Re: [Tutor] How to determine if every character in one string is inanother string?
Alan Gauld wrote: > "Terry Carroll" <[EMAIL PROTECTED]> wrote > >> if Y in X: > > FWIW I believe that 'in' did only work for single characters up until > version 2.X so your ideas may have been based on experiences with > an earlier Python version. Yes, it changed in Python 2.3. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to determine if every character in one string is inanother string?
"Terry Carroll" <[EMAIL PROTECTED]> wrote > if Y in X: > > Which is much more elegant/pythonic; but I didn't know you could do > that > with one string over another. For some reason, I had thought Y > would have > to exactly match one iterable element in X (e.g., one element of a > list, > or one character of a string) for that to work. FWIW I believe that 'in' did only work for single characters up until version 2.X so your ideas may have been based on experiences with an earlier Python version. Alan G. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to determine if every character in one string is inanother string?
On Tue, 24 Jul 2007, wesley chun wrote: > i don't have any time myself either (getting ready for OSCON talk), > but i'm not sure what terry's OP was about... looking for a > well-written piece of code, a faster-performing snippet, or both? i > think he was just unsatissfied with his 1st attempt. Exactly. It worked fine, but just seemed unpythonic to me. To use an analogy, not long ago I thought the best way to see if string X contained string Y was: if X.find(Y) != -1 Which works just fine. But another poster pointed out: if Y in X: Which is much more elegant/pythonic; but I didn't know you could do that with one string over another. For some reason, I had thought Y would have to exactly match one iterable element in X (e.g., one element of a list, or one character of a string) for that to work. Similarly, I was thinking that while that first attempt of mine worked, its apparent-to-me lameness suggested that there was a more idiomatic approach, and I wanted to find out what that was. Seeing the different approaches put forward by the various contributors was pretty interesting, though, I must say. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to determine if every character in one string is inanother string?
> any() and all() also short-circuit, and they move the iteration out of > Python into the C runtime. My guess is the solutions with any() and > all() and equivalent hoisting of string.printable will be faster than > yours, but I don't want to take the time to check ATM...I would also try > using set(string.printable) instead of string.printable... if they do, yeah, that'll be faster since it'll run in C. you're probably also right about set since it doesn't have to "look into a string" to see whether it has a character or not. (this is the same as the advantages that a hash table has over an array.). > Anyone feel like spending some time with timeit? Otherwise we're just > guessing anyway. i don't have any time myself either (getting ready for OSCON talk), but i'm not sure what terry's OP was about... looking for a well-written piece of code, a faster-performing snippet, or both? i think he was just unsatissfied with his 1st attempt. -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Core Python Programming", Prentice Hall, (c)2007,2001 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to determine if every character in one string is inanother string?
wesley chun wrote: > from string import printable as prglobal > def printable(s): > prlocal = prglobal > for x in s: > if x not in prlocal: > return False > return True > > the solutions using LCs above are great when it comes to an expressive > piece of code in a one-liner, but i feel there's a waste of > time/memory. the use of GEs is better, but it still has to iterate > over the entire string when i don't feel that it should be necessary > as per my example. anyway, just my $0.02! not the shortest, but > hopefully the fastest! any() and all() also short-circuit, and they move the iteration out of Python into the C runtime. My guess is the solutions with any() and all() and equivalent hoisting of string.printable will be faster than yours, but I don't want to take the time to check ATM...I would also try using set(string.printable) instead of string.printable... Anyone feel like spending some time with timeit? Otherwise we're just guessing anyway. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to determine if every character in one string is inanother string?
> > > > all(char in string.printable for char in testString) > > That was my favorite, too. I didn't notice the new all method in 2.5. It > certainly seems the most Pythonic approach. all() has a sister built-in function, also introduced in 2.5, so i think that any(char not in string.printable for char in testString) will work too. however, believe it or not, i kinda like your original answer... it's not as lame as you think! :-) i tweaked it slightly (for performance reasons) to: from string import printable as prglobal def printable(s): prlocal = prglobal for x in s: if x not in prlocal: return False return True - i got rid of the list comp and the list comparisons... they're not necessary and slow things down - i moved the import outside the function... not sure why i did this. must be leftover from the days i used to think that the import would occur every time the function's called, but now i know that there's a difference between "importing" and "loading" of a module! - i also created a local reference to string.printable to speed up the lookup -- recall the name resolution order is: locals, globals, built-ins - i also also short-circuit the rest of the string if/when it finds the 1st non-printable. (no need to go on in a 10-million character string if char#2 is a non-printable right?) the solutions using LCs above are great when it comes to an expressive piece of code in a one-liner, but i feel there's a waste of time/memory. the use of GEs is better, but it still has to iterate over the entire string when i don't feel that it should be necessary as per my example. anyway, just my $0.02! not the shortest, but hopefully the fastest! cheers, -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "Core Python Programming", Prentice Hall, (c)2007,2001 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to determine if every character in one string is inanother string?
On Sun, 22 Jul 2007, Jerry Hill wrote: > On 7/21/07, Alan Gauld <[EMAIL PROTECTED]> wrote: > > > all(char in string.printable for char in testString) > > > > What is all? > > Is that a 2.5 thing (I'm still on 2.4 here) > > Yes, it's a 2.5 thing. That was my favorite, too. I didn't notice the new all method in 2.5. It certainly seems the most Pythonic approach. I really enjoyed seeing all the proposed alternatives, however. Thanks, everybody! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to determine if every character in one string is inanother string?
On 7/21/07, Alan Gauld <[EMAIL PROTECTED]> wrote: > > all(char in string.printable for char in testString) > > What is all? > Is that a 2.5 thing (I'm still on 2.4 here) Yes, it's a 2.5 thing. All returns true if all of the elements of an iterable are true. According to the docs, it is the equivalent of the following: def all(iterable): for element in iterable: if not element: return False return True Using 'all' with a generator expression has the virtue of only needing to look at the string until it finds a single element that is false, and then returning. Not only that, it's concise (a single line) and quite readable (at least to me). -- Jerry ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How to determine if every character in one string is inanother string?
"Jerry Hill" <[EMAIL PROTECTED]> wrote > I like this one: > all(char in string.printable for char in testString) What is all? Is that a 2.5 thing (I'm still on 2.4 here) testString = "qwerty\buiop" all(char in string.printable for char in testString) > False > > -- > Jerry > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
