CODEWITHSUNDEEP
pythonlistfilter
kollo
kollo

Reputation: 1311

get items 2 by 2 from a list in Python

What is the most elegant way to obtain items 2 by 2 from a list ?

from:
my_list = ['I', 'swear', 'I', 'googled', 'first']

to:
res_list = ['I swear', 'swear I', 'I googled', 'googled first']

Upvotes: 1

Views: 488

Answers (5)

ListenSoftware Louise Ai Agent
ListenSoftware Louise Ai Agent

Reputation: 4243

my_list = ['I', 'swear', 'I', 'googled', 'first']

def two_words(my_list):
   i=0
   words=[]
   for word in my_list:
    
        words.append(word)
        if i%2:
            yield (" ".join(words))
            words.clear()
        i+=1
    if len(words)>0:
        yield (" ".join(words))
    
print(list(two_words(my_list)))

output:

 ['I swear', 'I googled', 'first']

Upvotes: 0

anon582847382
anon582847382

Reputation: 20361

A neat little one-liner in the form of a generator expression:

>>> my_list = ['I', 'swear', 'I', 'googled', 'first']
>>> res_list = (' '.join((x, y)) for x, y in zip(my_list, my_list[1:]))
>>> list(res_list)
['I swear', 'swear I', 'I googled', 'googled first']

Upvotes: 0

unutbu
unutbu

Reputation: 879591

def window(seq, n=2):
    """
    Returns a sliding window (of width n) over data from the sequence
    s -> (s0,s1,...s[n-1]), (s1,s2,...,sn), ...
    """
    for i in xrange(len(seq)-n+1):
        yield tuple(seq[i:i+n])

my_list = ['I', 'swear', 'I', 'googled', 'first']
res_list = [' '.join(group) for group in window(my_list, 2)]
print(res_list)
# ['I swear', 'swear I', 'I googled', 'googled first']

Upvotes: 5

Hyperboreus
Hyperboreus

Reputation: 32429

I would say a standard case for zip:

def pairs(i):
    return list(zip(i, i[1:]))

my_list = ['I', 'swear', 'I', 'googled', 'first']
res_list = pairs(my_list)
print(res_list)
# [('I', 'swear'), ('swear', 'I'), ('I', 'googled'), ('googled', 'first')]
print([' '.join(a) for a in res_list])
# ['I swear', 'swear I', 'I googled', 'googled first']

Just for completeness's sake, the same with arbitrary window width:

def window(i, n = 2):
    return list(zip(*(i[p:] for p in range(n))))

Upvotes: 1

M4rtini
M4rtini

Reputation: 13539

def pairwise( iterable, n=2 ):
    from itertools import tee, izip, islice
    return izip(*(islice(it,pos,None) for pos,it in enumerate(tee(iterable, n))))

my_list = ['I', 'swear', 'I', 'googled', 'first']

print list(pairwise(my_list))
#[('I', 'swear'), ('swear', 'I'), ('I', 'googled'), ('googled', 'first')]

Upvotes: 1

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