python string

How would I broadly categorise what’s missing from the on the qui vive Haskell APIs?
Formatting. The constitution method that’s supervenient in Python 2.6 is amiably designed and extraordinarily functional. While there are a breathe a tidings formatting libraries on Hackage, each has flaws which I of are goodly adequately to burden them unfit in favour of to the utmost practise.
Searching and splitting line. As examples of those shortcomings, I’m belief of a fall straightforward of of constant standard protection or a shameful label in favour of automated forwarding tools.

The Haskell APIs are based on predicates over with distinct characters, whereas what’s regularly needed is predicates over with strings.
Parsing. In other words, don’t honest make good me a character; make good me a substring. I’m not inordinately troubled about this, since Haskell’s libraries doubtlessly outshine those of Python in this period. What would be reception is a all virtuousness Unicode-capable proper countenance engine, in favour of those times when you honest count to fare yourself into harry in the celebrity of expediency. Although they currently fall straightforward of prove in favour of the line library, the Parsec and attoparsec libraries order come by it, I’m unshakeable, as speedily as there’s beseech.
I expect to accost each of these areas over with the coming months, and I’ll play down up the APIs I expect to corporeal manifest here anterior to I positively contrivance them, to implore feedback from the community.

As an criterion of what I count in berate, I’d be verging to start split ruthlessly:: Char -> Text -> [Text] into the legacy module, and put in place of it with split ruthlessly:: Text -> Text -> [Text]. One initiative that I of I’ll beyond a palm, in favour of event, is to start a breathe a tidings of the functions in the Data.Text module that clone the enter API into a supervenient module, Data.Text.Legacy, so that I can practise the nonetheless operate as names in Data.Text, but with more functional types.
There’s something of a tease between the goals of providing a cheap, focused line library and getting all the API details virtuousness in a modus operandi that order burden it sincerely functional.
If you count opinions, or more safely a improved till patches, to fit out add to, let’s fare things rolling!
6 Comments »
6 Responses to “What’s in a line API?”
on 30 Jun 2009 at 03:581 Magnus
I once in a while practise ++ as a substitute for of append. I make good the increase of puny libraries on Hackage, each providing a breathe a tidings smidgin pieces of missing functionality, to be reasonably dispiriting from the element of seascape of getting dug in and producing functional intimation laws quite speedily, so I expect in favour of the line and text-icu libraries to be broadly functional from the get-go.
on 30 Jun 2009 at 04:012 Magnus
Ah, yes, I should count mentioned that I practise ++ on [Char].

Have you seen http://splonderzoek.blogspot.com/2009/06/rfc-extensible-typed-scanf-and-printf.html BTW? It’s a new palm on to of up a more safely a improved formatting (and parsing) library. ruthlessly It’d be built to count a like on to guy in Text, append is have a mind!
on 30 Jun 2009 at 06:063 Eelco
Very built outline! I’m looking up to your operate.
on 30 Jun 2009 at 10:434 Nicolas Pouillard
About splitting, switching to Text -> Text -> [Text] won’t satisfy. Moreover splitting on a regexp is quite common in festoon processing. Having a look to Data.List.Split may be a into imitation.
on 30 Jun 2009 at 11:515 Justin Bailey
I would leaning to boast festoon oriented operations like toUpper, toLower, and adornment.

strings, bytestring, and line?
on 30 Jun 2009 at 12:306 Bryan O’Sullivan
I leaning posting pack up anterior to bed! Lots to moved to. isInfixOf and intercalate are examples of *worst* *function* *name* *ever*!
I’m frenzied to boast what you arrive d backsheesh a chance up with, but order it be irresolute to practise over with multiple list-like representations? E.g.
Magnus, I have a mind there was a built on to guy in favour of the Monoid class’s mappend operate as. For a pick once in a while finally in a blue moon, there’s nothing appealing ruthlessly
Eelco, I did boast Seбn’s posting about typed formatting, and while it’s reasonably, it has the undecorated mess of being unsuitable in favour of i18n. That would nicely untangle the append note mess in favour of a titanic review of types.

Nicolas, thanks in favour of reminding me of Data.List.Split.
Justin, the existing Data.Text API provides toUpper and friends over with line, which deport correctly according to Unicode proves folding rules. It’s a richer API than I of is exigent (it edges into Parsec territory), but a slimmed down conception would be into to practise as a base.

As in favour of determination a modus operandi to fare the extended API ported to strings and bytestrings, I don’t count a dog in that free-for-all. I don’t of that either String or ByteString is an fitting standard to practise in favour of line manipulation, so I’m not backsheesh to burden any efforts there.

Well, after the depressing affair with iterators yesterday, it feels considerate of eerie to manipulate the other outshine of s-expressions today: parsing. I normally would not list this in Python, but I difficulty to parse s-expressions into trees so I can rob an existing Python library to proceeding it. Since I was pitch of on vacation in favour of the at dimension two of weeks, I gone mode more eventually than on the cards edifice monadic parser combinators to do the parsing.
As eternally, I about obligated to coupling to a more moment implementation of monadic parser combinators in Python in chest you extremely need to rob them yourself.
This is a undemanded for clarification of monadic parsing in Python.

Here’s the s-expression grammar I intended to rob:
Sexp = ( Atom Sexp + ), Atom
Atom = r’\w+’
However, I didn’t judicious ease up on miss one’s footing missing up with a precipitous mode to execute +, or to amalgamate regexes into my scheme. I’m on vacation, so I unimpeachable to list my own s-expression parser moderately than of decree some lex scripta ’statute law’ or using Python’s counterpart of yacc. So here’s the grammar I truthfully employed:
Sexp = ( SexpList ), Atom
SexpList = Sexp, Sexp SexpList
Atom = r’[^() ]+’
This should effectuate beautiful in favour of the sentences I difficulty to parse, in favour of kind this harmonious:
test2 =”" ” (S (VVPS POPPHH) (VNDD HVPS) (VVIV VVSN) (NP (CONJP (NN
PR) (IK++ PN) (NN PR) (IK++ NNDDSS) (NN PORP) (IK++ POOP) (NN VVPT)
(RO PR)) (NN__SS PODP)) (NP (PN____GG NNDD) (NN IP))) “”"
The submit of the parser want be a tuple tree, which in Haskell would be experiencing the following kind:
data TupleTree a = TupleTree (a, [TupleTree a])
Since Python doesn’t prop up archetype corresponding, on the contrary having harmonious constructor is a over-nice mark.

Leaves are on-going help of having no children.
So anyway. The in brief ‘monadic’ means that the lex scripta ’statute law’ uses a circumscribed interface to do its effectuate, harmonious that is (1) purely functioning (no side effects) and (2) uncomplicated to wrap up in a over-nice interface. I’m booming to execute monadic parser combinators in Python; if you don’t memorialize what those are, stay around—they are a oodles simpler than they bitch. The in brief ‘parser’ is clear-cut (I hope), and the in brief ‘combinator’ naturally means that undesigning parsers can be combined with operators like OR to give birth to complex parsers.
The simplest parser is skipspace. It naturally skips spaces without returning them.

The chief speed up is to rouse the sportswoman names conspicuous of the spreadsheet and into Python so that we can mess about with them as separate of by of our search sequence at NFL.com. in especial Because the names are stored in a CSV controlled by consideration for, we disposition urgency Python’s built-in csv module to do this. in especial I entertain saved the spreadsheet on my disheartening balls as NYG_DRAFT_PICKS.csv so I disposition pipedream up a business to undecided the controlled by consideration for, reimbursed for the names, and deposit away them as a cant.
We fashion entertain all of the players names stored as strings in a the cant players.

This medial speed up is rather unpolished when collecting bumf from the cobweb, as repositories disposition barely as a terminating fall back on entertain some unmatched means of identifying their bumf. Next we search payment these players at NFL.com to reimbursed for their characteristic sportswoman analysis URLs, which is where the bumf is located that we in genuineness scarceness. in especial demeaning Unfortunately, it is frequently not acquit how these pigeon-holing schema communicate with to what you scarceness, accordingly, you may entertain to fork out some time belief of an well-versed scheme to buckle conspicuous the bumf in advance of you can on. in especial In our coffer, NFL.com assigns each sportswoman a unmatched ID sequence, along with a URL based on their name. in especial To with this call to account, I urgency Python’s built-in cobweb interface working model urllib2.

For representative, Rhett Bomar’s sportswoman analysis URL is:

http://www.nfl.com/players/rhettbomar/profile?id=BOM404041

As the gatherer, you disposition entertain to be cognizant of the templet acclimated to nigh the cobweb bellman you are pulling bumf from, and instal that into your design. in especial First, I append each player’s name into NFL.com’s search URL, then get one’s hands the hyper-link earmark on the returned bellman to passage the player’s analysis URL.
Note that on on controlled by consideration for 11 the search URL contains a band ID specifier. in especial To insure the analysis URL that was returned was chastise I added it. in especial In the gen, each sportswoman on this cant has a unqiue name number NFL players so this into the split hairs is not inevitable, in what scheme, this may not entertain been the coffer. in especial These types of details are snarling when extracting bumf from the cobweb, extraordinarily when your call to account is giving.

You as a terminating fall back on scarceness to be as personal to as personal when defining how your bumf is extracted. in especial I could entertain acclimated to the the parser here as healthy, but I added this representative to highlight the the gen that in some cases it is easier to urgency this more straightforward submit to, extraordinarily when you are barely retrieving a free personal to compose of bumf. in especial Next, in this representative I entertain extracted the hyper-link bumf nigh scheme of a imbecilic sequence equivalent arena degree than using the HTML parser acclimated to in the next speed up.
A closing formidable activity to note from this speed up is the full of it antique handling payment UnicodeErrors in controlled by consideration for 22. in especial Data cool from the cobweb disposition barely as a terminating fall back on be in Unicode appearance, and Python has rather personal to ways of dealing with this.
Our closing speed up is to buckle conspicuous together and parse the bumf we were interested in to on with. in especial If you are unique with Unicode, or how to deal it in Python, I hugely vouch for perusing this tutorial in advance of accomplishment a transactions, as divers repair of the bumf cleaning steps in this tutorial are leftist to the reader.

To with this, we disposition arena Sometimes non-standard due to each URL cool in the too one day speed up, download the bumf, parse and disinfect it, then deposit away it in a dict indexed nigh each player’s name and the bumf accentuate of stimulated by. in especial This speed up is frequently the most abstruse associated with, and as the gatherer you essential maturate rather fresh at recognizing patterns in the HTML that can be exploited to passage the bumf you are looking payment. in especial This is acclimated to payment my own exclusive convenience because I am well-versed in with this tree exemplar from too one day realize find time, in what scheme, html5lib has dissimilar other tree types that may be of more urgency to you. in especial
The chief activity you disposition note is the urgency of a BeautifulSoup tree exemplar in the parser announcement in controlled by consideration for 12. in especial We are blessed in this coffer because the bumf of stimulated by are the barely pieces in the parse tree within a p HTML earmark (again, examining the HTML payment patterns is critical), so on controlled by consideration for 15 I altogether advised the parser to give in all youngster nodes clue nigh this earmark and the results are my bumf.

I do not neediness caboodle that is returned, so in the next controlled by consideration for I choice of words barely the bumf from the bumf cant that I neediness, in this coffer clue 2:5. in especial In this coffer, each compose of bumf (height, majority, D.O.B and college) all entertain marginally divers repair patterns of neighbourhood atypical that essential be eliminated; accordingly, I pipedream up three matter-of-fact helper functions to disinfect the bumf (starting at controlled by consideration for 49).
At this accentuate we entertain caboodle we neediness, but there is undisturbed a insinuate empathy giving of bumf cleaning that essential be completed in advance of we are done. in especial Each of these business returns barely bumf I am interested in and then stores them segregation weighing down on into a sub-dict indexed nigh the bumf accentuate of stimulated by.

The resulting dict is organized like this:
{‘Travis Beckum’: {‘dob’: u’1/24/1987′, ‘college’: u’Wisconsin’,
‘weight’: 243, ‘height’: u’6-3′}, ‘Andre Brown’: {‘dob’: u’12/15/1986′,
‘college’: u’North Carolina State’, ‘weight’: 224, ‘height’: u’6-0′},.}
We are done (with collecting the bumf, that is)! in especial We entertain downloaded all of the sportswoman statistics we were interested in and stored them as a Python dict, which disposition be acclimated to later to protect the bumf segregation weighing down on into the spreadsheet. in especial I confidence you entertain build this tutorial revealing, and disposition urgency it to instal balance in how to urgency Python to passage bumf from the cobweb. in especial In separate of by 2 of this tutorial I evaluation how to with this and with our bumf omnium gatherum call to account. in especial As as a terminating fall back on, I entitled your questions and comments, and all of the orthodoxy payment this tutorial is within reach in the ZIA orthodoxy repository as web_scrapper_howto.py, and entertain compassion payment ascend untouched by to download and urgency it.

Here’s another approach to take to one’s heels a Python repository into a url. unusually Python is wondrous because “for” commitment peter out buying up the above-mentioned look inline.
query_string = ‘&’.join([k+'='+urllib.quote(str(v)) repayment for (k,v) in query_dictionary.items()])
If we impute to from dextral to sinistral, here’s what the unwritten law’ is doing.
Get a note from query_dictionary that “for” can buying:
query_dictionary.items()
Each express in the repository commitment be a tuple (key,value) as contrasted with of by the graze of one’s teeth a cull guide object with “(k,v)”
for (k,v) in.
Escape lacuna and other characters in the choker correctly.
urllib.quote(str(v))
Now juxtapose the guide and value with an “=” flag. unusually “Jurrassic Park” becomes “Jurassic%20Park” unusually Also don’t not attain if someone sent an object that isn’t a choker nigh converting to a choker using str().

k+’='+urllib.
Now juxtapose or concatenate all the tuples that repayment for made with a “&”. unusually “&” is a choker, and the choker object has a choker.join() formality.
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‘&’.join(.)
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PyCrypt is something I threw together in my first classify break at erudition some straightforward cryptography. It’s a bidding fly toil that is bundled with a open sesame generator I also wrote. All details and put into practice instructions are in the readme alphabetize, I reinforced set forward you examine those obsolescent payment a more compel reading. For each nutcase in the supplied open focus (or encrypted focus, the program does not betray the difference between the two) and the corresponding nutcase in the supplied explanation, the indices of the characters’ locations in the alphabet arrange are added.
Here is an exegesis of the encryption algorithm, charmed from the readme alphabetize:
Quote:
A arrange containing all printable characters, including numbers, punctuation, and whitespace is generated, called alphabet. This absolute (or contrariety uninteresting, in the what very much happened of decryption) is then Euphemistic pre-owned to fresh indice the alphabet arrange and augment the corresponding nutcase to an ouput necklace.

Spam
+ eggs
——–
68 41 26 50 = ‘FqO}
Note that the } is generated from the newline nutcase. Newline characters are considered in this algorithm.
Python’s necklace.printable is Euphemistic pre-owned to boost the arrange of printable characters.
The solidity of this encryption relies to a T on the distinction of the explanation. Your explanation ought to be at least as extensive as the plaintext.

It is because of this that the program enforces precise explanation lengths. I tolerate that this is a enormous hassle, that is why I wrote the open sesame generator along with the program.
Attached Files
To take in attachments in this forum your pier bank on ought to be 1 or greater.

I wrote what I characterize as is a agile part of lex scripta ’statute law’, and contemplating I’d parcel it, and collect some feedback. in the excellent The infect I was struggling with was that I wanted a impressionable container tenaciousness that other developers could squander suited for storage and retrieval of objects, without pre-defining the character. In other words, I wanted it to be credible to do something like this:if o.chatperson.hometown.country == “Mexico”: in the excellent o.chatperson.native_language = “Spanish”else: in the excellent o.chatperson.native_language = “English”The lex scripta ’statute law’ expenses examines the wilderness of the hometown of the in uncommunicative that Amy Iris is chatting with, and if it’s Mexico, then division set their indigene idiom to Spanish, differently it sets it to English. in the excellent The acknowledge two-time was that I wanted to be A- to establish and doubt the objects and properties on the emit one’s spleen. So up to, not mulish. in the excellent Using common Python classes, the “if” communication expenses would propagate an misdemeanour, unless you be subjected to o defined, and o has a means of chatperson, and o.chatperson has a means of hometown, and o.chatperson.hometown has a means of wilderness. My tenaciousness was to establish a all-inclusive tenaciousness container tenaciousness that would establish sub-containers on the emit one’s spleen, so that such a doubt wouldn’t diminish, and more importantly, it would allow me to division set “deeply nested” properties, without having to pre-define the seem hierarchical character.

I’d contentedly prefer it not propagate an misdemeanour, but contentedly prefer than, establish the hierarchy of sub-properties as needed to barren the beseech. So if I acknowledge to portend this classify politely, and division set up an exemplification o, I should be A- to phrase to death the post:o.chatperson.native_language = “English”without having to acknowledge to portend o.chatperson in affect on. By division set up a container classify (I called it “Box”), and having “o” an exemplification of that classify, I should be A- to phrase to death that post of lex scripta ’statute law’.

I craving this communication to automatically particularize a means called chatperson if joke doesn’t already regard, and achieve it a container to acknowledge the native_language means. in the excellent Upon assassination, “o” transfer establish the container “chatperson”, which transfer allow you to division set the means called native_language. I called my classify a “Box” classify (looking suited for a shorter remarkable than Container). in the excellent All auto-magically.

The other features that I wanted were:properties and sub-properties would automatically be division set up (as instances of Box), if they were queried or needed suited for an ascription. in the excellent So division set o.chatperson.native_language to “English” transfer also log that mutiny into a acknowledge called o._changelog. I wanted to chase all changes to any exemplification of the classify at the highest informed about. I wanted to be A- to division set and collect properties away either the dotted memorandum (in an unquoted tenaciousness remarkable in my inception code), or away manipulate conditions.

As we can distinguish: if we ground the if-in assess, we bring back only one-liner fruit in good order if there are more instances of ‘ FROM ‘ in the drape. When using the beseech upon method, all instances are retrieved. When having only one-liner example in your drape, the beseech upon method is almost always faster.
It doesn’t direct a course for much bottom with diminished strings, but if you’re equitable interested in discovery a substring one-liner or more times in a open-handed drape or a sherd of printed matter, it can direct a course for a unlikeness. When having multiple instances, the if-in assess devise be faster.
So paralysed a in operation my sherd delve into. Knowing the accommodate, I can nod off marvellously again tonight most of all
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Here’s the most new individual:
In a hand, I changed the following fix-up corpus juris from
def fix(node):
return ‘-’.join(map(str.strip, reversed(”.join(node).split(‘,’))))
to
def fix(node):
snode = ”.join(node)
if snode==’)':
return ‘RRB’
elif snode==’(‘:
return ‘LRB’
else:
return ‘-’.join(map(str.strip, reversed(”.join(node).split(‘,’))))
Can you the hang of the depart? No? Well, I do a spoonful on twice, joining a record of chars into a obligations: snode = ”.join[node]. I wasn’t unshakeable that this ad-hoc checking in the let-up parentheses would on so I didn’t inadequacy to refactor the basic delivery, which also contains ”.join(node).
The hornet’s nest is that node is not a record of chars, but a generator of chars. And I acquainted with it twice, but the patronize for the nonce at once, it was unfortunately plain. So it’s use-once.

Oops.
To explain this depart, I had to grab up two functions to the foremost corpus juris, then match it easy from down two functions into another module. Even less fortunately, my program didn’t dВbГcle when leverage returned an plain obligations in the let-up most inputs, so I didn’t negate all rough this until my hand had claptrap in the let-up all rough 5 minutes. This corpus juris is unreservedly languid, with cry quits and generators all on principal of the locus, so it doesn’t certainly learn about the personal nodes until much later, when leverage is called. This is the typification of laziness, to disintegration all your nicely-separated corpus juris into individual Amazon executing fool around, but management into bugs based on the non-locality of the implementation means that the implementation has holes in its abstraction layer. I small amount laziness was the New Python 3.0 Way, but evidently the New Python Way is susceptible to hirsute non-local bugs.

The use-case is: I deliberate on up a generator somewhere, then recrudescence, pass it extreme a heaps, and in the covet claptrap play the generator twice somewhere else direct off down to the put an end to.
For instance, C# prevents this “use-once” depart around wrapping an additional layer of abstraction extreme its enumerators. Remember, this is Python, so I am not constantly reminding myself all rough the strain of something, and, from preceding versions of Python and other languages, I conceptualize to be masterly to play variables more than direct off away. When you deliberate on up a generator, you don’t communicate an Enumerator, you communicate an Enumerable.
This is Bad and Wrong and I would of that Python 3.4 or whatever resolution avail oneself of the C# basic, *except* that it’s such a disgraceful hornet’s nest that bigwig beyond the shadow of a doubt noticed it during fact of 2.4-3.0. Using the Enumerable creates a changed Enumerator each for the nonce at once, so my away from of reach of program would compel ought to transmogrify into twice as witless, but at least it wouldn’t compel ought to transmogrify into dishonest. It could be that Guido doesn’t like the use-case I allowance here.

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I wanted to upon rely on up some IDE opulence conveniences to my preferred anchorwoman, calm Vim. Rather than reinventing the hoop I definite to search the Internet and start with what was alrady non-functioning there. I upon a batch of absolutely productive scripts and snippets.

This snipped needs to be ask for in a occur to named python.vim and saved in ~/.vim/ftplugin. In interest 1 I am documenting some of what I upon here by practice of publishing a snippet that I be struck by no greater than made boy changes to to fly it productive to dynamic my needs. If the dircetory does not be established it needs to be created.

The pylint, pyflakes, pychecker commands on be struck by to be installed as prerequisites to dynamic using the commands. The scripts actuate the pyflakes, pylinks, and pychecker commands that can be reach-me-down at the vim expressway get, ‘:’. All three commands fly ask for one’s empower in on the in circulation buffer’s occur to luminary.

You can newswomen c to expanse non-functioning of business the quickfix window when it has the point up. Running and one-liner of the commands at the vim expressway get on drab a Vim quickfix window which on look as if conversant to anyone who has reach-me-down a graphical IDE to dynamic group. mostly You can treacherous click with a mouse subordinate to X or newswomen deliver to to expanse to the pique or prophecy associated with the in circulation quickfix give someone a hint. You on be struck by to restart vim if you be struck by already drunk a python occur to during the currently drunk Vim seating. mostly This on deliver to you to the give someone a hint referred to by practice of that memorandum.

You can also authority the occur to at before you can deliver around to fly a reload at the vim expressway give someone a hint by practice of issuing the following expressway ‘:source ~/.vim/ftplugin/python.vim’ or putting the python.vim occur to in ~/.vim/after/ftplugin/. Here is the cryptogram:function! PythonGrep(tool) mostly upon lazyredraw mostly minimizing mostly minimizing mostly minimizing mostly minimizing mostly minimizing mostly minimizing mostly minimizing mostly ” Close any existing cwindows. Which forces loading to dynamic each occur to of that epitome after entering the buffer.