Combine List Elements In Groups Of Two With A Delimiter

May 30, 2023 Post a Comment

I have a list of words and their meanings: wm = ['mendacious', 'dishonest', 'mendicant', 'beggar', 'meretricious', 'gaudy; specious; falsely attractive', 'mesmerize', 'to hy

Solution 1:

You need to iterator over the list in pairs, and there's a simple idiom to do this by ziping up 2 of the same iter:

>>> i = iter(wm)
>>> [' : '.join(s) for s inzip(i, i)]
['mendacious : dishonest',
 'mendicant : beggar',
 'meretricious : gaudy; specious; falsely attractive',
 'mesmerize : to hypnotize',
 'metamorphosis : change; transformation']

Solution 2:

A pythonic way of doing it:

res = ["%s : %s" % (wm[i], wm[i+1]) for i in range(0, len(wm), 2)]
print(res)

['mendacious : dishonest','mendicant : beggar','meretricious : gaudy; specious; falsely attractive','mesmerize : to hypnotize', 'metamorphosis : change; transformation']

Solution 3:

You can simply create a list of tuples using this code:

tl = zip(wm[0::2], wm[1::2])

This list will look like the following list:

[('mendacious', 'dishonest'), ('mendicant', 'beggar'), ('meretricious', 'gaudy; specious; falsely attractive'), ('mesmerize', 'to hypnotize'), ('metamorphosis', 'change; transformation')]

Then you can iterate through this list and concatenate each tuple.

#1

output = map(lambda t: t[0] + ':' + t[1], tl)

#2

output = [':'.join(t) for t in tl]

Solution 4:

My answer is very similar to AChampion's:

wm = [
    'mendacious',
    'dishonest',
    'mendicant',
    'beggar',
    'meretricious',
    'gaudy; specious; falsely attractive',
    'mesmerize',
    'to hypnotize',
    'metamorphosis',
    'change; transformation'
]

a = list(map(' : '.join, zip(*[iter(wm)] * 2)))
print(a)

This code may be a bit mysterious, so I'll try to explain what's going on.

iter(wm) creates an iterator object from wm. As the docs say, this is

an object representing a stream of data. Repeated calls to the iterator’s __next__() method (or passing it to the built-in function next()) return successive items in the stream.

We then duplicate the iterator and zip it. This lets us iterate over the items from the pair of iterators in parallel. But we don't actually have two separate iterators: we have two references to the one iterator object, so what we get is successive pairs of the items in wm. FWIW, this technique is discussed in How do you split a list into evenly sized chunks?.

We use map to call the ' : '.join method on each tuple of strings yielded by zip. Finally, we use list to convert the iterable returned by map into a list (in Python 2 this step isn't needed since the Python 2 map returns a list).

We can use this same technique to produce a dictionary instead of a list. A dictionary is a more useful structure for this data.

d = {k: v for k, v inzip(*[iter(wm)] * 2)}
print(d)

output

{'metamorphosis': 'change; transformation', 'mendicant': 'beggar', 'mendacious': 'dishonest', 'mesmerize': 'to hypnotize', 'meretricious': 'gaudy; specious; falsely attractive'}

And we can split the v strings into lists, which makes it easier to get at the individual words:

d = {k: v.split('; ') for k, v inzip(*[iter(wm)] * 2)}
print(d)