List Matching, and outputting to text from multiple lists

Dev Shed Forums Sponsor:

July 15th, 2012, 03:40 AM

jepot

Registered User

Join Date: Dec 2008

Posts: 17

Time spent in forums: 5 h 17 m 23 sec
Reputation Power: 0

List Matching, and outputting to text from multiple lists

Say I have two lists like:

Code:

a = ['', '2', '3', '4', '']
b = ['1', '5']

List a has strings and has some items which are empty strings
List b has some strings but no empty ones. The length of b is always less than a.

How can I fill list a by checking every item in a to see if it is an empty string, taking the first item out of b (then removing it from b), and using this item in place of the empty string in a? so that I have a list like:

Code:

c = ['1', '2', '3', '4', '5']

Also, say I have 3 lists, all of the same length. How can I print to a text file the first item in list 1, a space, the first item in list 2, another space and the first item in list 3. Then do the same for the next line, only this time use the second item and so on...? Eg

Code:

a = ['1', '2', '3', '4', '5']
b = ['hi', 'are', 'you', 'ok', '?']
c = ['yes', 'i', 'am', 'y', '?']

and output to a txt file...

Code:

1 hi yes
2 are i
3 you am
4 ok y
5 ? ?

July 15th, 2012, 08:18 AM

b49P23TIvg

Contributing User

Join Date: Aug 2011

Posts: 3,393

Time spent in forums: 1 Month 2 Weeks 3 Days 15 h 37 m 10 sec
Reputation Power: 383

The answer to your second question comes more easily:

Code:

>>> # you need zip
>>> # succinctly:
>>> print('\n'.join(' '.join(t)for t in zip(a,b,c)))
1 hi yes
2 are i
3 you am
4 ok y
5 ? ?
>>> # simplified
>>> for t in zip(a,b,c):
...     print(' '.join(t))
... 
1 hi yes
2 are i
3 you am
4 ok y
5 ? ?
>>>

Code:

def jepot_substitute(a,b):
    result = a[:]
    j = 0
    for i in range(len(result)):
        if j == len(b):
            break
        if not result[i]:
            result[i] = b[j]
            j += 1
    return result

print(jepot_substitute(['', '2', '3', '4', ''],['1', '5']))
print(jepot_substitute(['', '2', '3', '4', ''],['short',]))
print(jepot_substitute(['', '2', '3', '4', ''],['1','bark','unused']))

__________________
[code]Code tags[/code] are essential for python code!

July 15th, 2012, 10:11 AM

SuperOscar

Contributing User

Join Date: Jul 2007

Location: Joensuu, Finland

Posts: 404

Time spent in forums: 1 Week 5 h 18 m 4 sec
Reputation Power: 65

Or even:

Code:

from collections import deque
def jepot_substitute(a, b):
    b = deque(b)
    return [s if s != '' else b.popleft() for s in a]

(Sorry for the multiple edits of this post – I guess this is now the definitive version...)

__________________
My armada: openSUSE 12.3 (home desktop, laptop, work desktop), Ubuntu 12.04 LTS (mini laptop), Debian GNU/Linux 7.0 (server), Mythbuntu 12.04 LTS (HTPC), Bodhi Linux 2.0 & Windows 7 Ultimate (test desktop), FreeBSD 9.1 (test server)

Last edited by SuperOscar : July 15th, 2012 at 01:19 PM.

July 15th, 2012, 08:55 PM

jepot

Registered User

Join Date: Dec 2008

Posts: 17

Time spent in forums: 5 h 17 m 23 sec
Reputation Power: 0

Thanks guys, all your solutions worked and fixed both problems.

List Matching, and outputting to text from multiple lists

Developer Shed Advertisers and Affiliates