Flatten a list/tuple and Call a function with tuples

[beginner]

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

[kyosohma@gmail.com]

Re: Flatten a list/tuple and Call a function with tuples

On Jul 25, 9:50 am, beginner <zyzhu2...@gmai l.comwrote:

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

[Stargaming]

Re: Flatten a list/tuple and Call a function with tuples

On Wed, 25 Jul 2007 14:50:18 +0000, 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=flatten&s ection=PYTHONCK BK&type=Subsect ion

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#SECT ION006740000000 000000000

Thanks,
cg

HTH,
Stargaming

[beginner]

Re: Flatten a list/tuple and Call a function with tuples

On Jul 25, 10:19 am, Stargaming <stargam...@gma il.comwrote:

On Wed, 25 Jul 2007 14:50:18 +0000, 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=flatten&s ection=PYTHONCK BK&type=Subsect ion
>

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#SECT ION006740000000 000000000
>

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

[kyosohma@gmail.com]

Re: Flatten a list/tuple and Call a function with tuples

On Jul 25, 10:46 am, beginner <zyzhu2...@gmai l.comwrote:

On Jul 25, 10:19 am, Stargaming <stargam...@gma il.comwrote:
>
>
>

On Wed, 25 Jul 2007 14:50:18 +0000, 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=flatten&s ection=PYTHONCK BK&type=Subsect ion

>

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#SECT ION006740000000 000000000

>

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

[beginner]

Re: Flatten a list/tuple and Call a function with tuples

On Jul 25, 11:00 am, kyoso...@gmail. com wrote:

On Jul 25, 10:46 am, beginner <zyzhu2...@gmai l.comwrote:
>
>
>
>
>

On Jul 25, 10:19 am, Stargaming <stargam...@gma il.comwrote:

>

On Wed, 25 Jul 2007 14:50:18 +0000, 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=flatten&s ection=PYTHONCK BK&type=Subsect ion

>

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#SECT ION006740000000 000000000

>

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.

[Diez B. Roggisch]

Re: Flatten a list/tuple and Call a function with tuples

beginner wrote:

On Jul 25, 10:19 am, Stargaming <stargam...@gma il.comwrote:

>On Wed, 25 Jul 2007 14:50:18 +0000, 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
>implementation s.http://aspn.activestate.com/ASPN/search?
>query=flatten& section=PYTHONC KBK&type=Subsec tion
>>

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#SECT ION006740000000 000000000
>>

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

[Paul Rubin]

Re: Flatten a list/tuple and Call a function with tuples

beginner <zyzhu2000@gmai l.comwrites:

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.

[James Stroud]

Re: Flatten a list/tuple and Call a function with tuples

beginner wrote:

On Jul 25, 10:19 am, Stargaming <stargam...@gma il.comwrote:

>On Wed, 25 Jul 2007 14:50:18 +0000, 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=flatten& section=PYTHONC KBK&type=Subsec tion
>>

>>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#SECT ION006740000000 000000000
>>

>>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:

pydef g():
.... return (1,2)
....
pydef f(a,b,c):
.... return a+b+c
....
pyf(c=10, *g())
13


James

[Wildemar Wildenburger]

Re: Flatten a list/tuple and Call a function with tuples

kyosohma@gmail. com wrote:

On Jul 25, 9:50 am, beginner <zyzhu2...@gmai l.comwrote:
>

>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

[attn.steven.kuo@gmail.com]

Re: Flatten a list/tuple and Call a function with tuples

On Jul 25, 8:46 am, beginner <zyzhu2...@gmai l.comwrote:

On Jul 25, 10:19 am, Stargaming <stargam...@gma il.comwrote:
>
>
>

On Wed, 25 Jul 2007 14:50:18 +0000, 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=flatten&s ection=PYTHONCK BK&type=Subsect ion

>

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#SECT ION006740000000 000000000

>

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.parti al(f, *g())(10)


--
Hope this helps,
Steven

[George Sakkis]

Re: Flatten a list/tuple and Call a function with tuples

On Jul 25, 12:00 pm, kyoso...@gmail. com wrote:

On Jul 25, 10:46 am, beginner <zyzhu2...@gmai l.comwrote:
>
>
>

On Jul 25, 10:19 am, Stargaming <stargam...@gma il.comwrote:

>

On Wed, 25 Jul 2007 14:50:18 +0000, 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=flatten&s ection=PYTHONCK BK&type=Subsect ion

>

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#SECT ION006740000000 000000000

>

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

[Jeff]

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("Stri ng, 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)

[Aneesh Goel]

Re: Flatten a list/tuple and Call a function with tuples

On Jul 25, 10:33 am, Jeff <jeffo...@gmail .comwrote:

def flatten(obj):
if type(obj) not in (list, tuple, str):
raise TypeError("Stri ng, 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]

[Neil Cerutti]

Re: Flatten a list/tuple and Call a function with tuples

On 2007-07-25, Jeff <jeffober@gmail .comwrote:

Here's a quick flatten() function:
>
def flatten(obj):
if type(obj) not in (list, tuple, str):
raise TypeError("Stri ng, 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