CODEWITHSUNDEEP
pythonlist
iam_agf
iam_agf

Reputation: 689

Objects between objects python

I want to make from the list:

L=[1,2,3,4,5,6,7,8,9]

This:

L=[1,1,1,2,1,3,1,4,1,5,1,6,1,7,1,8,1,9]

This is, put the 1 between the objects in list. Can someone help me?

Upvotes: 2

Views: 69

Answers (5)

Steve Jessop
Steve Jessop

Reputation: 279285

For the result in your example (1 before each object):

L = [y for x in L for y in (1, x)]

For the result described by your text (1 between the objects):

L = [y for x in L for y in (x, 1)]
L.pop()

If you hate multiple for clauses in comprehensions:

L = list(itertools.chain.from_iterable((1, x) for x in L))

Upvotes: 4

jterrace
jterrace

Reputation: 67073

Using itertools:

>>> L=[1,2,3,4,5,6,7,8,9]
>>> from itertools import chain, izip, repeat
>>> list(chain.from_iterable(izip(repeat(1), L)))
[1, 1, 1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 8, 1, 9]

Upvotes: 0

Dylan Lawrence
Dylan Lawrence

Reputation: 1533

A simple for loop would suffice

for item in list:
  newList.append(1)
  newList.append(item)
list = newList

Upvotes: 1

mgilson
mgilson

Reputation: 309959

I've always really loved slice assignment:

>>> L = range(1, 10)
>>> L
[1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> # Done with setup, let the fun commence!
>>> LL = [None] * (len(L)*2)  # Make space for the output
>>> LL[1::2] = L
>>> LL[::2] = [1] * len(L)

>>> LL  # Lets check the results, shall we?
[1, 1, 1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 8, 1, 9]

Upvotes: 2

thefourtheye
thefourtheye

Reputation: 239513

print ([i for t in zip([1] * len(L), L) for i in t])

Output

[1, 1, 1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 8, 1, 9]

Upvotes: 2

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