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 built-in zip function?
David 6 7335
Terry Reedy wrote: "David C. Fox" <da*******@post.harvard.edu> wrote in message news:9sBVa.12998$o%2.6289@sccrnsc02...
Is there a function which takes a list of tuples and returns a list
of
lists made up of the first element of each tuple, the second element
of
each tuple, etc.?
In other words, the the inverse of the built-in zip function?
Go to http://groups.google.com/groups?hl=e...mp.lang.python enter 'zip inverse', and check search Python only.
TJR
Thanks. I've gotten so used to reading this group with Mozilla Mail
that I forgot about google groups.
David
On Tue, 29 Jul 2003 22:06:20 +0000, Raymond Hettinger wrote: "David C. Fox" <da*******@post.harvard.edu> wrote in message news:9sBVa.12998$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 built-in 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 neat-o,
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 built-in 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 built-in 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 neat-o, 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 built-in 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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