Re: Minimising stack trace
Op Friday 15 May 2015 21:04 CEST schreef Ned Batchelder: > On Friday, May 15, 2015 at 2:50:12 PM UTC-4, Cecil Westerhof wrote: >> While playing with recursion I get: >> RuntimeError: maximum recursion depth exceeded in comparison >> >> But then I get a very long stack trace. Is there a way to make this >> a lot shorter. Now I 'lose' interesting information because of the >> length of the stack trace. > > There isn't a way to shorten the stack trace. If you are losing > information at the top because of your terminal window, you can > likely increase the number of lines it will keep for you. Well, I am not really losing information, but it happens in a script with some output. One of the things I output is information about how deep I am going. If I then get a stack trace of a 1000 lines that is not very helpful. Especially because except the first and last every message is the same. What would be a lot more helpful would be something like: RuntimeError Traceback (most recent call last) /home/cecil/Python/mathDecebal.py in () 355 for i in range(start, end + 1): 356 factorial_iter = factorial_iterative(i) --> 357 factorial_recur = factorial_recursive(i) 358 factorial_recur_old = factorial_recursive_old(i) 359 factorial_tail = factorial_tail_recursion(i) /home/cecil/Python/mathDecebal.py in factorial_recursive(x, y, z) 51 if x < 2: 52 return y ---> 53 return y if z > x else factorial_recursive(x, z * y, z + 1) 54 55 def factorial_recursive_old(x, y = 1): Last call repeated 153 times /home/cecil/Python/mathDecebal.py in factorial_recursive(x, y, z) 48 49 def factorial_recursive(x, y = 1, z = 1): ---> 50 assert x >= 0 51 if x < 2: 52 return y RuntimeError: maximum recursion depth exceeded in comparison I would find that a lot clearer and I do not think you are losing anything useful. > Another option is to reduce the maximum stack depth, so that it > is exceeded sooner, which produces shorter stack traces: > > import sys; > sys.setrecursionlimit(50) Well that would break my code. I just got the above problem with my math functions. I had it tweaked for testing. But when running the test in ipython3 it goes wrong. It looks like ipython3 has a smaller stack, or puts more on the stack as ipython, python3 and python2. Yes, that is correct. When running: python3 mathDecebal.py there is no problem, but when running: ipython3 mathDecebal.py I get a stack overflow. -- Cecil Westerhof Senior Software Engineer LinkedIn: http://www.linkedin.com/in/cecilwesterhof -- https://mail.python.org/mailman/listinfo/python-list
Re: Building CPython
BartC : > I suppose in many cases an object will have no attributes of its own, > and so it can rapidly bypass the first lookup. Almost all objects have quite many instance attributes. That's what tells objects apart. > I don't understand the need for an object creation (to represent A.B > so that it can call it?) but perhaps such an object can already exist, > prepared ready for use. Note that almost identical semantics could be achieved without a class. Thus, these two constructs are almost identical: class C: def __init__(self, x): self.x = x def square(self): return self.x * self.x def cube(self): return self.x * self.square() ## class O: pass def C(x): o = O() def square(): return x * x def cube(): return x * square() o.square = square o.cube = cube return o IOW, the class is a virtually superfluous concept in Python. Python has gotten it probably without much thought (other languages at the time had it). I comes with advantages and disadvantages: + improves readability + makes objects slightly smaller + makes object instantiation slightly faster - goes against the grain of ducktyping - makes method calls slower - makes method call semantics a bit tricky Marko -- https://mail.python.org/mailman/listinfo/python-list
Re: Building CPython
On Sat, 16 May 2015 06:08 pm, Marko Rauhamaa wrote: > Note that almost identical semantics could be achieved without a class. > Thus, these two constructs are almost identical: [...] > IOW, the class is a virtually superfluous concept in Python. Python has > gotten it probably without much thought (other languages at the time had > it). I comes with advantages and disadvantages: Your example is effectively just a way of using closures instead of a class instance. Almost anything you can do with classes, you can do with closures. The big advantage of classes over closures is that you have an interface to access arbitrary class attributes, while you would need a separate closure for each and every attribute you want access to. For example, here is sketch: class K: def method(self, arg): return self.spam + arg k = K() the_method = k.method # bound method as a closure becomes: def make_closure(instance): # instance is equivalent to self above def method(arg): return instance.spam + arg return method the_method = make_closure(obj) # Some object with a spam field. The big advantage of a closure is that you have much more strict encapsulation. The big disadvantage of a closure is that you have much more strict encapsulation. > + improves readability I wouldn't say that. > + makes objects slightly smaller > > + makes object instantiation slightly faster Are you sure? Have you actually benchmarked this? > - goes against the grain of ducktyping > > - makes method calls slower > > - makes method call semantics a bit tricky A couple more negatives: - no such thing as inheritance; - "is-a" relationship tests don't work; - an unfamiliar idiom for most people; Also, at least with Python's implementation, a couple of mixed blessings: ± closures are closed against modification; ± internals of the closure are strictly private; -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Fastest way to remove the first x characters from a very long string
I have a string that contains 10 million characters. The string is formatted as: "001 : some hexadecimal text ... \n 002 : some hexadecimal text ... \n 003 : some hexadecimal text ... \n ... 010 : some hexadecimal text ... \n 011 : some hexadecimal text ... \n" and I need the string to look like: "some hexadecimal text ... \n some hexadecimal text ... \n some hexadecimal text ... \n ... some hexadecimal text ... \n some hexadecimal text ... \n" I can split the string at the ":" then iterate through the list removing the first 8 characters then convert back to a string. This method works, but it takes too long to execute. Any tricks to remove the first n characters of each line in a string faster? Thanks, Bruce -- https://mail.python.org/mailman/listinfo/python-list
Re: Fastest way to remove the first x characters from a very long string
On Sat, May 16, 2015 at 9:28 AM, wrote: > I have a string that contains 10 million characters. > > The string is formatted as: > > "001 : some hexadecimal text ... \n > 002 : some hexadecimal text ... \n > 003 : some hexadecimal text ... \n > ... > 010 : some hexadecimal text ... \n > 011 : some hexadecimal text ... \n" > > and I need the string to look like: > > "some hexadecimal text ... \n > some hexadecimal text ... \n > some hexadecimal text ... \n > ... > some hexadecimal text ... \n > some hexadecimal text ... \n" > > I can split the string at the ":" then iterate through the list removing the > first 8 characters then convert back to a string. This method works, but it > takes too long to execute. > > Any tricks to remove the first n characters of each line in a string faster? > slicing might be faster than searching for : Do you need to do this all at once? If not, use a generator > Thanks, > Bruce > -- > https://mail.python.org/mailman/listinfo/python-list -- Joel Goldstick http://joelgoldstick.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Fastest way to remove the first x characters from a very long string
On Sat, May 16, 2015 at 11:28 PM, wrote:
> I have a string that contains 10 million characters.
>
> The string is formatted as:
>
> "001 : some hexadecimal text ... \n
> 002 : some hexadecimal text ... \n
> 003 : some hexadecimal text ... \n
> ...
> 010 : some hexadecimal text ... \n
> 011 : some hexadecimal text ... \n"
>
> and I need the string to look like:
>
> "some hexadecimal text ... \n
> some hexadecimal text ... \n
> some hexadecimal text ... \n
> ...
> some hexadecimal text ... \n
> some hexadecimal text ... \n"
>
> I can split the string at the ":" then iterate through the list removing the
> first 8 characters then convert back to a string. This method works, but it
> takes too long to execute.
>
> Any tricks to remove the first n characters of each line in a string faster?
Given that your definition is "each line", what I'd advise is first
splitting the string into lines, then changing each line, and then
rejoining them into a single string.
lines = original_text.split("\n")
new_text = "\n".join(line[8:] for line in lines)
Would that work?
ChrisA
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Re: Building CPython
Steven D'Aprano : > A couple more negatives: > > - no such thing as inheritance; Untrue. My simple Scheme object system (125 lines incl. documentation) supports multiple inheritance without classes. Maybe I should port that to Python... > - "is-a" relationship tests don't work; >From the ducktyping point of view, that is an advantage. The whole Linnaean categorization of objects is unnecessary ontological chaff. How many times have people here had to advise newcomers not to inspect type and instance relations of objects and just call the method? > - an unfamiliar idiom for most people; That's impossible to ascertain objectively. Java and JavaScript programmers (of all people!) routinely deal with closures. Marko -- https://mail.python.org/mailman/listinfo/python-list
Re: Fastest way to remove the first x characters from a very long string
On Saturday, May 16, 2015 at 9:46:17 AM UTC-4, Chris Angelico wrote:
> On Sat, May 16, 2015 at 11:28 PM, wrote:
> > I have a string that contains 10 million characters.
> >
> > The string is formatted as:
> >
> > "001 : some hexadecimal text ... \n
> > 002 : some hexadecimal text ... \n
> > 003 : some hexadecimal text ... \n
> > ...
> > 010 : some hexadecimal text ... \n
> > 011 : some hexadecimal text ... \n"
> >
> > and I need the string to look like:
> >
> > "some hexadecimal text ... \n
> > some hexadecimal text ... \n
> > some hexadecimal text ... \n
> > ...
> > some hexadecimal text ... \n
> > some hexadecimal text ... \n"
> >
> > I can split the string at the ":" then iterate through the list removing
> > the first 8 characters then convert back to a string. This method works,
> > but it takes too long to execute.
> >
> > Any tricks to remove the first n characters of each line in a string faster?
>
> Given that your definition is "each line", what I'd advise is first
> splitting the string into lines, then changing each line, and then
> rejoining them into a single string.
>
> lines = original_text.split("\n")
> new_text = "\n".join(line[8:] for line in lines)
>
> Would that work?
>
> ChrisA
Hi Chris,
I meant to say I can split the string at the \n.
Your approach using .join is what I was looking for.
Thank you,
Bruce
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Re: Minimising stack trace
Op Friday 15 May 2015 20:17 CEST schreef Cecil Westerhof: > While playing with recursion I get: > RuntimeError: maximum recursion depth exceeded in comparison > > But then I get a very long stack trace. Is there a way to make this > a lot shorter. Now I ‘lose’ interesting information because of the > length of the stack trace. I found something. I could use: import sys sys.tracebacklimit = 10 The output is different, but I find it useful enough. -- Cecil Westerhof Senior Software Engineer LinkedIn: http://www.linkedin.com/in/cecilwesterhof -- https://mail.python.org/mailman/listinfo/python-list
EuroPython 2015: Come with your partners
We are happy to announce the official EuroPython Partner Program for EuroPython 2015 in Bilbao: *** EuroPython 2015 Partner Program *** https://ep2015.europython.eu/en/events/partner-program/ There is plenty to see in and around Bilbao. We have worked out a set of interesting tours, together with a local tour company to choose from, for partners and EuroPython attendees alike: * Panoramic tour of Bilbao * Excursion to San Sebastian * Guggenheim Museum * Excursion to La Rioja * Boat tour of Bilbao The tours include travel, lunch and tickets (where needed). We’d like to encourage early sign-up, since seats are limited. Registration deadline is June 20th. Enjoy, -- EuroPython 2015 Team http://ep2015.europython.eu/ http://www.europython-society.org/ -- https://mail.python.org/mailman/listinfo/python-list
Re: Fastest way to remove the first x characters from a very long string
On 2015-05-16, bruceg113...@gmail.com wrote: > I have a string that contains 10 million characters. > > The string is formatted as: > > "001 : some hexadecimal text ... \n > 002 : some hexadecimal text ... \n > 003 : some hexadecimal text ... \n > ... > 010 : some hexadecimal text ... \n > 011 : some hexadecimal text ... \n" > > and I need the string to look like: > > "some hexadecimal text ... \n > some hexadecimal text ... \n > some hexadecimal text ... \n > ... > some hexadecimal text ... \n > some hexadecimal text ... \n" > > I can split the string at the ":" then iterate through the list > removing the first 8 characters then convert back to a string. This > method works, but it takes too long to execute. > > Any tricks to remove the first n characters of each line in a string faster? Well, if the strings are all in a file, I'd probably just use sed: $ sed 's/^//g' file1.txt >file2.txt or $ sed 's/^.*://g' file1.txt >file2.txt -- https://mail.python.org/mailman/listinfo/python-list
Re: Fastest way to remove the first x characters from a very long string
On Saturday, May 16, 2015 at 8:30:02 PM UTC+5:30, Grant Edwards wrote: > On 2015-05-16, bruceg113355 wrote: > > > I have a string that contains 10 million characters. > > > > The string is formatted as: > > > > "001 : some hexadecimal text ... \n > > 002 : some hexadecimal text ... \n > > 003 : some hexadecimal text ... \n > > ... > > 010 : some hexadecimal text ... \n > > 011 : some hexadecimal text ... \n" > > > > and I need the string to look like: > > > > "some hexadecimal text ... \n > > some hexadecimal text ... \n > > some hexadecimal text ... \n > > ... > > some hexadecimal text ... \n > > some hexadecimal text ... \n" > > > > I can split the string at the ":" then iterate through the list > > removing the first 8 characters then convert back to a string. This > > method works, but it takes too long to execute. > > > > Any tricks to remove the first n characters of each line in a string faster? > > Well, if the strings are all in a file, I'd probably just use sed: > > $ sed 's/^//g' file1.txt >file2.txt > > or > > $ sed 's/^.*://g' file1.txt >file2.txt And if they are not in a file you could start by putting them (it) there :-) Seriously... How does your 'string' come into existence? How/when do you get hold of it? -- https://mail.python.org/mailman/listinfo/python-list
Secret code in Ex Machina
http://www.reddit.com/r/movies/comments/365f9b/secret_code_in_ex_machina/ -- https://mail.python.org/mailman/listinfo/python-list
Re: Fastest way to remove the first x characters from a very long string
On Saturday, May 16, 2015 at 10:06:31 AM UTC-4, Stefan Ram wrote:
> bruceg113...@gmail.com writes:
> >Your approach using .join is what I was looking for.
>
> I'd appreciate a report of your measurements.
# Original Approach
# -
ss = ss.split("\n")
ss1 = ""
for sdata in ss:
ss1 = ss1 + (sdata[OFFSET:] + "\n")
# Chris's Approach
#
lines = ss.split("\n")
new_text = "\n".join(line[8:] for line in lines)
Test #1, Number of Characters: 165110
Original Approach: 18ms
Chris's Approach: 1ms
Test #2, Number of Characters: 470763
Original Approach: 593ms
Chris's Approach: 16ms
Test #3, Number of Characters: 944702
Original Approach: 2.824s
Chris's Approach:47ms
Test #4, Number of Characters: 5557394
Original Approach: 122s
Chris's Approach: 394ms
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Re: Fastest way to remove the first x characters from a very long string
On Saturday, May 16, 2015 at 11:13:45 AM UTC-4, Rustom Mody wrote: > On Saturday, May 16, 2015 at 8:30:02 PM UTC+5:30, Grant Edwards wrote: > > On 2015-05-16, bruceg113355 wrote: > > > > > I have a string that contains 10 million characters. > > > > > > The string is formatted as: > > > > > > "001 : some hexadecimal text ... \n > > > 002 : some hexadecimal text ... \n > > > 003 : some hexadecimal text ... \n > > > ... > > > 010 : some hexadecimal text ... \n > > > 011 : some hexadecimal text ... \n" > > > > > > and I need the string to look like: > > > > > > "some hexadecimal text ... \n > > > some hexadecimal text ... \n > > > some hexadecimal text ... \n > > > ... > > > some hexadecimal text ... \n > > > some hexadecimal text ... \n" > > > > > > I can split the string at the ":" then iterate through the list > > > removing the first 8 characters then convert back to a string. This > > > method works, but it takes too long to execute. > > > > > > Any tricks to remove the first n characters of each line in a string > > > faster? > > > > Well, if the strings are all in a file, I'd probably just use sed: > > > > $ sed 's/^//g' file1.txt >file2.txt > > > > or > > > > $ sed 's/^.*://g' file1.txt >file2.txt > > > And if they are not in a file you could start by putting them (it) there :-) > > Seriously... How does your 'string' come into existence? > How/when do you get hold of it? Data is coming from a wxPython TextCtrl widget. The widget is displaying data received on a serial port for a user to analyze. -- https://mail.python.org/mailman/listinfo/python-list
Re: Fastest way to remove the first x characters from a very long string
On Sat, May 16, 2015 at 10:22 AM, wrote:
> # Chris's Approach
> #
> lines = ss.split("\n")
> new_text = "\n".join(line[8:] for line in lines)
Looks like the approach you have may be fast enough already, but I'd
wager the generator expression could be replaced with:
map(operator.itemgetter(slice(8, None)), lines)
for a modest speed-up. On the downside, this is less readable.
Substitute itertools.imap for map if using Python 2.x.
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Re: Fastest way to remove the first x characters from a very long string
On 16-5-2015 18:24, bruceg113...@gmail.com wrote: > Data is coming from a wxPython TextCtrl widget. Hm, there should be a better source of the data before it ends up in the textctrl widget. > The widget is displaying data received on a serial port for a user to analyze. If this is read from a serial port, can't you process the data directly when it arrives? This may give you the chance to simply operate on the line as soon as it arrives from the port, before pasting it all in the textctrl Irmen -- https://mail.python.org/mailman/listinfo/python-list
Re: Fastest way to remove the first x characters from a very long string
On Sun, May 17, 2015 at 2:22 AM, wrote:
> # Original Approach
> # -
> ss = ss.split("\n")
> ss1 = ""
> for sdata in ss:
> ss1 = ss1 + (sdata[OFFSET:] + "\n")
>
>
> # Chris's Approach
> #
> lines = ss.split("\n")
> new_text = "\n".join(line[8:] for line in lines)
Ah, yep. This is exactly what str.join() exists for :) Though do make
sure the results are the same for each - there are two noteworthy
differences between these two. Your version has a customizable OFFSET,
where mine is hard-coded; I'm sure you know how to change that part.
The subtler one is that "\n".join(...) won't put a \n after the final
string - your version ends up adding one more newline. If that's
important to you, you'll have to add one explicitly. (I suspect
probably not, though; ss.split("\n") won't expect a final newline, so
you'll get a blank entry in the list if there is one, and then you'll
end up reinstating the newline when that blank gets joined in.) Just
remember to check correctness before performance, and you should be
safe.
ChrisA
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Re: Fastest way to remove the first x characters from a very long string
On Saturday, May 16, 2015 at 12:59:19 PM UTC-4, Chris Angelico wrote:
> On Sun, May 17, 2015 at 2:22 AM, wrote:
> > # Original Approach
> > # -
> > ss = ss.split("\n")
> > ss1 = ""
> > for sdata in ss:
> > ss1 = ss1 + (sdata[OFFSET:] + "\n")
> >
> >
> > # Chris's Approach
> > #
> > lines = ss.split("\n")
> > new_text = "\n".join(line[8:] for line in lines)
>
> Ah, yep. This is exactly what str.join() exists for :) Though do make
> sure the results are the same for each - there are two noteworthy
> differences between these two. Your version has a customizable OFFSET,
> where mine is hard-coded; I'm sure you know how to change that part.
> The subtler one is that "\n".join(...) won't put a \n after the final
> string - your version ends up adding one more newline. If that's
> important to you, you'll have to add one explicitly. (I suspect
> probably not, though; ss.split("\n") won't expect a final newline, so
> you'll get a blank entry in the list if there is one, and then you'll
> end up reinstating the newline when that blank gets joined in.) Just
> remember to check correctness before performance, and you should be
> safe.
>
> ChrisA
Hi Chris,
Your approach more than meets my requirements.
Data is formatted correctly and performance is simply amazing.
OFFSET and \n are small details.
Thank you again,
Bruce
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Re: Secret code in Ex Machina
From: "Seymore4Head" http://www.reddit.com/r/movies/comments/365f9b/secret_code_in_ex_machina/ LOL - It is like an Easter Egg in a movie. C O O L ! -- Dave Multi-AV Scanning Tool - http://multi-av.thespykiller.co.uk http://www.pctipp.ch/downloads/dl/35905.asp -- https://mail.python.org/mailman/listinfo/python-list
Re: Building CPython
On Sat, 16 May 2015 11:59 pm, Marko Rauhamaa wrote: > Steven D'Aprano : > >> A couple more negatives: >> >> - no such thing as inheritance; > > Untrue. My simple Scheme object system (125 lines incl. documentation) Ah yes, I've seen Javascript code like that too. Each line is thirty thousand characters long... *wink* > supports multiple inheritance without classes. Maybe I should port that > to Python... I'd like to see it, but somehow I don't think that your "Scheme object system" is another name for "closures". We were talking about closures, weren't we? It sounds like you have implemented a form of prototype-based object programming. The question of whether prototype-OOP has inheritance is an interesting one. Clearly prototypes implement something *like* inheritance, but it is based in delegation or copying. Delegation-based cloning is quite close to class-based inheritance, but copying-based cloning is not. My sense is that I prefer to say that prototypes don't have inheritance in the same sense as classes, but they have something that plays the same role as inheritance. But if you want to call it inheritance, I can't really argue. >> - "is-a" relationship tests don't work; > > From the ducktyping point of view, that is an advantage. The whole > Linnaean categorization of objects is unnecessary ontological chaff. How > many times have people here had to advise newcomers not to inspect type > and instance relations of objects and just call the method? Um, is that a trick question? I don't remember the last time. >> - an unfamiliar idiom for most people; > > That's impossible to ascertain objectively. Java and JavaScript > programmers (of all people!) routinely deal with closures. I don't think so. I can't say for Javascript, but for Java, there's a lot of confusion around closures, they've been described as "evil" with the recommendation not to use them, and people cannot even agree when they were introduced! http://java.dzone.com/articles/whats-wrong-java-8-currying-vs www.javaworld.com/javaworld/jw-06-2008/jw-06-closures.html I mean, people had to *debate* the introduction of closures? There were three competing proposals for them, plus an argument for "don't add them". Some people say closures were added in Java 7, others say closures have been there since the beginning, and James Gosling himself says that Java used inner classes instead of closures but the result was painful... It seems to me that in the Java community, there's a lot of confusion over closures, which are seen as an advanced (and rather scary) feature. Hardly routine. -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: Building CPython
Steven D'Aprano :
> On Sat, 16 May 2015 11:59 pm, Marko Rauhamaa wrote:
>> supports multiple inheritance without classes. Maybe I should port that
>> to Python...
>
> I'd like to see it, but somehow I don't think that your "Scheme object
> system" is another name for "closures". We were talking about closures,
> weren't we?
Ok, here's a quick port that have barely tried out:
### Simple OO Framework
class _O: pass
def make_object(*procedures, base=None, bases=None):
o = _O()
methods = {}
setattr(o, '%methods', methods)
if base is not None:
inherit_single(o, base)
elif bases is not None:
inherit_multi(o, bases)
for procedure in procedures:
methods[procedure.__name__] = procedure
setattr(o, procedure.__name__, procedure)
return o
def inherit_single(o, base):
methods = getattr(o, '%methods')
for name, method in getattr(base, '%methods').items():
methods[name] = method
setattr(o, name, method)
def inherit_multi(o, bases):
for base in bases:
inherit_single(o, base)
### Used as follows
def TCPClient():
def connect(socket_address):
...
return make_object(connect)
def SMTPClient():
tcp_client = TCPClient()
def connect(host):
tcp_client.connect((host, 25))
def send_message(message):
...
return make_object(send_message, base=tcp_client)
client = SMTPClient()
client.connect('mail.example.com')
> I mean, people had to *debate* the introduction of closures? There were
> three competing proposals for them, plus an argument for "don't add them".
> Some people say closures were added in Java 7, others say closures have
> been there since the beginning, and James Gosling himself says that Java
> used inner classes instead of closures but the result was painful...
I'm with those who say anonymous and named inner classes have been there
forever and serve the purpose of closures. Yes, Java's boilerplate
requirements are painful, but if you don't like that, use Python.
> It seems to me that in the Java community, there's a lot of confusion over
> closures, which are seen as an advanced (and rather scary) feature. Hardly
> routine.
Importantly, anonymous inner classes have been in active use by Java
newbs from day one.
Marko
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Rule of order for dot operators?
Greetings,
Noobie question regarding a single line of code that transforms a URL
slug ("this-is-a-slug") into a title ("This Is A Slug").
title = slug.replace('-',' ').title()
This line also works if I switched the dot operators around.
title = slug.title().replace('-',' ')
I'm reading the first example as character replacement first and title
capitalization second, and the second example as title capitalization
first and character replacement second.
Does python perform the dot operators from left to right or according to
a rule of order (i.e., multiplication/division before add/subtract)?
Thank you,
Chris Reimer
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Re: Rule of order for dot operators?
On 05/16/2015 12:20 PM, C.D. Reimer wrote:
Greetings,
Noobie question regarding a single line of code that transforms a URL
slug ("this-is-a-slug") into a title ("This Is A Slug").
title = slug.replace('-',' ').title()
This line also works if I switched the dot operators around.
title = slug.title().replace('-',' ')
I'm reading the first example as character replacement first and title
capitalization second, and the second example as title capitalization
first and character replacement second.
Does python perform the dot operators from left to right or according
to a rule of order (i.e., multiplication/division before add/subtract)?
Yes, that's correct.
Gary Herron
Thank you,
Chris Reimer
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Dr. Gary Herron
Department of Computer Science
DigiPen Institute of Technology
(425) 895-4418
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Re: Rule of order for dot operators?
On Sat, May 16, 2015 at 3:20 PM, C.D. Reimer wrote:
> Greetings,
>
> Noobie question regarding a single line of code that transforms a URL slug
> ("this-is-a-slug") into a title ("This Is A Slug").
>
> title = slug.replace('-',' ').title()
>
> This line also works if I switched the dot operators around.
>
> title = slug.title().replace('-',' ')
>
> I'm reading the first example as character replacement first and title
> capitalization second, and the second example as title capitalization first
> and character replacement second.
>
> Does python perform the dot operators from left to right or according to a
> rule of order (i.e., multiplication/division before add/subtract)?
>
> Thank you,
>
> Chris Reimer
> --
> https://mail.python.org/mailman/listinfo/python-list
>From left to right. So in your first example it replaces - with
space, then capitalizes each word.
In your second example, it does the caps first, then gets rid of the dashes
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Joel Goldstick
http://joelgoldstick.com
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Re: Rule of order for dot operators?
C.D. Reimer wrote:
> Greetings,
>
> Noobie question regarding a single line of code that transforms a URL
> slug ("this-is-a-slug") into a title ("This Is A Slug").
>
> title = slug.replace('-',' ').title()
>
> This line also works if I switched the dot operators around.
>
> title = slug.title().replace('-',' ')
>
> I'm reading the first example as character replacement first and title
> capitalization second, and the second example as title capitalization
> first and character replacement second.
>
> Does python perform the dot operators from left to right or according to
> a rule of order (i.e., multiplication/division before add/subtract)?
You can find out yourself by using operations where the order does matter:
"Test".upper().lower()
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Re: Rule of order for dot operators?
C.D. Reimer wrote:
Who?
> Noobie
What?
> question regarding a single line of code that transforms a URL
> slug ("this-is-a-slug") into a title ("This Is A Slug").
>
> title = slug.replace('-',' ').title()
>
> This line also works if I switched the dot operators around.
>
> title = slug.title().replace('-',' ')
>
> I'm reading the first example as character replacement first and title
> capitalization second, and the second example as title capitalization
> first and character replacement second.
You are reading correctly.
> Does python perform the dot operators from left to right or according to
> a rule of order (i.e., multiplication/division before add/subtract)?
Yes. If you debug the code, which you should have done before posting [1] ,
you will see that
'this-is-a-slug'.title() == 'This-Is-A-Slug'
It follows that in this special case it does not matter if you call .title()
before or after .replace().
However, for greater efficiency, in general you should call .replace() in
such a way that the length of the string it operates on is minimized. For
example, if feasible, always slice *before* .replace().
[1]
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Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.
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Re: Rule of order for dot operators?
On 5/16/2015 12:40 PM, Thomas 'PointedEars' Lahn wrote: However, for greater efficiency, in general you should call .replace() in such a way that the length of the string it operates on is minimized. For example, if feasible, always slice *before* .replace(). Slice was how I got the slug from the URL in the first place. :) Thank you, Chris Reimer -- https://mail.python.org/mailman/listinfo/python-list
Re: Rule of order for dot operators?
On 5/16/2015 12:34 PM, Peter Otten wrote: You can find out yourself by using operations where the order does matter: "Test".upper().lower() I was wondering about that and couldn't think of an example off the top of my head. Thank you, Chris Reimer -- https://mail.python.org/mailman/listinfo/python-list
Re: Rule of order for dot operators?
On 2015-05-16 12:20, C.D. Reimer wrote: > Does python perform the dot operators from left to right or > according to a rule of order (i.e., multiplication/division before > add/subtract)? Yes, Python evaluates dot-operators from left to right. -tkc -- https://mail.python.org/mailman/listinfo/python-list
Re: Building CPython
Marko Rauhamaa :
> Ok, here's a quick port that have barely tried out:
And here's a more complete port (with some possible dunder abuse):
### Simple OO Framework
class _O: pass
def make_object(*procedures, base=None, bases=None):
o = _O()
methods = {}
o.__methods__ = methods
o.__derived__ = None
if base is not None:
_inherit_single(o, base)
elif bases is not None:
_inherit_multi(o, bases)
for procedure in procedures:
methods[procedure.__name__] = procedure
def method(*args, __procedure__=procedure, __dispatch__=True, **kwargs):
if not __dispatch__ or o.__derived__ is None:
return __procedure__(*args, **kwargs)
derived = o
while derived.__derived__ is not None:
derived = derived.__derived__
return getattr(derived, __procedure__.__name__)(*args, **kwargs)
setattr(o, procedure.__name__, method)
return o
def _inherit_single(o, base):
methods = o.__methods__
for name, method in base.__methods__.items():
methods[name] = method
setattr(o, name, method)
def _inherit_multi(o, bases):
for base in bases:
_inherit_single(o, base)
def delegate(method, *args, **kwargs):
return method(*args, __dispatch__=False, **kwargs)
### Used as follows
def TCPClient():
def connect(address):
pass
def shut_down():
pass
return make_object(connect, shut_down)
def SMTPClient():
tcp_client = TCPClient()
def connect(address):
delegate(tcp_client.connect, address)
do_stuff()
def send_message(message):
pass
return make_object(connect, send_message, base=tcp_client)
client = SMTPClient()
client.connect(None)
Marko
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Re: Fastest way to remove the first x characters from a very long string
On 16May2015 10:35, bruceg113...@gmail.com wrote:
On Saturday, May 16, 2015 at 12:59:19 PM UTC-4, Chris Angelico wrote:
On Sun, May 17, 2015 at 2:22 AM, wrote:
> # Original Approach
> # -
> ss = ss.split("\n")
> ss1 = ""
> for sdata in ss:
> ss1 = ss1 + (sdata[OFFSET:] + "\n")
>
> # Chris's Approach
> #
> lines = ss.split("\n")
> new_text = "\n".join(line[8:] for line in lines)
[...]
Your approach more than meets my requirements.
Data is formatted correctly and performance is simply amazing.
OFFSET and \n are small details.
The only comment I'd make at this point is to consider if you really need a
single string at the end. Keeping it as a list of lines may be more flexible.
(It will consume more memory.) If you're doing more stuff with the string as
lines then you'd need to re-split it, and so forth.
Cheers,
Cameron Simpson
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Re: Fastest way to remove the first x characters from a very long string
On Sat, 16 May 2015 06:28:19 -0700, bruceg113355 wrote: > I have a string that contains 10 million characters. > > The string is formatted as: > > "001 : some hexadecimal text ... \n 002 : some hexadecimal text > ... \n 003 : some hexadecimal text ... \n ... > 010 : some hexadecimal text ... \n 011 : some hexadecimal text > ... \n" > > and I need the string to look like: > > "some hexadecimal text ... \n some hexadecimal text ... \n some > hexadecimal text ... \n ... > some hexadecimal text ... \n some hexadecimal text ... \n" Looks to me as if you have a 10 Mbyte encoded file with line numbers as ascii text and you're trying to strip the line numbers before decoding the file. Are you looking for a one-off solution, or do you have a lot of these files? If you have a lot of files to process, you could try using something like sed. sed -i.old 's/^\d+ : //' *.ext -- Denis McMahon, denismfmcma...@gmail.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Rule of order for dot operators?
On Sun, 17 May 2015 05:20 am, C.D. Reimer wrote:
> Greetings,
>
> Noobie question regarding a single line of code that transforms a URL
> slug ("this-is-a-slug") into a title ("This Is A Slug").
>
> title = slug.replace('-',' ').title()
>
> This line also works if I switched the dot operators around.
Technically, dot is not an operator, but even if it was, swapping the *dots*
around makes no difference:
slug.replace('-',' ').title() => slug.replace('-',' ').title()
Because a dot is a dot, right? What you mean is that you're swapping the
*methods* around, not just the dots:
slug.replace('-',' ').title() => slug.title().replace('-',' ')
> title = slug.title().replace('-',' ')
>
> I'm reading the first example as character replacement first and title
> capitalization second, and the second example as title capitalization
> first and character replacement second.
>
> Does python perform the dot operators from left to right or according to
> a rule of order (i.e., multiplication/division before add/subtract)?
Left to right.
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Steven
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Re: Rule of order for dot operators?
On Sun, 17 May 2015 05:40 am, Thomas 'PointedEars' Lahn wrote: > C.D. Reimer wrote: > > Who? Don't be a dick, Thomas. Lots of people use their initials. You use your nickname as part of your sender address, why are you questioning somebody for using their initials? >> Noobie > > What? Where? When? Why? How? I'm pretty sure you've been on the Internet for long enough to know what "noobie", "n00b", "newbie" etc mean. But just in case you need help: http://lmgtfy.com/?q=noobie -- Steven -- https://mail.python.org/mailman/listinfo/python-list
Re: How to deploy a custom common module?
> When I deploy test.py on another computer, I put (rsync) both test.py and > cmn_funcs.py in the same remote directory. > > If I create another python project (test2.py) in new directory, that needs > common functions, what should I do with cmn_funcs.py? I put my shared code in a separate folder, named something like /path/to/module_dir. I then add to /etc/profile.d/something.sh: export PYTHONPATH=$PYTHONPATH:/path/to/module_dir -- https://mail.python.org/mailman/listinfo/python-list
Re: How to deploy a custom common module?
On 17-5-2015 4:06, Jason Friedman wrote: >> When I deploy test.py on another computer, I put (rsync) both test.py and >> cmn_funcs.py in the same remote directory. >> >> If I create another python project (test2.py) in new directory, that needs >> common functions, what should I do with cmn_funcs.py? > > I put my shared code in a separate folder, named something like > /path/to/module_dir. > > I then add to /etc/profile.d/something.sh: > > export PYTHONPATH=$PYTHONPATH:/path/to/module_dir > I think you could use the user site packages directory as well for this... then you should not have to change the PYTHONPATH. https://docs.python.org/3.5/library/site.html#site.USER_SITE (if you don't want to or cannot install into to the system's site-packages directory) Irmen -- https://mail.python.org/mailman/listinfo/python-list
Re: Rule of order for dot operators?
On Sunday, May 17, 2015 at 7:15:13 AM UTC+5:30, Steven D'Aprano wrote: > On Sun, 17 May 2015 05:40 am, Thomas 'PointedEars' Lahn wrote: > > > C.D. Reimer wrote: > > > > Who? > > Don't be a dick, Thomas. Lots of people use their initials. You use your > nickname as part of your sender address, why are you questioning somebody > for using their initials? Not only is it a ridiculous objection, I dont even understand what the objection is. Among the eminent this is quite common Dijkstra -- ewd Stallman -- rms Eric Raymond -- esr And even for non-eminent like your truly, most of my working life most people called me 'rpm' than Rusi/Mody or any such. -- https://mail.python.org/mailman/listinfo/python-list
