How to add two strings by index

Question

I tried many times but could not do it.

Here is an example:

print( concat_corresponding( "12345", "6789XYZ" ) )

Desired output:

162738495XYZ

show us what you've tried...show us `concat_corresponding` code. Is `162738495XYZ` the expected output or what you're getting? — depperm, Apr 27 '18 at 19:10
Did an answer below help? Feel free to accept an answer (green tick on left), or ask for clarification. — jpp, May 08 '18 at 11:14

jpp · Answer 1 · 2018-04-27T19:53:42.260

3

This is one way with itertools:

from itertools import chain, zip_longest

a = "12345"
b = "6789XYZ"

res = ''.join(list(chain.from_iterable(zip_longest(a, b, fillvalue=''))))

# '162738495XYZ'

Note the list conversion is not required, but improves performance.

edited Apr 27 '18 at 19:53

answered Apr 27 '18 at 19:24

jpp

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Patrick Artner · Answer 2 · 2018-04-27T19:26:00.737

2

You can levarege list comprehensions, join and zip:

te1 = "12345"
te2 = "6789XYZ"

print (''.join( ''.join(x) for x in zip(te1,te2)) + (te1[len(te2):] if len(te1)>len(te2) else te2[len(te1):]))
                                                    # ^^^^ this part adds the remainer of longer list to result

output:

162738495XYZ

https://docs.python.org/3/library/functions.html#zip

https://docs.python.org/3/library/stdtypes.html#str.join

Explanation:

zip pairs up the characters by position, the rest makes the list of pairs back into a string.

Zip only works for the shorter length string - you can switch to itertools.zip_longest (see JimDennis answer) or append the longer lists part (like I did here)

itertools.zip_longest(*iterables, fillvalue=None)

edited Apr 27 '18 at 19:26

answered Apr 27 '18 at 19:13

Patrick Artner

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This cuts off YZ since the strings are of different lengths. – W Stokvis Apr 27 '18 at 19:17
2

Yeah, need to either zip up the slices that can be matched (and then append a slice from the longer one ... or use something like *itertools.izip_longest()* and munge the None values into empty strings (see my answer). – Jim Dennis Apr 27 '18 at 19:18
1

@WStokvis fixed that – Patrick Artner Apr 27 '18 at 19:19
@JimDennis thanks for the comment, was just editing that ;)# – Patrick Artner Apr 27 '18 at 19:19

Jim Dennis · Answer 3 · 2018-04-27T20:58:18.550

2

from itertools import izip_longest
''.join(['%s%s' % (x ,y)\
         for x,y in izip_longest("12345","6789XYZ", fillvalue='')])

## Was: ''.join(['%s%s' % (x if x else '',y if y else '') \
##         for x,y in izip_longest("12345","6789XYZ")])

To break that down a bit:

the builtin zip() function zips only to the shorter of the two sequences; so we use izip_longest() from the itertools standard library module
izip_longest() pads the generated sequences with None by default; so we add the fillvalue='' optional (keyword) argument
the resulting substrings are all just joined together to form your results.

edited Apr 27 '18 at 20:58

answered Apr 27 '18 at 19:17

Jim Dennis

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You can simply give `''` as fillvalue: [itertools.zip_longest(*iterables, fillvalue=None)](https://docs.python.org/3/library/itertools.html#itertools.zip_longest) no need to munge – Patrick Artner Apr 27 '18 at 19:24

score 1 · Answer 4 · answered Apr 27 '18 at 19:24

1

I think this solution is a little cleaner and takes advantage of the fillvalue keyword argument for itertools.zip_longest.

from itertools import zip_longest 

''.join(a+b for a, b in zip_longest(s1, s2, fillvalue=''))

answered Apr 27 '18 at 19:24

bphi

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A.Raouf · Answer 5 · 2018-04-27T19:24:58.653

0

This one is basic but useful

str1="12345"
str2="6789XYZ"
str3=""
i=0
for i, ch in enumerate(zip(str1, str2)):
    str3 += ch[0] + ch[1]

if len(str1) < len(str2):
    str3 += str2[i+1:]
else:
    str3 += str1[i+1:]
print(str3)

edited Apr 27 '18 at 19:24

answered Apr 27 '18 at 19:11

A.Raouf

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score 0 · Answer 6 · answered Apr 27 '18 at 19:44

Another way of doing it is the following:

def concat_corresponding(string1, string2):
    minimum, maximum = sorted([string1, string2], key=len)
    return "".join(string1[i]+string2[i] for i in range(len(minimum))) + maximum[len(minimum):]

print(concat_corresponding( "12345", "6789XYZ" ))

Output:

162738495XYZ

How to add two strings by index

6 Answers6