Re: Flatten a list/tuple and Call a function with tuples
On Thu, 26 Jul 2007 00:58:10 +, beginner wrote: I need nested lists to represent nested records in a script. Since the structure of the underlying data is nested, I think it is probably reasonable to represent them as nested lists. For example, if I have the below structure: Big Record Small Record Type A Many Small Record Type B Small Record Type C It is pretty natural to use lists, although after a while it is difficult to figure out the meaning of the fields in the lists. If only there were a way to 'attach' names to members of the list. That's where you may start looking into classes. The simplest one is for just holding attributes seems to be the bunch: In [15]: class Bunch(object): : def __init__(self, **kwargs): : self.__dict__ = kwargs : In [16]: small_a = Bunch(foo=42, bar=23) In [17]: many_b = [1, 2, 3] In [18]: small_c = Bunch(name='eric', profession='viking') In [19]: big_record = Bunch(small_a=small_a, many_b=many_b, small_c=small_c) In [20]: big_record.small_a.bar Out[20]: 23 In [21]: big_record.many_b[1] Out[21]: 2 For the unpacking question, I encountered it when working with list comprehensions. For example: [ f(*x,1,2) for x in list] is difficult to do if I don't want to expand *x to x[0]..x[n]. There are usually 7-10 items in the list and it is very tedious and error prone. If you are the designer of `f` then just receive the whole `x` as *one* argument. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 9:50 am, beginner [EMAIL PROTECTED] wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) Thanks, cg I'm not sure about the first question, but as for the second, you could do a few different things. You could just pass the tuple itself into the function and have the tuple unpacked inside the function. code f(a) def f (tuple): x,y,z = tuple /code You could also pass the elements of the tuple in: f(a[0], a[1], a[2]) That would do it the way you describe in your post. Mike -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Wed, 25 Jul 2007 14:50:18 +, beginner wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. A recursive function, always yielding the first element of the list, could do the job. See the ASPN Python Cookbook for a few implementations. http://aspn.activestate.com/ASPN/search? query=flattensection=PYTHONCKBKtype=Subsection Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) def foo(a, b, c): print a, b, c ... t = (1, 2, 3) foo(*t) 1 2 3 Have a look at the official tutorial, 4.7.4 http://www.python.org/doc/ current/tut/node6.html#SECTION00674 Thanks, cg HTH, Stargaming -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 10:19 am, Stargaming [EMAIL PROTECTED] wrote: On Wed, 25 Jul 2007 14:50:18 +, beginner wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. A recursive function, always yielding the first element of the list, could do the job. See the ASPN Python Cookbook for a few implementations.http://aspn.activestate.com/ASPN/search? query=flattensection=PYTHONCKBKtype=Subsection Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) def foo(a, b, c): print a, b, c ... t = (1, 2, 3) foo(*t) 1 2 3 Have a look at the official tutorial, 4.7.4http://www.python.org/doc/ current/tut/node6.html#SECTION00674 Thanks, cg HTH, Stargaming Hi Stargaming, I know the * operator. However, a 'partial unpack' does not seem to work. def g(): return (1,2) def f(a,b,c): return a+b+c f(*g(),10) will return an error. Do you know how to get that to work? Thanks, cg -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 10:46 am, beginner [EMAIL PROTECTED] wrote: On Jul 25, 10:19 am, Stargaming [EMAIL PROTECTED] wrote: On Wed, 25 Jul 2007 14:50:18 +, beginner wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. A recursive function, always yielding the first element of the list, could do the job. See the ASPN Python Cookbook for a few implementations.http://aspn.activestate.com/ASPN/search? query=flattensection=PYTHONCKBKtype=Subsection Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) def foo(a, b, c): print a, b, c ... t = (1, 2, 3) foo(*t) 1 2 3 Have a look at the official tutorial, 4.7.4http://www.python.org/doc/ current/tut/node6.html#SECTION00674 Thanks, cg HTH, Stargaming Hi Stargaming, I know the * operator. However, a 'partial unpack' does not seem to work. def g(): return (1,2) def f(a,b,c): return a+b+c f(*g(),10) will return an error. Do you know how to get that to work? Thanks, cg As I mentioned, you can access the elements individually using square brackets. The following works: f(g()[0], g()[1], 10) But it's not clear. Unfortunately, I'm not seeing much else for tuple unpacking except the obvious: a,b=g() f(a,b,10) Mike -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 11:00 am, [EMAIL PROTECTED] wrote: On Jul 25, 10:46 am, beginner [EMAIL PROTECTED] wrote: On Jul 25, 10:19 am, Stargaming [EMAIL PROTECTED] wrote: On Wed, 25 Jul 2007 14:50:18 +, beginner wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. A recursive function, always yielding the first element of the list, could do the job. See the ASPN Python Cookbook for a few implementations.http://aspn.activestate.com/ASPN/search? query=flattensection=PYTHONCKBKtype=Subsection Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) def foo(a, b, c): print a, b, c ... t = (1, 2, 3) foo(*t) 1 2 3 Have a look at the official tutorial, 4.7.4http://www.python.org/doc/ current/tut/node6.html#SECTION00674 Thanks, cg HTH, Stargaming Hi Stargaming, I know the * operator. However, a 'partial unpack' does not seem to work. def g(): return (1,2) def f(a,b,c): return a+b+c f(*g(),10) will return an error. Do you know how to get that to work? Thanks, cg As I mentioned, you can access the elements individually using square brackets. The following works: f(g()[0], g()[1], 10) But it's not clear. Unfortunately, I'm not seeing much else for tuple unpacking except the obvious: a,b=g() f(a,b,10) Mike- Hide quoted text - - Show quoted text - Unfortunately f(g()[0], g()[1], 10) is calling g() twice. Sometimes this is not a good idea. a,b=g() f(a,b,10) would work until you want it to be an expression. -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
beginner wrote: On Jul 25, 10:19 am, Stargaming [EMAIL PROTECTED] wrote: On Wed, 25 Jul 2007 14:50:18 +, beginner wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. A recursive function, always yielding the first element of the list, could do the job. See the ASPN Python Cookbook for a few implementations.http://aspn.activestate.com/ASPN/search? query=flattensection=PYTHONCKBKtype=Subsection Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) def foo(a, b, c): print a, b, c ... t = (1, 2, 3) foo(*t) 1 2 3 Have a look at the official tutorial, 4.7.4http://www.python.org/doc/ current/tut/node6.html#SECTION00674 Thanks, cg HTH, Stargaming Hi Stargaming, I know the * operator. However, a 'partial unpack' does not seem to work. def g(): return (1,2) def f(a,b,c): return a+b+c f(*g(),10) will return an error. Do you know how to get that to work? f(*(g() + (10,)) Not the most beautiful solution, but it works. Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Wed, 25 Jul 2007 15:46:58 +, beginner wrote:
On Jul 25, 10:19 am, Stargaming [EMAIL PROTECTED] wrote:
On Wed, 25 Jul 2007 14:50:18 +, beginner wrote:
[snip]
Another question is how do I pass a tuple or list of all the
aurgements of a function to the function. For example, I have all the
arguments of a function in a tuple a=(1,2,3). Then I want to pass
each item in the tuple to a function f so that I make a function call
f(1,2,3). In perl it is a given, but in python, I haven't figured out
a way to do it. (Maybe apply? but it is deprecated?)
def foo(a, b, c): print a, b, c
...
t = (1, 2, 3)
foo(*t)
1 2 3
Have a look at the official tutorial, 4.7.4http://www.python.org/doc/
current/tut/node6.html#SECTION00674
Thanks,
cg
HTH,
Stargaming
Hi Stargaming,
I know the * operator. However, a 'partial unpack' does not seem to
work.
def g():
return (1,2)
def f(a,b,c):
return a+b+c
f(*g(),10) will return an error.
http://docs.python.org/ref/calls.html
Do you know how to get that to work?
Well, there are several ways to solve this. You could either invoke f(*g
() + (10,)). Might be a bit nasty and unreadable, though. Or you could
just change your function f to accept them in reversed order (f(10, *g)
should work) or convert g() to return a dictionary like {'b': 1, 'c': 2}
and use f(10, **g). But if your function f's hugest use case is being
called with g(), changing f to accept something and g's result (tuple) --
unpacking it inside f -- might be better.
--
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Re: Flatten a list/tuple and Call a function with tuples
beginner [EMAIL PROTECTED] writes: I know the * operator. However, a 'partial unpack' does not seem to work. A few other posters have mentioned ways around this, but you might ask yourself what coding situation makes you want to do this stuff in the first place. I won't say there's never a reason for it, but a lot of times, a list containing a mixture of scalars and lists/tuples is a sign that your underlying data representation is contorted. Things are logically single values or they are logically lists of values, and that mixed representation is often a sign that the item logically should be a list, and you're hairing up the program with special treatment of the case where the list has exactly one element. I.e. instead of [[1,2,], 3, [5,6,]] maybe you really want [[1,2,], [3,], [5,6]] without the special treatment and flattening. -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
beginner wrote: On Jul 25, 10:19 am, Stargaming [EMAIL PROTECTED] wrote: On Wed, 25 Jul 2007 14:50:18 +, beginner wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. A recursive function, always yielding the first element of the list, could do the job. See the ASPN Python Cookbook for a few implementations.http://aspn.activestate.com/ASPN/search? query=flattensection=PYTHONCKBKtype=Subsection Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) def foo(a, b, c): print a, b, c ... t = (1, 2, 3) foo(*t) 1 2 3 Have a look at the official tutorial, 4.7.4http://www.python.org/doc/ current/tut/node6.html#SECTION00674 Thanks, cg HTH, Stargaming Hi Stargaming, I know the * operator. However, a 'partial unpack' does not seem to work. def g(): return (1,2) def f(a,b,c): return a+b+c f(*g(),10) will return an error. Do you know how to get that to work? Thanks, cg Were this not hypothetical, I would make use of the commutative property of addition: f(10, *g()) Proof: 1+2+10 = 10+1+2 Also, this has not been suggested: py def g(): ... return (1,2) ... py def f(a,b,c): ... return a+b+c ... py f(c=10, *g()) 13 James -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
[EMAIL PROTECTED] wrote: On Jul 25, 9:50 am, beginner [EMAIL PROTECTED] wrote: Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) I'm not sure about the first question, but as for the second, you could do a few different things. You could just pass the tuple itself into the function and have the tuple unpacked inside the function. OR you could use the syntax invented for just that purpose ;). t = 1, 2, 3 f(*t) bam! :) This works with dicts as well (for giving keyword arguments). There you prepend ** (two asterisk to your dict). Simple :) /W -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 8:46 am, beginner [EMAIL PROTECTED] wrote: On Jul 25, 10:19 am, Stargaming [EMAIL PROTECTED] wrote: On Wed, 25 Jul 2007 14:50:18 +, beginner wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. A recursive function, always yielding the first element of the list, could do the job. See the ASPN Python Cookbook for a few implementations.http://aspn.activestate.com/ASPN/search? query=flattensection=PYTHONCKBKtype=Subsection Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) def foo(a, b, c): print a, b, c ... t = (1, 2, 3) foo(*t) 1 2 3 Have a look at the official tutorial, 4.7.4http://www.python.org/doc/ current/tut/node6.html#SECTION00674 Thanks, cg HTH, Stargaming Hi Stargaming, I know the * operator. However, a 'partial unpack' does not seem to work. def g(): return (1,2) def f(a,b,c): return a+b+c f(*g(),10) will return an error. Do you know how to get that to work? You can use the partial method from functools: import functools sum_of_three = functools.partial(f, *g())(10) -- Hope this helps, Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On 2007-07-25, Jeff [EMAIL PROTECTED] wrote:
Here's a quick flatten() function:
def flatten(obj):
if type(obj) not in (list, tuple, str):
raise TypeError(String, list, or tuple expected in
flatten().)
if len(obj) == 1:
if type(obj[0]) in (tuple, list):
return flatten(obj[0])
else:
return [obj[0]]
else:
return [obj[0]] + flatten(obj[1:])
x = [1, 2, (3, 4)]
y = (1, 2, [3, 4])
z = It even works with strings!
d = {foo: bar, baz: bat}
e = [[1], 2, 3, , 4]
f = [1, 2, 3, 4, []]
--
Neil Cerutti
--
http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 3:05 pm, Eduardo \EdCrypt\ O. Padoan [EMAIL PROTECTED] wrote: def flatten(listOfLists): return list(chain(*listOfLists)) Fromhttp://www.python.org/doc/2.4/lib/itertools-recipes.html -- EduardoOPadoan (eopadoan-altavix::com) Bookmarks:http://del.icio.us/edcrypt That doesn't necessarily work: import itertools x = (1, 2, [3, 4, (5, 6)]) y = ([1, 2, (3, 4)], 5, 6) z = (1, [2, 3, (4, 5)], 6) def flatten(listOfLists): return list(itertools.chain(*listOfLists)) print flatten(x) print flatten(y) print flatten(z) == TypeError: chain argument #1 must support iteration -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
Not the most beautiful solution, but it works. Diez- Hide quoted text - - Show quoted text - Yeah it works! Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
Also, this has not been suggested: py def g(): ... return (1,2) ... py def f(a,b,c): ... return a+b+c ... py f(c=10, *g()) 13 James- Hide quoted text - - Show quoted text - Great idea. -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 11:33 am, Paul Rubin http://[EMAIL PROTECTED] wrote: beginner [EMAIL PROTECTED] writes: I know the * operator. However, a 'partial unpack' does not seem to work. A few other posters have mentioned ways around this, but you might ask yourself what coding situation makes you want to do this stuff in the first place. I won't say there's never a reason for it, but a lot of times, a list containing a mixture of scalars and lists/tuples is a sign that your underlying data representation is contorted. Things are logically single values or they are logically lists of values, and that mixed representation is often a sign that the item logically should be a list, and you're hairing up the program with special treatment of the case where the list has exactly one element. I.e. instead of [[1,2,], 3, [5,6,]] maybe you really want [[1,2,], [3,], [5,6]] without the special treatment and flattening. Very good question. It is well possible that the problem is my programming style. I am new to python and am still developing a style that works for me. A lot of things that work in perl does not seem to work. Unpacking and flattening are just two examples. I need nested lists to represent nested records in a script. Since the structure of the underlying data is nested, I think it is probably reasonable to represent them as nested lists. For example, if I have the below structure: Big Record Small Record Type A Many Small Record Type B Small Record Type C It is pretty natural to use lists, although after a while it is difficult to figure out the meaning of the fields in the lists. If only there were a way to 'attach' names to members of the list. For the unpacking question, I encountered it when working with list comprehensions. For example: [ f(*x,1,2) for x in list] is difficult to do if I don't want to expand *x to x[0]..x[n]. There are usually 7-10 items in the list and it is very tedious and error prone. The second problem is from a nested list comprehension. I just needed something to flatten the list at the moment. I am still forming my way to do things in python via trial and error. It is well possible that this is not the natural way to do things. -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
Well, there are several ways to solve this. You could either invoke f(*g
() + (10,)). Might be a bit nasty and unreadable, though. Or you could
just change your function f to accept them in reversed order (f(10, *g)
should work) or convert g() to return a dictionary like {'b': 1, 'c': 2}
and use f(10, **g). But if your function f's hugest use case is being
called with g(), changing f to accept something and g's result (tuple) --
unpacking it inside f -- might be better.- Hide quoted text -
- Show quoted text -
These all work. Thanks.
--
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Re: Flatten a list/tuple and Call a function with tuples
def flatten(listOfLists): return list(chain(*listOfLists)) From http://www.python.org/doc/2.4/lib/itertools-recipes.html -- EduardoOPadoan (eopadoan-altavix::com) Bookmarks: http://del.icio.us/edcrypt -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
For example, if I have
the below structure:
Big Record
Small Record Type A
Many Small Record Type B
Small Record Type C
It is pretty natural to use lists, although after a while it is
difficult to figure out the meaning of the fields in the lists. If
only there were a way to 'attach' names to members of the list.
You could use dictionaries:
big_record = {
small_record_a: { ... },
many_small_record_b: {
sub_record_of_b: { ... },
sub_record_of_b2: { ... },
},
small_record_c: { ... },
}
--
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Re: Flatten a list/tuple and Call a function with tuples
On Wed, 25 Jul 2007 15:46:58 +, beginner wrote: I know the * operator. However, a 'partial unpack' does not seem to work. def g(): return (1,2) def f(a,b,c): return a+b+c f(*g(),10) will return an error. No it doesn't, it _raises_ an exception. This is a function that returns an error: def function(): Returns an error. return Error() # defined elsewhere But to answer your question: Do you know how to get that to work? It's a little bit messy, but this works: f(*(g() + (10,))) 13 This is probably easier to read: t = g() + (10,); f(*t) 13 -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Wed, 25 Jul 2007 09:33:26 -0700, Paul Rubin wrote: Things are logically single values or they are logically lists of values Except for strings, and string-like objects. And files. And records/structs, and tuples. And lists. And sets. And bit strings. And tree-like structures. And, well, just about everything really. But apart from those minor exceptions, I agree completely with your recommendation. (Ha ha only serious.) -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On 2007-07-25, Neil Cerutti [EMAIL PROTECTED] wrote:
On 2007-07-25, Jeff [EMAIL PROTECTED] wrote:
Here's a quick flatten() function:
def flatten(obj):
if type(obj) not in (list, tuple, str):
raise TypeError(String, list, or tuple expected in
flatten().)
if len(obj) == 1:
if type(obj[0]) in (tuple, list):
return flatten(obj[0])
else:
return [obj[0]]
else:
return [obj[0]] + flatten(obj[1:])
x = [1, 2, (3, 4)]
y = (1, 2, [3, 4])
z = It even works with strings!
d = {foo: bar, baz: bat}
e = [[1], 2, 3, , 4]
Please excuse my bad typography. The above should've been
e = [[1], 2, 3, 4].
--
Neil Cerutti
It isn't pollution that is hurting the environment; it's the impurities in our
air and water that are doing it. --Dan Quayle
--
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Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 10:33 am, Jeff [EMAIL PROTECTED] wrote: def flatten(obj): if type(obj) not in (list, tuple, str): raise TypeError(String, list, or tuple expected in flatten().) if len(obj) == 1: if type(obj[0]) in (tuple, list): return flatten(obj[0]) else: return [obj[0]] else: return [obj[0]] + flatten(obj[1:]) This seems to work fine only if the last object is the only one with the tuple or list. For example: y = [(1,2),3,4] y [(1, 2), 3, 4] print flatten(y) [(1, 2), 3, 4] if the last line is changed to return flatten([obj[0]]) + flatten(obj[1:]) then it will unpack tuples/lists anywhere in the main collection being flattened: y [(1, 2), 3, 4] flatten(y) [1, 2, 3, 4] z = [1,(2,3),4] flatten(z) [1, 2, 3, 4] x [1, 2, (3, 4)] flatten(x) [1, 2, 3, 4] k = [(1,2),(3,4)] flatten(k) [1, 2, 3, 4] -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
On Jul 25, 12:00 pm, [EMAIL PROTECTED] wrote: On Jul 25, 10:46 am, beginner [EMAIL PROTECTED] wrote: On Jul 25, 10:19 am, Stargaming [EMAIL PROTECTED] wrote: On Wed, 25 Jul 2007 14:50:18 +, beginner wrote: Hi, I am wondering how do I 'flatten' a list or a tuple? For example, I'd like to transform[1, 2, (3,4)] or [1,2,[3,4]] to [1,2,3,4]. A recursive function, always yielding the first element of the list, could do the job. See the ASPN Python Cookbook for a few implementations.http://aspn.activestate.com/ASPN/search? query=flattensection=PYTHONCKBKtype=Subsection Another question is how do I pass a tuple or list of all the aurgements of a function to the function. For example, I have all the arguments of a function in a tuple a=(1,2,3). Then I want to pass each item in the tuple to a function f so that I make a function call f(1,2,3). In perl it is a given, but in python, I haven't figured out a way to do it. (Maybe apply? but it is deprecated?) def foo(a, b, c): print a, b, c ... t = (1, 2, 3) foo(*t) 1 2 3 Have a look at the official tutorial, 4.7.4http://www.python.org/doc/ current/tut/node6.html#SECTION00674 Thanks, cg HTH, Stargaming Hi Stargaming, I know the * operator. However, a 'partial unpack' does not seem to work. def g(): return (1,2) def f(a,b,c): return a+b+c f(*g(),10) will return an error. Do you know how to get that to work? Thanks, cg As I mentioned, you can access the elements individually using square brackets. The following works: f(g()[0], g()[1], 10) But it's not clear. Unfortunately, I'm not seeing much else for tuple unpacking except the obvious: a,b=g() f(a,b,10) Mike Or if you'd rather write it in one line: f(*(g() + (10,))) George -- http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
Here's a quick flatten() function:
def flatten(obj):
if type(obj) not in (list, tuple, str):
raise TypeError(String, list, or tuple expected in
flatten().)
if len(obj) == 1:
if type(obj[0]) in (tuple, list):
return flatten(obj[0])
else:
return [obj[0]]
else:
return [obj[0]] + flatten(obj[1:])
x = [1, 2, (3, 4)]
y = (1, 2, [3, 4])
z = It even works with strings!
d = {foo: bar, baz: bat}
print flatten(x)
print flatten(y)
print flatten(z)
print flatten(d)
--
http://mail.python.org/mailman/listinfo/python-list
Re: Flatten a list/tuple and Call a function with tuples
Sorry about that. Hopefully, this should work ;) def flatten(obj): if type(obj) not in (list, tuple, str): raise TypeError(String, list, or tuple expected in flatten().) if len(obj) == 1: if type(obj[0]) in (tuple, list): return flatten(obj[0]) else: return [obj[0]] else: if type(obj[0]) in (list, tuple): return flatten(obj[0]) + flatten(obj[1:]) else: return [obj[0]] + flatten(obj[1:]) x = (1, 2, [3, 4, (5, 6)]) y = ([1, 2, (3, 4)], 5, 6) z = (1, [2, 3, (4, 5)], 6) print flatten(x) print flatten(y) print flatten(z) -- http://mail.python.org/mailman/listinfo/python-list
