breaking up a list

[C Gillespie]

Dear All,

If I have a list, say

x=[1,2,3,4,5,6]

What's the best way of converting it into this: [[1, 2], [3, 4], [5, 6]],
i.e. splitting it into pairs.

Many thanks

Colin

[Peter Hansen]

C Gillespie wrote:

Dear All,

If I have a list, say

x=[1,2,3,4,5,6]

What's the best way of converting it into this: [[1, 2], [3, 4], [5, 6]],
i.e. splitting it into pairs.

There are a variety of solutions in the Python Cookbook
here http://aspn.activestate.com/ASPN/Coo...kwd=Algorithms

I notice "Getting items in batches", and "Group a list into
sequential n-tuples" right off the bat.

-Peter

[Curzio Basso]

C Gillespie wrote:

Dear All,

If I have a list, say

x=[1,2,3,4,5,6]

What's the best way of converting it into this: [[1, 2], [3, 4], [5, 6]],
i.e. splitting it into pairs.

don't know if it's the best way but you can try this:

pairs = [x[2*i:2*i+2] for i in xrange(len(x)/2)]

[Peter Otten]

> If I have a list, say

x=[1,2,3,4,5,6]

What's the best way of converting it into this: [[1, 2], [3, 4], [5, 6]],
i.e. splitting it into pairs.

I like

x = [1, 2, 3, 4, 5, 6]
it = iter(x)
zip(it, it)

[(1, 2), (3, 4), (5, 6)]

even after posting it several times before :-) Use map(list, zip(it, it)) if
you need lists instead of tuples.

Michele Simionato has posted a generalized version of this recipe:
http://mail.python.org/pipermail/pyt...ay/222673.html

Peter

[Larry Bates]

C Gillespie wrote:

Dear All,

If I have a list, say

x=[1,2,3,4,5,6]

What's the best way of converting it into this: [[1, 2], [3, 4], [5, 6]],
i.e. splitting it into pairs.

Many thanks

Colin

I would use:

pairs=[[a,b] for a,b in x]

but as you can see from other replies there are other ways.
Note: this wouldn't work if there were not an EVEN number
of data items in the list.

Larry Bates
Syscon, Inc.

[Curzio Basso]

Larry Bates wrote:

x=[1,2,3,4,5,6]

pairs=[[a,b] for a,b in x]

[[a,b] for a,b in x]

TypeError: unpack non-sequence

[Alex Martelli]

Larry Bates <lb****@syscononline.com> wrote:
...

x=[1,2,3,4,5,6]

What's the best way of converting it into this: [[1, 2], [3, 4], [5, 6]],

... I would use:

pairs=[[a,b] for a,b in x]

but as you can see from other replies there are other ways.

Which is fortunate, because what you would use could never possibly work
for the value of x given by the original poster (and most other values
of x except sequences of two-items subsequences...).
Alex