Loops and Strings in python

Question

Given the strings s1 and s2, not necessarily of the same length. Create a new string consisting of alternating characters of s1 and s2 (that is, the first character of s1 followed by the first character of s2, followed by the second character of s1, followed by the second character of s2, and so on.

Once the end of either string is reached, the remainder of the longer string is added to the end of the new string. For example, if s1 contained "abc" and s2 contained "uvwxyz", then the new string should contain "aubvcwxyz". Associate the new string with the variable s3.

My attempt is:

s3 = '' 
i = 0 
while i < len(s1) and i < len(s2): 
    s3 += s1[i] + s2[i] 
    i += 1 
    if len(s1) > len(s2): 
        s3 += s1[i:] 
    elif len(s2) > len(s1): 
        s3 += s2[i:]

You should give it a try yourself and let us see what you did and where you got stucked to help you out ! — Iron Fist
– Iron Fist, Commented Jul 11, 2015 at 3:31
s3 = '' for i in range(0, min(len(s1), len(s2))): s3 = s3 + s1[i] + s2[i] — Zhanna D.
– Zhanna D., Commented Jul 11, 2015 at 3:32
Better post it in your Question...Never be shame of what you tried...:) — Iron Fist
– Iron Fist, Commented Jul 11, 2015 at 3:32
s3 = '' i = 0 while i < len(s1) and i < len(s2): s3 += s1[i] + s2[i] i += 1 if len(s1) > len(s2): s3 += s1[i:] elif len(s2) > len(s1): s3 += s2[i:] what about this ? — Zhanna D.
– Zhanna D., Commented Jul 11, 2015 at 3:40
You should edit your question to include the info you're currently giving us — NightShadeQueen
– NightShadeQueen, Commented Jul 11, 2015 at 3:47

Community · Accepted Answer · 2017-05-23 10:26:46Z

3

s1 = "abcdefg"
s2 = "hijk"
s3 = ""
minLen = min(len(s1), len(s2))
    for x in range(minLen):
    out += s1[x]
    out += s2[x]
out += s1[minLen:]
print out

A couple of things to keep in mind. First, you can treat a python string like an array, and you can access the item at given index using brackets. Also, the second to last line makes use of splicing, for more information, see How can I splice a string?

edited May 23, 2017 at 10:26

CommunityBot

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answered Jul 11, 2015 at 3:27

altblahblah

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Comments

Iron Fist · Accepted Answer · 2015-07-11 04:04:21Z

1

You can do it using izip_longest method from itertools module, this way:

import itertools as it
s3 = ''.join(''.join(item) for item in it.izip_longest(s1,s2,fillvalue=''))

DEMONSTRATION:

>>> s1 = 'ABCDEF'
>>> s2 = '123456789'
>>> s3 = ''.join(''.join(item) for item in it.izip_longest(s1,s2,fillvalue=''))
>>> 
>>> s3
'A1B2C3D4E5F6789'

EDIT: in avoiding multiple join:

s3 = ''.join(c for item in it.izip_longest(s1,s2,fillvalue='') for c in item)

edited Jul 11, 2015 at 4:04

answered Jul 11, 2015 at 3:42

Iron Fist

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4 Comments

tiho Over a year ago

I would suggest the following to avoid the multiple joins (which are probably less efficient):''.join(c for item in it.izip_longest(s1,s2,fillvalue='') for c in item)

Iron Fist Over a year ago

@tiho...thanks for the comment, will update the answer..:)

msw Over a year ago

Although izip_longest was my first thought, i'm going to have to go with @altblahblah for "grader-friendliness" and "student comprehension". Thanks for trying to teach the OP protocol round here.

Iron Fist Over a year ago

@msw, that's right, the OP seems to learn Python and altblahblah answer is more comprehensive, just like you said .. :)

A K · Accepted Answer · 2015-07-11 04:06:28Z

0

a = 'abc'
b= 'uxyz'
c=''
t=0

while t<len(a):
    c+=a[t]+b[t]
    t+=1

c+=b[t:]
print(c)

This should be the bare minimum for you to tweak some more so you learn from this. I suggest adding some conditionals and turning it into a function so it can take so s1 and s2 can be any length and it will still work. That'll be fun~

answered Jul 11, 2015 at 4:06

A K

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Comments

Orkun Berk Yuzbasioglu · Accepted Answer · 2018-11-03 14:28:33Z

0

In python3.x, the following code block works, because Python slices return all of elements in range or an empty string if the index values aren't valid for that string:

n = min(len(s1),len(s2))
s3=""

for i in range(0,n):
    s3 = s3 + s1[i] + s2[i]

s3 = s3 + s1[n:] + s2[n:]

answered Nov 3, 2018 at 14:28

Orkun Berk Yuzbasioglu

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Comments

Mustafa Kurt · Accepted Answer · 2018-11-20 21:44:37Z

0

we can first decide which string is longer then write a for loop for that condition.

s3 = ""
i=0
if len(s1)>len(s2):
    for i in range(len(s2)) :
        s3 = s3 + s1[i] + s2[i]
        i=i+1
    s3=s3+s1[i:]
else:
    for i in range(len(s1)) :
        s3 = s3 + s1[i] + s2[i]
        i=i+1
    s3=s3+s2[i:]

edited Nov 20, 2018 at 21:44

answered Nov 20, 2018 at 21:34

Mustafa Kurt

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Comments

huan wang · Accepted Answer · 2020-04-07 14:59:31Z

-1

i = 0
s3 = ''
minLen = min(len(s1),len(s2))
while i < minLen:
    s3 = s3+ s1[i] + s2[i]
    i += 1
if maxLen != minLen:
    s3 += s1[minLen:]+s2[minLen:]

answered Apr 7, 2020 at 14:59

huan wang

1

2 Comments

sooobus Over a year ago

How maxLen is used?

Youssef Over a year ago

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