Is there a function which takes a list of tuples and returns a list of
lists made up of the first element of each tuple, the second element of
each tuple, etc.?
In other words, the the inverse of the builtin zip function?
David 6 7226
Terry Reedy wrote: "David C. Fox" <da*******@post.harvard.edu> wrote in message news:9sBVa.12998$o%2.6289@sccrnsc02...
Is there a function which takes a list of tuples and returns a list
of
lists made up of the first element of each tuple, the second element
of
each tuple, etc.?
In other words, the the inverse of the builtin zip function?
Go to http://groups.google.com/groups?hl=e...mp.lang.python enter 'zip inverse', and check search Python only.
TJR
Thanks. I've gotten so used to reading this group with Mozilla Mail
that I forgot about google groups.
David
On Tue, 29 Jul 2003 22:06:20 +0000, Raymond Hettinger wrote: "David C. Fox" <da*******@post.harvard.edu> wrote in message news:9sBVa.12998$o%2.6289@sccrnsc02... Is there a function which takes a list of tuples and returns a list of lists made up of the first element of each tuple, the second element of each tuple, etc.?
In other words, the the inverse of the builtin zip function?
When used with the * operator, zip() is its own inverse:
This (obviously) doesn't work when z has length 0 or 2.
I don't quite understand why zip is overloaded ...
Oh, hang on, it does work for length 2! that's neato,
and perhaps that's why zip was extended. Is it a functional programming
convention, i wonder.
Simon.
On Wed, 30 Jul 2003 08:31:47 +1000, Simon Burton wrote: On Tue, 29 Jul 2003 22:06:20 +0000, Raymond Hettinger wrote:
"David C. Fox" <da*******@post.harvard.edu> wrote in message news:9sBVa.12998$o%2.6289@sccrnsc02... Is there a function which takes a list of tuples and returns a list of lists made up of the first element of each tuple, the second element of each tuple, etc.?
In other words, the the inverse of the builtin zip function?
When used with the * operator, zip() is its own inverse:
OK, i think i see now. it's swapping rows<>columns, and might help this
other guy with his gridcontrols. But zip() should return (). No?
Simon.
> >> In other words, the the inverse of the builtin zip function? When used with the * operator, zip() is its own inverse:
This (obviously) doesn't work when z has length 0 or 2. I don't quite understand why zip is overloaded ...
Oh, hang on, it does work for length 2! that's neato, and perhaps that's why zip was extended. Is it a functional programming convention, i wonder.
Simon.
There is no special extension to zip().
It just happens to be one of those functions
like int.__neg__() that is closely related to
its own inverse.
* or apply() serve only to break a list into
individual arguments. So, transpose() can
be defined like this:
def transpose(mat):
return zip(*mat)
The transpose() is its own inverse for rectangular
matrices represented as lists of tuples.
Raymond Hettinger
Raymond Hettinger wrote: >> In other words, the the inverse of the builtin zip function? > > When used with the * operator, zip() is its own inverse: There is no special extension to zip(). It just happens to be one of those functions like int.__neg__() that is closely related to its own inverse.
* or apply() serve only to break a list into individual arguments. So, transpose() can be defined like this:
I understand why it works as inverse when *<list> creates a argument list of
list element. But don't understand why * works that way in this context.
Does ** do this for maps and keywordargs, too? Hey, this is python  lets
try: def foo(a=None, b=None):
.... pass
.... foo(a=10, b=20) foo(**{'a':10, 'b':20})
Coooool. Where is that documented? Never stumbled across it so far!
Diez
> I understand why it works as inverse when *<list> creates a argument list of list element. But don't understand why * works that way in this context. Does ** do this for maps and keywordargs, too? Hey, this is python  lets try: def foo(a=None, b=None): ... pass ... foo(a=10, b=20) foo(**{'a':10, 'b':20})
Coooool. Where is that documented? Never stumbled across it so far! http://www.python.org/dev/doc/devel/ref/calls.html
Raymond Hettinger This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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