Re: [BangPypers] An interesting beginner post at Stackoverflow
On Wed, Oct 21, 2009 at 12:05 PM, Sidharth Kuruvila
sidharth.kuruv...@gmail.com wrote:
d = {a:Hello}
print d.setdefault(a, blah)
Even though the string blah is not being used an object has to be
created to represent it. Even worse, you could put some complex
expression in there expecting it to evaluate only if the key is
missing.
Oh, alright.
Roshan Mathews
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Re: [BangPypers] An interesting beginner post at Stackoverflow
On Wed, Oct 21, 2009 at 12:05 PM, Sidharth Kuruvila
sidharth.kuruv...@gmail.com wrote:
Hi,
d = {a:Hello}
print d.setdefault(a, blah)
Even though the string blah is not being used an object has to be
created to represent it. Even worse, you could put some complex
expression in there expecting it to evaluate only if the key is
missing.
Your explanation is correct for the case of expressions but not for
string blah.
Literal strings are interned. Python maintains a dict of all literal
strings used in the code and all occurrences get the same object.
id(hello)
600320
id(hello)
600320
But if it is an expression, different object is created every time.
id(he + llo)
600704
id(he + llo)
600768
Anand
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Re: [BangPypers] An interesting beginner post at Stackoverflow
What do you mean when you use the word interned? $ pydoc intern Help on built-in function intern in module __builtin__: intern(...) intern(string) - string ``Intern'' the given string. This enters the string in the (global) table of interned strings whose purpose is to speed up dictionary lookups. Return the string itself or the previously interned string object with the same value. ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] An interesting beginner post at Stackoverflow
On Wed, Oct 21, 2009 at 12:31 PM, Anand Chitipothu anandol...@gmail.com wrote:
``Intern'' the given string. This enters the string in the (global)
table of interned strings whose purpose is to speed up dictionary lookups.
Return the string itself or the previously interned string object with the
same value.
Thanks, I didn't know of that. It could be useful sometime. Anyways,
for the current discussion intern-ing is irrelevant.
id('superman')
30792544
id('superman')
30792544
id('superman')
30792544
id('superman')
30792544
id('superman')
30792544
id('super man')
31955768
id('super man')
31955488
id('super man')
31956768
id('super man')
31955768
id('super man')
31955488
Also, http://mail.python.org/pipermail/tutor/2009-July/070157.html
Roshan Mathews
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Re: [BangPypers] An interesting beginner post at Stackoverflow
Hi,
My bad, that was a bit of laziness on my part. The reason why my
code was silly is not to do with interning though that does happen for
strings. Literals, that is numbers and string literals and a few
others are loaded as constants. So the cost of constructing them in
your code has already been taken care of.
A better example would be something like
d = {a:[1,2,3,4]}
print d.setdefault(a, [])
Interning is an optimization done to speed up the comparison of
strings, by making sure that two string with the same text are
represented by the same object.
Regards,
Sidharth
On Wed, Oct 21, 2009 at 12:31 PM, Anand Chitipothu anandol...@gmail.com wrote:
What do you mean when you use the word interned?
$ pydoc intern
Help on built-in function intern in module __builtin__:
intern(...)
intern(string) - string
``Intern'' the given string. This enters the string in the (global)
table of interned strings whose purpose is to speed up dictionary lookups.
Return the string itself or the previously interned string object with the
same value.
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Re: [BangPypers] An interesting beginner post at Stackoverflow
On a similar note, here's a question I recently asked and obtained good
input about tail recursion optimization.
http://stackoverflow.com/questions/1414581/python-recursive-program-to-prime-factorize-a-number
On Wed, Oct 21, 2009 at 1:14 PM, Sidharth Kuruvila
sidharth.kuruv...@gmail.com wrote:
Hi,
My bad, that was a bit of laziness on my part. The reason why my
code was silly is not to do with interning though that does happen for
strings. Literals, that is numbers and string literals and a few
others are loaded as constants. So the cost of constructing them in
your code has already been taken care of.
A better example would be something like
d = {a:[1,2,3,4]}
print d.setdefault(a, [])
Interning is an optimization done to speed up the comparison of
strings, by making sure that two string with the same text are
represented by the same object.
Regards,
Sidharth
On Wed, Oct 21, 2009 at 12:31 PM, Anand Chitipothu anandol...@gmail.com
wrote:
What do you mean when you use the word interned?
$ pydoc intern
Help on built-in function intern in module __builtin__:
intern(...)
intern(string) - string
``Intern'' the given string. This enters the string in the (global)
table of interned strings whose purpose is to speed up dictionary
lookups.
Return the string itself or the previously interned string object with
the
same value.
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Lakshman
becomingguru.com
lakshmanprasad.com
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[BangPypers] An interesting beginner post at Stackoverflow
http://stackoverflow.com/questions/1597764/is-there-a-better-pythonic-way-to-do-this Someone wrote their *first* Python program asking for a more Pythonic way to do it ... and gets valuable feedback from the community including Alex Martelli. I am now researching on a way to gather top posts (w/ python tag) on Stackoverflow to create something similar to weeklyreddit.appspot.com ... -srid ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
Re: [BangPypers] An interesting beginner post at Stackoverflow
On Wed, Oct 21, 2009 at 8:06 AM, srid sridhar.ra...@gmail.com wrote: http://stackoverflow.com/questions/1597764/is-there-a-better-pythonic-way-to-do-this Nice. Martelli says: (avoid setdefault, that was never a good design and doesn't have good performance either, as well as being pretty murky) Any idea why? I am now researching on a way to gather top posts (w/ python tag) on Stackoverflow to create something similar to weeklyreddit.appspot.com Weekly Reddit is such a cool idea, except I end up checking proggit frequently anyways. Then I guilt out when I get the rss posts on Sunday. :-S Roshan Mathews ___ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
