Re: . is a good idea! (OT, was: Re: do you master list comprehensions?)
I wrote: Kent Johnson wrote: You can do the same thing using a PYTHONSTARTUP file - see http://docs.python.org/tut/node4.html#SECTION00424 You can change the prompts with import sys sys.ps1 = ' ' sys.ps2 = ' ... ' Very cool. I didn't know about this. Does anyone know how to make it work with Pythonwin[1]? Solved my own problem here. For anyone else out there using PythonWin, the solution that worked for me is to put the following (or whatever customizations you want) in a sitecustomize.py somewhere on my PYTHONPATH: import sys sys.ps1 = 'py ' sys.ps2 = '... ' PythonWin (as well as my Command Prompt python) now has the above prompts. Steve -- http://mail.python.org/mailman/listinfo/python-list
Re: . is a good idea! (OT, was: Re: do you master list comprehensions?)
Bengt Richter wrote: Not true on NT4 at least: Alt-Spacebar gets you the system menu paste into the dos window with Alt-spacebar e p Thanks immensely for this -- I love it. --Scott David Daniels [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Thought you might enjoy my super-small flatten function: (though google groups seems to be munging my whitespace today) def flatten(d): flatten([[[1,[2,3],[4,5]],6],[7]])==[1,2,3,4,5,6,7] return reduce(lambda a,b:a+b,[(type(x) in (list, tuple) \ and flatten(x) or [x]) for x in d]) -- http://mail.python.org/mailman/listinfo/python-list
Re: . is a good idea! (OT, was: Re: do you master list comprehensions?)
Keith Dart wrote: Fernando Perez wrote: blatant plug You might want to look at ipython: http://ipython.scipy.org, /blatant plug I did just recently install that. It looks very nice. Would make a great interactive prompt for an IDE, as well. Glad you like it :) And yes, there are plans to clean it up so it can be easily embedded into a full-blown IDE (as well as remaining available for regular command-line use). This keeps on getting delayed by inevitable bug fixes and my very limited time, but it will happen... Best, f -- http://mail.python.org/mailman/listinfo/python-list
Re: . is a good idea! (OT, was: Re: do you master list comprehensions?)
On Fri, 17 Dec 2004 08:03:12 -0500, Kent Johnson [EMAIL PROTECTED] wrote: Steven Bethard wrote: Very cool. I didn't know about this. Does anyone know how to make it work with Pythonwin[1]? (Obviously, I can type the above in manually every time, but I'd much rather have Pythonwin do this automatically for me.) Steve [1] I'd do my example code at the command prompt, but I can't live without copy-paste. ;) You can copy and paste from a Windows command prompt. It's a bit bizarre, but - In the system menu for a command window, pick Properties - On the Options tab, turn on Quick Edit mode - Now you can copy and paste with right-click (!). If you have text selected, right-click will copy, otherwise paste. It's a bit strange but it works. I think it's wonderfully ironic that in Windows - which takes such pains to make everything keyboard accessible - in a *command line* window, which is using keyboard input by its nature - you have to use the mouse for copy and paste!! Not true on NT4 at least: Alt-Spacebar gets you the system menu Follow with e then k which gets you in select mode use arrow keys to move to top left of a box, or whole screen (if there's more buffer than screen, arrows should cause scrolling to access more) hold shift key down and use arrow keys while continuing to hold the shift key down to select a box of text (need not be at edges) this can also scroll through buffer as necessary to select more than can be visible at one time. Just keep holding down shift. press enter to capture box of text to clipboard paste as usual with ctrl-v ins some apps, shift-insert in vim (depending), or paste back into the dos window with Alt-spacebar e p Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
. is a good idea! (OT, was: Re: do you master list comprehensions?)
Nick Coghlan schrieb: data = [['foo','bar','baz'],['my','your'],['holy','grail']] result = [] for d in data: . data = [['foo','bar','baz'],['my','your'],['holy','grail']] . from itertools import chain . result = .join(chain(*data)) 'foobarbazmyyourholygrail' This is the first time I see that and I totally like the idea of writing . instead of at the beginning of a line. Thank you Dr. Dobb! It's unfortunate for c.l.py that Python uses as the default prompt as it messes up the display on mail/news readers that provide syntax highlighting for quotes. I wish everyone would write examples that way! On the other hand - three levels of quoting are really rare, maybe it would be easier to change that in the mail readers... ... or in Py3k ? Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Nick Coghlan wrote: (FYI, I filed bug report #1085744 on SF about this) And Raymond Hettinger was able to decipher my somewhat incoherent rambling (tip: don't try to write bug reports in the wee hours of the morning) and produce a potentially useful modification to PySequence_Tuple. Anyway, I guess the results I got emphasizes the fact that it's important to measure performance of the actual methods you're using on representative input data, rather than relying on overly simple demonstrators. And, of course, don't be *too* concerned about optimisations until you know you actually have a performance problem. . . Cheers, Nick. -- Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia --- http://boredomandlaziness.skystorm.net -- http://mail.python.org/mailman/listinfo/python-list
Re: . is a good idea! (OT, was: Re: do you master list comprehensions?)
Kent Johnson wrote: Keith Dart wrote: What I do is set Python's sys.ps1 variable to something else. I have a module called interactive that I import implicitly by shell alias: py='python -i -c '\''import interactive'\' Which, among other things, sets the prompt to Python You can do the same thing using a PYTHONSTARTUP file - see http://docs.python.org/tut/node4.html#SECTION00424 You can change the prompts with import sys sys.ps1 = ' ' sys.ps2 = ' ... ' blatant plug You might want to look at ipython: http://ipython.scipy.org, which provides you automatically with these prompts: In [1]: for i in range(2): ...: print i, ...: 0 1 In [2]: 99*2 Out[2]: 198 In [3]: _2+1 Out[3]: 199 As a curiosity, ipython was actually born as a sys.ps1/2 hack, by assigning to these objects whose __repr__ would give numbered prompts with results caching. These days it's a full-blown pure python interpreter, not a $PYTHONSTARTUP customization anymore, but it's an interesting little historical curiosity. Especially if you start going very far with interactive customizations, you might not want to rewrite all of ipython's 15K lines of code :) /blatant plug Cheers, f -- http://mail.python.org/mailman/listinfo/python-list
Re: . is a good idea! (OT, was: Re: do you master list comprehensions?)
Steve Holden wrote: Nick Coghlan wrote: Roel Schroeven wrote: Stefan Behnel wrote: This is the first time I see that and I totally like the idea of writing . instead of at the beginning of a line. Thank you Dr. Dobb! It's unfortunate for c.l.py that Python uses as the default prompt as it messes up the display on mail/news readers that provide syntax highlighting for quotes. I use Thunderbird, and started doing it so I could read my own posts. I did copy it from someone, though (but I can't recall who). The trick can also be useful for web tools that strip leading whitespace. Prepending every line with . is not an ideal solution though... I think it gets tiresome very quickly. Aye, can't argue with that. It does have the virtues of reliability and portability, though :) Cheers, Nick. $ python Python 2.4 (#1, Dec 4 2004, 20:10:33) [GCC 3.3.3 (cygwin special)] on cygwin Type help, copyright, credits or license for more information. import sys sys.ps1 = . ; sys.ps2 = . print \ It isn't that hard It isn't that hard . Would it work, I wonder, with a leading space on the prompt? That might be a valid change to the standard prompt. Let's see This line isn't really quoted three times. What I do is set Python's sys.ps1 variable to something else. I have a module called interactive that I import implicitly by shell alias: py='python -i -c '\''import interactive'\' Which, among other things, sets the prompt to Python 433 $ py Python print This has no leader that screws up email programs. This has no leader that screws up email programs. Python -- \/ \/ (O O) -- oOOo~(_)~oOOo Keith Dart [EMAIL PROTECTED] public key: ID: F3D288E4 -- http://mail.python.org/mailman/listinfo/python-list
Re: . is a good idea! (OT, was: Re: do you master list comprehensions?)
Kent Johnson wrote: You can do the same thing using a PYTHONSTARTUP file - see http://docs.python.org/tut/node4.html#SECTION00424 You can change the prompts with import sys sys.ps1 = ' ' sys.ps2 = ' ... ' Very cool. I didn't know about this. Does anyone know how to make it work with Pythonwin[1]? (Obviously, I can type the above in manually every time, but I'd much rather have Pythonwin do this automatically for me.) Steve [1] I'd do my example code at the command prompt, but I can't live without copy-paste. ;) -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Will Stuyvesant wrote: Here is a question about list comprehensions [lc]. The question is dumb because I can do without [lc]; but I am posing the question because I am curious. This: data = [['foo','bar','baz'],['my','your'],['holy','grail']] result = [] for d in data: ... for w in d: ...result.append(w) print result ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] puts all the words in a list, like I want. There's a way to avoid generating the intermediate list if you don't actually need it (e.g. you want to feed the sequence to another method): . data = [['foo','bar','baz'],['my','your'],['holy','grail']] . from itertools import chain . result = .join(chain(*data)) 'foobarbazmyyourholygrail' Some timing with integers: C:\python -m timeit -s data = [range(x) for x in range(1000)] L= []; map(L.e xtend, data); max(L) 10 loops, best of 3: 78.5 msec per loop C:\python -m timeit -s data = [range(x) for x in range(1000)]; from Tkinter im port _flatten max(_flatten(data)) 10 loops, best of 3: 58.4 msec per loop C:\python -m timeit -s data = [range(x) for x in range(1000)]; from itertools import chain max(chain(*data)) 10 loops, best of 3: 43 msec per loop And with strings: C:\python -m timeit -s data = [map(str, range(x)) for x in range(1000)] L= [ ]; map(L.extend, data); ''.join(L) 10 loops, best of 3: 106 msec per loop C:\python -m timeit -s data = [map(str, range(x)) for x in range(1000)]; from Tkinter import _flatten ''.join(_flatten(data)) 10 loops, best of 3: 85.4 msec per loop C:\python -m timeit -s data = [map(str, range(x)) for x in range(1000)]; from itertools import chain ''.join(chain(*data)) 10 loops, best of 3: 1.2 sec per loop ** OUCH!! C:\python -m timeit -s data = [map(str, range(x)) for x in range(1000)]; from itertools import chain ''.join(list(chain(*data))) 10 loops, best of 3: 107 msec per loop Yikes - looks like chain() really sucks for str.join. However, the addition of the 'list' call makes a big difference. Maybe PySequence_Fast should be called PySequence_SlowAsADeadDingo() in this case ;) (FYI, I filed bug report #1085744 on SF about this) Cheers, Nick. -- Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia --- http://boredomandlaziness.skystorm.net -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Diez B. Roggisch wrote: data = [['foo','bar','baz'],['my','your'],['holy','grail']] [e for l in data for e in l] ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] Okay, I tried this in an interactive Python session and it works as stated. My question is, why? How is the interpreter parsing that list expression that it makes sense? -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Steven Bethard wrote: python -m timeit -s data = [range(10) for _ in range(1000)] sum(data, []) 10 loops, best of 3: 54.2 msec per loop python -m timeit -s data = [range(10) for _ in range(1000)] [w for d in data for w in d] 100 loops, best of 3: 1.75 msec per loop The sum function used in this way (or a loop with a +=) is O(N**2) while the LC is O(N). also: timeit -s data = [range(10) for _ in range(1000)] L = sum(data, []) 10 loops, best of 3: 4.02e+004 usec per loop timeit -s data = [range(10) for _ in range(1000)] L = [w for d in data for w in d] 1000 loops, best of 3: 1.12e+003 usec per loop timeit -s data = [range(10) for _ in range(1000)] L = []; map(L.extend, data) 1000 loops, best of 3: 283 usec per loop timeit -s data = [range(10) for _ in range(1000)]; from Tkinter import _flatten L = _flatten(data) 1000 loops, best of 3: 308 usec per loop (the last one supports arbitrary nestings, the others don't) /F -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Timothy Babytch wrote: Will Stuyvesant wrote: data = [['foo','bar','baz'],['my','your'],['holy','grail']] sum(data, []) ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] The second parameter passed to sum is just to overrride default initial value zero. It's worth keeping in mind that this solution has the same efficiency problems that a loop that =+ strings does: python -m timeit -s data = [range(10) for _ in range(100)] sum(data, []) 1000 loops, best of 3: 530 usec per loop python -m timeit -s data = [range(10) for _ in range(100)] [w for d in data for w in d] 1 loops, best of 3: 151 usec per loop python -m timeit -s data = [range(10) for _ in range(1000)] sum(data, []) 10 loops, best of 3: 54.2 msec per loop python -m timeit -s data = [range(10) for _ in range(1000)] [w for d in data for w in d] 100 loops, best of 3: 1.75 msec per loop The sum function used in this way (or a loop with a +=) is O(N**2) while the LC is O(N). Steve -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
On Tue, 14 Dec 2004 00:41:36 +0100, Max M wrote: Fredrik Lundh wrote: Max M wrote: I tried funnies like [[w for w in L] for L in data], That is absolutely correct. It's not a funnie at all. well, syntactically correct or not, it doesn't do what he want... Doh! *I* might not be used to list comprehensions then... You are right. That example could have been expressed more clearly as: result = data result = data[:] :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Will Stuyvesant wrote: data = [['foo','bar','baz'],['my','your'],['holy','grail']] result = [] for d in data: ... for w in d: ...result.append(w) print result ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] Take advantage of the fact that you can have more than one 'for' in a list comprehension: data = [['foo','bar','baz'],['my','your'],['holy','grail']] [item for item_list in data for item in item_list] ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] Steve -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
data = [['foo','bar','baz'],['my','your'],['holy','grail']] [e for l in data for e in l] ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] -- Regards, Diez B. Roggisch -- http://mail.python.org/mailman/listinfo/python-list
do you master list comprehensions?
Here is a question about list comprehensions [lc]. The question is dumb because I can do without [lc]; but I am posing the question because I am curious. This: data = [['foo','bar','baz'],['my','your'],['holy','grail']] result = [] for d in data: ... for w in d: ...result.append(w) print result ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] puts all the words in a list, like I want. How to do this with [lc] instead of for-loops? I tried funnies like [[w for w in L] for L in data], that is correct syntax, but you'd never guess. I know, silly! No need for [lc]! So there's my question. I am sure a one-liner using [lc] will be very enlightening. Like studying LISP. -- I wish there was a knob on the TV to turn up the intelligence. There's a knob called `brightness', but it doesn't work. -- Gallagher -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Will Stuyvesant wrote: data = [['foo','bar','baz'],['my','your'],['holy','grail']] result = [] for d in data: ... for w in d: ...result.append(w) print result ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] puts all the words in a list, like I want. How to do this with [lc] instead of for-loops? data = [['foo','bar','baz'],['my','your'],['holy','grail']] [w for d in data for w in d] ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] See how the for expressions in the list comprehension exactly match your nested for loops? That's all there is to it. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Fredrik Lundh wrote: Max M wrote: I tried funnies like [[w for w in L] for L in data], That is absolutely correct. It's not a funnie at all. well, syntactically correct or not, it doesn't do what he want... Doh! *I* might not be used to list comprehensions then... You are right. That example could have been expressed more clearly as: result = data ;-) -- hilsen/regards Max M, Denmark http://www.mxm.dk/ IT's Mad Science -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
I guess the simplest way to do it is like this: data = [['foo','bar','baz'],['my','your'],['holy','grail']] result=[w for d in data for w in d] result ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Here is one for arbitrary depth:
def unroll(ary):
unrolled = []
for item in ary:
# add test for your favorite sequence type
if ( type(item) == types.ListType or \
type(item) == types.TupleType \
):
unrolled.extend(unroll(item))
else:
unrolled.append(item)
return unrolled
unroll([[1, 2, 3], ('fred', 'barney', ['wilma', 'betty']), 'dino'])
[1, 2, 3, 'fred', 'barney', 'wilma', 'betty', 'dino']
On Monday 13 December 2004 12:51 pm, Will Stuyvesant wrote:
Here is a question about list comprehensions [lc]. The
question is dumb because I can do without [lc]; but I am
posing the question because I am curious.
This:
data = [['foo','bar','baz'],['my','your'],['holy','grail']]
result = []
for d in data:
... for w in d:
...result.append(w)
print result
['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail']
puts all the words in a list, like I want.
How to do this with [lc] instead of for-loops?
I tried funnies like [[w for w in L] for L in data],
that is correct syntax, but you'd never guess.
I know, silly! No need for [lc]! So there's my
question. I am sure a one-liner using [lc] will be very
enlightening. Like studying LISP.
--
James Stroud, Ph.D.
UCLA-DOE Institute for Genomics and Proteomics
611 Charles E. Young Dr. S.
MBI 205, UCLA 951570
Los Angeles CA 90095-1570
http://www.jamesstroud.com/
--
http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
James Stroud wrote:
Here is one for arbitrary depth:
def unroll(ary):
unrolled = []
for item in ary:
# add test for your favorite sequence type
if ( type(item) == types.ListType or \
type(item) == types.TupleType \
):
unrolled.extend(unroll(item))
else:
unrolled.append(item)
return unrolled
unroll([[1, 2, 3], ('fred', 'barney', ['wilma', 'betty']), 'dino'])
[1, 2, 3, 'fred', 'barney', 'wilma', 'betty', 'dino']
or, shorter:
from Tkinter import _flatten as unroll
(1, 2, 3, 'fred', 'wilma', 'betty', 'dino')
(alright, it returns a tuple, but that can be easily fixed, if necessary)
/F
--
http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
I guess the simplest to do it is like this: data = [['foo','bar','baz'],['my','your'],['holy','grail']] result=[w for d in data for w in d] result ['foo', 'bar', 'baz', 'my', 'your', 'holy', 'grail'] -- http://mail.python.org/mailman/listinfo/python-list
Re: do you master list comprehensions?
Max M wrote: I tried funnies like [[w for w in L] for L in data], that is correct syntax, but you'd never guess. That is absolutely correct. It's not a funnie at all. If you find it odd it's only because you are not used to list comprehensiones. well, syntactically correct or not, it doesn't do what he want... In that case you might be more comfortable with: data = [['foo','bar','baz'],['my','your'],['holy','grail']] result = [] for l in data: result += l how about (slightly evil): result = []; map(result.extend, data) /F -- http://mail.python.org/mailman/listinfo/python-list
