []
for xmlGuys in xmlSource.Descendants[Stooge]:
arrayGuys = familyFacts[xmlGuys.stoogeName]
dbGuys = stoogeContext.stoogeTables[xmlGuys.stoogeName]
stoogeGuys += \
[{'firstName':dbGuys.stoogeName,
'familyName': arrayGuys.familyName,
'birthDate':xmlGuys.birthDate,
'deathDate':dbGuys.deathDate,
'hairCutStyle': dbGuys.stoogeHaircut}]
--
http://mail.python.org/mailman/listinfo/python-list
--
http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On 25 Sep, 13:08, hrishy [EMAIL PROTECTED] wrote: Pardon my ignorance again but id ont see any join in python or did i miss something ? It's more Pythonic to use the syntax of dictionary lookups. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi Thank you very much I appreciate taking the pain to explain this to me. regards Hrishy --- On Thu, 25/9/08, sturlamolden [EMAIL PROTECTED] wrote: From: sturlamolden [EMAIL PROTECTED] Subject: Re: Linq to Python To: python-list@python.org Date: Thursday, 25 September, 2008, 12:16 PM On 25 Sep, 13:08, hrishy [EMAIL PROTECTED] wrote: Pardon my ignorance again but id ont see any join in python or did i miss something ? It's more Pythonic to use the syntax of dictionary lookups. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
sturlamolden [EMAIL PROTECTED] wrote:
On 25 Sep, 10:08, Duncan Booth [EMAIL PROTECTED] wrote:
A lot of what LINQ does is already easy to do in Python, and most of
the rest can probably be added fairly easily, but it does provide a
consistent framework which may make it easier to do complex LINQ
statements than complex list comprehensions.
Yes, that's the word, consistent framework. I wonder what that
means? Do you mean Python syntax is inconsitent?
No Python's syntax is fine. The api's aren't as consistent though:
Microsoft added a common set of extension methods which work on
databases, xml, builtin sequences and can be easily extended to include
other custom sequences.
As an example to filter a list in Python you'd use a list comprehension
with an 'if', but for a database you'd probably prefer a select with a
'where' clause so as to avoid retrieving and discarding 99 or your 1
million rows. The apis defined by LINQ allow that sort of optimisation
to happen transparently, the simple list would just test each element
but the database would run an appropriate query.
So what the 'can we have LINQ in Python' people are asking is to be able
to write things like:
x = (c for c in customers if c.id=='123')
and know that they aren't doing a linear search unless that is the best
that can be done. The LINQ equivalent would be something like:
var x = from c in customers where c.id=='123'
select new { c.name, c.id };
which is compiled to:
var x = customers.Where(c = c.id=='123');
and depending on the type of 'customers' the Where method can either get
a callable function to test the condition or an expression tree which it
can compile into another language such as SQL (C# lambdas can compile
either to executable code or to Expression objects that you can
further process).
There's an article at
http://www.interact-sw.co.uk/iangblog/2005/09/30/expressiontrees which
has a real example showing how:
DataContext db = new DataContext(server=.;initial catalog=northwind);
TableOrders orders = db.GetTableOrders();
TableCustomers customers = db.GetTableCustomers();
var q = from o in orders, c in customers
where o.ShipCity == London (o.CustomerID == c.CustomerID)
select new { o.OrderDate, c.CompanyName, c.ContactTitle,
c.ContactName };
actually ends up as a single SQL query:
exec sp_executesql N'SELECT [t1].[CompanyName], [t1].[ContactName],
[t1].[ContactTitle], [t0].[OrderDate]
FROM [Orders] AS [t0], [Customers] AS [t1]
WHERE ([t0].[ShipCity] = @p0) AND ([t0].[CustomerID] = [t1].
[CustomerID])', N'@p0 nvarchar(6)', @p0 = N'London'
BTW, a minor correction: LINQ statements are closer to generators,
not list comprehensions. They don't actually evaluate their results
until you iterate over them and you can re-used the same LINQ
statement multiple times getting different results if the data has
changed.
Python has generator expressions with the same syntax as list
comprehensions, except you use () instead of [].
It might surprise you to know that I have actually come across generator
expressions. :^)
My wording was deliberate: LINQ queries are re-usable, so are Python's
generators, but generator expressions are not. The comparison isn't
exact, you have to call the generator to get an iterator whereas a LINQ
expression gives you something which is directly iterable.
--
Duncan Booth http://kupuguy.blogspot.com
--
http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On 25 Sep, 14:22, Duncan Booth [EMAIL PROTECTED] wrote: No Python's syntax is fine. The api's aren't as consistent though: Microsoft added a common set of extension methods which work on databases, xml, builtin sequences and can be easily extended to include other custom sequences. That is correct, but it is a library issue and cannot be solved by adding new syntax. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Duncan Booth: Microsoft added a common set of extension methods which work on databases, xml, builtin sequences and can be easily extended to include other custom sequences. When the processing is done in memory, LINQ may also work well with multi-core CPUs, see PLINQ. Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi Terry Oops i never realised the mistake i have commited I apologise (i thought changing the subject line would make a new thread) I apologise (I thought Python programmers were smart and they did know what LINQ was) I don't apologise ( i dont apologise for the third one not sounding cocky here but i did google but nothing much came up thats when i posted the question here since i always see Python programmers are somehow smarter then programmers in other langauges i don't know if its the language or the programmers themselves that make them smart) regards Hrishy --- On Tue, 23/9/08, Terry Reedy [EMAIL PROTECTED] wrote: From: Terry Reedy [EMAIL PROTECTED] Subject: Re: Linq to Python To: python-list@python.org Date: Tuesday, 23 September, 2008, 7:51 PM Will LINQ be ported to Python ? I have three suggestions: 1. When starting a new thread, start a *new* thread. Don't tack a new, unrelated subject onto an existing thread. Your post will not be seen by people with readers that collapse thread and who do not happen to read the 'Python is slow?' thread. 2. Also, give enough informaton that people can understand your question without searching the web and guessing. In particular, that do *you* mean by LINQ? The game? The .NET component? Or something else? 3. Before posting, search the Python manuals or the web a bit for an answer. If you mean the .NET component, googling 'Python LINQ' should partly answer your question. tjr -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi Well wouldn't it be a lot easier to query and join a xml source with a relational source with LINQ capabilites in Python. Hmm what am i missing here is there a site that takes all LINQ examples and does them using list comprehensions and makes them sound easy ? wasn't python supposed to make everything easy ? regards Hrishy --- On Tue, 23/9/08, sturlamolden [EMAIL PROTECTED] wrote: From: sturlamolden [EMAIL PROTECTED] Subject: Re: Linq to Python To: python-list@python.org Date: Tuesday, 23 September, 2008, 7:49 PM On Sep 23, 4:48 pm, hrishy [EMAIL PROTECTED] wrote: Will LINQ be ported to Python ? No, because Python already has list comprehensions and we don't need the XML buzzword. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi Tom This is what i like and feel of the Python programmers smarter then every other langauge i know of. But i am not comfortable with your second statement XML i never need it one day everybody would need it. regards Hrishy --- On Tue, 23/9/08, Thomas G. Willis [EMAIL PROTECTED] wrote: From: Thomas G. Willis [EMAIL PROTECTED] Subject: Re: Linq to Python To: python-list@python.org Date: Tuesday, 23 September, 2008, 7:45 PM But surely the idea behind it will eventually spread. It's really just comprehensions generalized over XML and relational datasets, a noble goal. Besides, it's main purpose for .NET was to bring functional programming to it. Python already has that, somewhat... it's really any object out of the box, i think the sql linq stuff is more of a query compiler, IMO sqlalchemy does that. query = select(user_cols, and_(table_relationship.c.accept_user_id==user.id, table_relationship.c.start_date==None ), from_obj=join( table_relationship,table_user, onclause=table_user.c.id==table_relationship.c.init_user_id ).outerjoin(table_profile) ) session.execute(query).fetchall() XML? meh hopefully I would never need it. :) C# is my day job, and when I got my hands on LINQ back in January my initial thought was Finally I have list comprehensions day job is fun again For the most part, I think C# is catching up. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Wed, Sep 24, 2008 at 11:25 AM, hrishy [EMAIL PROTECTED] wrote: Hi Tom This is what i like and feel of the Python programmers smarter then every other langauge i know of. But i am not comfortable with your second statement XML i never need it one day everybody would need it. regards Hrishy Well you may be right which is why I said hopefully one thing I do know is that in my work in both .net and java, XML plays a more significant role. Everyone can probably speculate differently as to why this is. My personal feeling is that it is because XML is less of a hassle than building/passing around class hierarchies for application state in various scenarios.But in python, it is far easier for me to pass around a dict or some similar structure to get roughly the same effect. So in my mind, XML solves a problem that is present in both .net and java, but not necessarily python. In the same way, linq to xml solves the problem of handling xml in a more convenient way. In order for it to be useful in python, the problem that xml solves would have to be present IMO. That's not to say it's not possible. Someone who needs something like LINQ to XML but in python could write something probably similar to what sqlalchemy does and it would require no changes to the python language or runtime. If it was written then maybe people would invent ways to use XML in python that are better than what other things do. Hooray for the free market of ideas. :) This is all my opinion , I have no idea what the conventional wisdom of the python community is on XML, but in my experience in other languages, it seems to be the answer to a question that no one asked, or the wrong answer, more often than it is the appropriate answer. Maybe it's only that way on OHIO. :) -- Thomas G. Willis -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Sep 24, 5:22 pm, hrishy [EMAIL PROTECTED] wrote: Well wouldn't it be a lot easier to query and join a xml source with a relational source with LINQ capabilites in Python. Hmm what am i missing here is there a site that takes all LINQ examples and does them using list comprehensions and makes them sound easy ? wasn't python supposed to make everything easy ? Most Python programmers use other languages as well. I have working knowledge of C, Matlab, C++, Java, Fortran 95, and C#. Those that responded to your post know what LINQ are and what LINQ does. Put simply, Python has dynamic typing, list comprehensions, and is scriptable (i.e. Python source is structured text). That's why Python don't need LINQ and XML the same way as C#. LINQ and XML is needed because C# is a statically typed compiled language. That is: LINQ: Python has list comprehensions and dynamic typing (C# do not) XML: Python is structured text (compiled .NET assemblies are not) Second, minimalistic syntax is a virtue. That is why C is still around. Python don't add new syntax sugar every time Redmond invents a new buzzword. Functions like XML processing are delegated to libraries -- where they belong. Nobody was saying LINQ is a bad idea for a language like C#. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
sturlamolden: No, because Python already has list comprehensions and we don't need the XML buzzword. LINQ is more than buzzwords. Python misses several of those features. So maybe for once the Python crowd may recognize such C# feature as much better than things present in Python. Said that, I presume Python will go on as usual, and LINQ-like capabilities will not be integrated in Python. In the meantime where I live lot of people will keep using C# instead of Python and CLisp, natural selection at work indeed. Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
[EMAIL PROTECTED] wrote: sturlamolden: No, because Python already has list comprehensions and we don't need the XML buzzword. LINQ is more than buzzwords. Python misses several of those features. So maybe for once the Python crowd may recognize such C# feature as much better than things present in Python. Said that, I presume Python will go on as usual, and LINQ-like capabilities will not be integrated in Python. In the meantime where I live lot of people will keep using C# instead of Python and CLisp, natural selection at work indeed. Perhaps a quick summary of what LINQ offers which might be integrated into Python would help those of us who are ignorant? (This is a serious comment; I'd like to know). TJG -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Wed, Sep 24, 2008 at 2:11 PM, [EMAIL PROTECTED] wrote: sturlamolden: No, because Python already has list comprehensions and we don't need the XML buzzword. LINQ is more than buzzwords. Python misses several of those features. So maybe for once the Python crowd may recognize such C# feature as much better than things present in Python. Said that, I presume Python will go on as usual, and LINQ-like capabilities will not be integrated in Python. In the meantime where I live lot of people will keep using C# instead of Python and CLisp, natural selection at work indeed. Why do you swing so widely between being an interesting poster with interesting, useful things to say and mindless trolling? There's a lot of reasons to use C# instead of Python or Lisp (or any other language for that matter), but I can't imagine that someone would make that decision based solely on LINQ. I'd go so far as to say that if they do, I question their professional competence. LINQ is an interesting implementation of an old idea. The place where it differs from list comps is that it has appropriate hooks for the specific linq implementation to override the way results are gathered, and such hooks in Python would be an interesting idea. I've taken a shot and figuring out where and how they should be implemented, but I haven't come up with anything I like. Maybe you should try it? LINQs native object API (not the syntax sugar available in C#) is not very different from Python ORMs. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
[EMAIL PROTECTED] wrote:
sturlamolden:
No, because Python already has list comprehensions and we don't need the XML
buzzword.
LINQ is more than buzzwords. Python misses several of those features.
So maybe for once the Python crowd may recognize such C# feature as
much better than things present in Python.
Said that, I presume Python will go on as usual, and LINQ-like
capabilities will not be integrated in Python. In the meantime where I
live lot of people will keep using C# instead of Python and CLisp,
natural selection at work indeed.
Bye,
bearophile
LOL, I just read that and thought - Ok this sounds serious I'd better go
find out what this LINQ business is all about so I googled.. and ended
up on MSDN where there's impressive sounding talk about how we need a
way to query databases and XML files with a unified syntax like we do
for for standard datatypes like files and arrays. Well yes,that makes
sense I think and proceed to look at their example code, curious as to
what this new paradigm looks like:
using System;
using System.Linq;
using System.Collections.Generic;
class app {
static void Main() {
string[] names = { Burke, Connor, Frank,
Everett, Albert, George,
Harris, David };
IEnumerablestring query = from s in names
where s.Length == 5
orderby s
select s.ToUpper();
foreach (string item in query)
Console.WriteLine(item);
}
}
ROTFLMAO! Wow, what progress they're making! Quick guys let's jump on
before we get left behind - we dont want to miss out on this exciting
and mysterious 'foreach' construct or this strange and exotic sounding
'IEnumerable query' thing. To think that python might someday reach such
lofty heights where we'll be able to simply write...
names = [Burke, Connor, Frank, Everett,
Albert, George, Harris, David]
result = [each.upper() for each in names if len(each) == 5]
result.sort()
for each in result: print each
Yes clearly 'the Python crowd' must admit LINQ is 'much better', I'm
sold, in fact off to download my Free, but limited editions of Visual
Studio 2005 for a single programming language supported by .NET right away!
OK so maybe I'm being naive here but it looks to me like this new
paradigm's big idea is to use a python + SQL type syntax to access data
in random objects. Big whoop. It's not that difficult to write a
generators that wraps XML files and databases is it?
What am I missing here?
Roger Heathcote.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
hrishy a écrit : (snip) I apologise (I thought Python programmers were smart and they did know what LINQ was) Is there really any relation between being smart and knowing anything about the latest MS fad ? -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Sep 24, 9:11 pm, [EMAIL PROTECTED] wrote: In the meantime where I live lot of people will keep using C# instead of Python and CLisp, natural selection at work indeed. Please explain to me what Linq can do that Python does not. Put you emphasis on why this can't be done with a library, and thus will require addition of new syntax to the language. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
r0g [EMAIL PROTECTED] wrote:
OK so maybe I'm being naive here but it looks to me like this new
paradigm's big idea is to use a python + SQL type syntax to access data
in random objects. Big whoop. It's not that difficult to write a
generators that wraps XML files and databases is it?
What am I missing here?
Simple LINQ expressions like the one you gave map easily to Python list
comprehensions. What Microsoft have done though is provide a consistent
implementation which allows you to write complex SQL like expressions which
will work identically on databases or most other sequence types.
Here's another LINQ example:
ListCustomer customers = GetCustomerList();
var customerOrderGroups =
from c in customers
select
new {c.CompanyName,
YearGroups =
from o in c.Orders
group o by o.OrderDate.Year into yg
select
new {Year = yg.Key,
MonthGroups =
from o in yg
group o by o.OrderDate.Month into mg
select new { Month = mg.Key, Orders = mg }
}
};
ObjectDumper.Write(customerOrderGroups, 3);
I'm not overly keen on SQL syntax: I think this sort of complex expression
is hard to read. LINQ has a pretty straightforward conversion to method
calls, and for me this consistent set of methods is the important thing
rather than the SQL syntax. e.g. 'group by' maps directly to a call to a
method GroupBy(), so another of Microsoft's LINQ examples is:
public void Linq45() {
string[] anagrams = {from , salt, earn , last ,
near , form };
var orderGroups = anagrams.GroupBy(
w = w.Trim(),
a = a.ToUpper(),
new AnagramEqualityComparer()
);
ObjectDumper.Write(orderGroups, 1);
}
public class AnagramEqualityComparer : IEqualityComparerstring
{
public bool Equals(string x, string y) {
return getCanonicalString(x) == getCanonicalString(y);
}
public int GetHashCode(string obj) {
return getCanonicalString(obj).GetHashCode();
}
private string getCanonicalString(string word) {
char[] wordChars = word.ToCharArray();
Array.Sortchar(wordChars);
return new string(wordChars);
}
}
Python still wins hands down on this example both in verbosity and
readability:
anagrams = [from , salt, earn , last ,
near , form ]
from itertools import groupby
def AnagramKey(w):
return sorted(w.strip().upper())
for k,words in groupby(sorted(anagrams, key=AnagramKey),
key=AnagramKey):
for w in words:
print w.strip().upper()
print ...
EARN
NEAR
...
SALT
LAST
...
FROM
FORM
...
I haven't yet had occasion to use LINQ in anger yet, so I have no idea
whether its an idea to love or to hate. I do think it is good that C# has
effectively sprouted list comprehensions (not to mention anonymous types
and type inferencing) and I expect there may be some aspects worth looking
at for Python but I think they are more likely to lead to itertools
functions than extensions to syntax.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Sep 24, 10:59 pm, Duncan Booth [EMAIL PROTECTED] wrote: Simple LINQ expressions like the one you gave map easily to Python list comprehensions. What Microsoft have done though is provide a consistent implementation which allows you to write complex SQL like expressions which will work identically on databases or most other sequence types. han extensions to syntax. List comprehensions work with any iterable sequence. You can nest them to make more complex statements. You can also use a generator to iterate through a database or an XML document. Here is approximately where linq stops being a marvelous addition to Python. And I can honestly do without the SQL syntax. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Sep 24, 4:59 pm, Duncan Booth [EMAIL PROTECTED] wrote: ... I haven't yet had occasion to use LINQ in anger yet, so I have no idea whether its an idea to love or to hate. I do think it is good that C# has effectively sprouted list comprehensions (not to mention anonymous types and type inferencing) and I expect there may be some aspects worth looking at for Python but I think they are more likely to lead to itertools functions than extensions to syntax. My thoughts exactly when I first looked at it. Hey C# NOW has list comprehensions!!! SWEET!!! As I understand it LINQ is libraries(System.Data.Linq.dll, System.XML.Linq.dll) + syntactic sugar, i wouldn't call that a change to the language. The addition of lambdas and functions as first class objects however, that was indeed a language change, and it was a change for the better that makes LINQ possible, (also makes writing delegates less cumbersome). To someone other than a C# person, these features are not new or revolutionary, it's just C# catching up. Kudos to them for getting there before java. After some more thought on what might conceivably be missing from python that LINQ has, that someone might want is the equivalent of System.XML.Linq.dll, and I can't see any reason why someone couldn't write it with the exception that there doesn't seem to be a definitive XML lib for python, meaning generally regarded as the best. That in my mind would be a prerequisite. But if someone wrote both the XML lib with the LINQ-ish syntax, maybe it would become the definitive XML lib. Again, I personally don't see myself using XML and thus needing that unless my hand was forced by some business requirement that dictated I use XML, I would not use it if I had a choice. The SQL LiNQ-ish though, I think every python ORM has that covered to a degree, and I use that quite a bit. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On 2008-09-24, Bruno Desthuilliers [EMAIL PROTECTED] wrote: hrishy a écrit : (snip) I apologise (I thought Python programmers were smart and they did know what LINQ was) Is there really any relation between being smart and knowing anything about the latest MS fad ? God, I hope not -- or I'd rather be stupid. -- Grant -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Duncan Booth wrote: r0g [EMAIL PROTECTED] wrote: OK so maybe I'm being naive here but it looks to me like this new paradigm's big idea is to use a python + SQL type syntax to access data in random objects. Big whoop. It's not that difficult to write a generators that wraps XML files and databases is it? What am I missing here? Simple LINQ expressions like the one you gave map easily to Python list comprehensions. What Microsoft have done though is provide a consistent implementation which allows you to write complex SQL like expressions which will work identically on databases or most other sequence types. Hmm, that's a nice idea in theory but I don't think it's the python killer Mr/Ms bearophile thinks it is. I can't think of any use cases where this would save me a great deal of time (certainly not enough to offset the relative slowness of working in C#) but supposing they do exist this stuff definitely belongs in a module. Seems to me C# is playing catchup in most ways and this nugget of 'innovation' is just the exception that proves the rule. Roger. -- http://mail.python.org/mailman/listinfo/python-list
Linq to Python
Hi Will LINQ be ported to Python ? regards Hrishy -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
hrishy wrote: Hi Will LINQ be ported to Python ? Take a look at SQLAlchemy or SQLObject for python-based ORM/SQL-abstractions. Apart from that, python is already heavily based on concepts like iterators, filtering. Take a look at itertools. Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Hi Thanks for those links however LINQ seems to be much more then ORM tool it can for example join an XML file with a relational datasource or create a XSD regards Hrishy --- On Tue, 23/9/08, Diez B. Roggisch [EMAIL PROTECTED] wrote: From: Diez B. Roggisch [EMAIL PROTECTED] Subject: Re: Linq to Python To: python-list@python.org Date: Tuesday, 23 September, 2008, 4:06 PM hrishy wrote: Hi Will LINQ be ported to Python ? Take a look at SQLAlchemy or SQLObject for python-based ORM/SQL-abstractions. Apart from that, python is already heavily based on concepts like iterators, filtering. Take a look at itertools. Diez -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Sep 23, 7:48 am, hrishy [EMAIL PROTECTED] wrote: Hi Will LINQ be ported to Python ? regards Hrishy I think this question is more appropriate to ask on an IronPython development list -- LINQ is pretty solidly intertwined with .Net, and so you'll likely want to look at the .Net implementation of Python. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Sep 23, 2:07 pm, Jason Scheirer [EMAIL PROTECTED] wrote: On Sep 23, 7:48 am, hrishy [EMAIL PROTECTED] wrote: Hi Will LINQ be ported to Python ? regards Hrishy I think this question is more appropriate to ask on an IronPython development list -- LINQ is pretty solidly intertwined with .Net, and so you'll likely want to look at the .Net implementation of Python. But surely the idea behind it will eventually spread. It's really just comprehensions generalized over XML and relational datasets, a noble goal. Besides, it's main purpose for .NET was to bring functional programming to it. Python already has that, somewhat... -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
But surely the idea behind it will eventually spread. It's really just comprehensions generalized over XML and relational datasets, a noble goal. Besides, it's main purpose for .NET was to bring functional programming to it. Python already has that, somewhat... it's really any object out of the box, i think the sql linq stuff is more of a query compiler, IMO sqlalchemy does that. query = select(user_cols, and_(table_relationship.c.accept_user_id==user.id, table_relationship.c.start_date==None ), from_obj=join( table_relationship,table_user, onclause=table_user.c.id==table_relationship.c.init_user_id ).outerjoin(table_profile) ) session.execute(query).fetchall() XML? meh hopefully I would never need it. :) C# is my day job, and when I got my hands on LINQ back in January my initial thought was Finally I have list comprehensions day job is fun again For the most part, I think C# is catching up. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
On Sep 23, 4:48 pm, hrishy [EMAIL PROTECTED] wrote: Will LINQ be ported to Python ? No, because Python already has list comprehensions and we don't need the XML buzzword. -- http://mail.python.org/mailman/listinfo/python-list
Re: Linq to Python
Will LINQ be ported to Python ? I have three suggestions: 1. When starting a new thread, start a *new* thread. Don't tack a new, unrelated subject onto an existing thread. Your post will not be seen by people with readers that collapse thread and who do not happen to read the 'Python is slow?' thread. 2. Also, give enough informaton that people can understand your question without searching the web and guessing. In particular, that do *you* mean by LINQ? The game? The .NET component? Or something else? 3. Before posting, search the Python manuals or the web a bit for an answer. If you mean the .NET component, googling 'Python LINQ' should partly answer your question. tjr -- http://mail.python.org/mailman/listinfo/python-list
