How to join array more than one array in python

Question

I have 4 arrays like this:

temp1 = ['a' , 'b' , 'c']
temp2 = ['d' , 'e' ,'' ]
temp3 = ['f']
temp4 = ['g']

I want output:

adfg
aefg
afg
bdfg
befg
bfg
cdfg
cefg
cfg

and I solved it using following:

temp1 = ['a' , 'b' , 'c']
temp2 = ['d' , 'e' ,'' ]
temp3 = ['f']
temp4 = ['g']
for list_1 in temp1:
    for list_2 in temp2:
        for list_3 in temp3:
            for list_4 in temp4:
                temp_list = ''
                if list_1: temp_list += list_1
                if list_2: temp_list += list_2
                if list_3: temp_list += list_3
                if list_4: temp_list += list_4
                print "%s " %(temp_list)

but I think my code isn't efficient.

How to make good algorithm and make it efficient.

and how about if temp3 is null for example :

temp1 = ['a' , 'b' , 'c']
temp2 = ['d' , 'e' ,'' ]
temp3 = []
temp4 = ['g']

AKS · Accepted Answer · 2016-06-08 08:55:59Z

5

You can use itertools.product:

>>> from itertools import product
>>> result = product(temp1, temp2, temp3, temp4)
>>> ["".join(item) for item in result]
['adfg', 'aefg', 'afg', 'bdfg', 'befg', 'bfg', 'cdfg', 'cefg', 'cfg']

UPDATE:

If temp3 is empty as in the updated question, I think you would like to skip it while generating the results. If that's the case, you can only use the list which have some items:

>>> input_lists = [arr for arr in (temp1, temp2, temp3, temp4) if arr]
>>> result = product(*input_lists)
>>> ["".join(item) for item in result]
['adg', 'aeg', 'ag', 'bdg', 'beg', 'bg', 'cdg', 'ceg', 'cg']

edited Jun 8, 2016 at 8:55

answered Jun 8, 2016 at 5:51

AKS

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5 Comments

sohainewbie Over a year ago

how about if the array null ??? temp1 = ['a' , 'b' , 'c'] temp2 = ['d' , 'e' ,'' ] temp3 = [] temp4 = ['g'] output will be []

AKS Over a year ago

Yes, it will return [] and that is the expected behavior of this function. What do you expect the output to be if there is an empty array?

AKS Over a year ago

I updated the answer in case of empty temp3 if that's the output which is expected.

sohainewbie Over a year ago

yes , i think it must be filter with 'if' but thank you

AKS Over a year ago

The answer you have accepted would result in [] if temp3 is empty.

Abdul Fatir · Accepted Answer · 2016-06-08 05:52:53Z

1

Use itertools.product().

>>> import itertools
>>> result = [''.join(i) for i in itertools.product(temp1,temp2,temp3,temp4)]
>>> result
['adfg', 'aefg', 'afg', 'bdfg', 'befg', 'bfg', 'cdfg', 'cefg', 'cfg']

answered Jun 8, 2016 at 5:52

Abdul Fatir

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Comments

Abhirath Mahipal · Accepted Answer · 2016-06-08 05:58:36Z

0

Use Python Comprehensions. They are cleaner and more elegant.

temp1 = ['a' , 'b' , 'c']
temp2 = ['d' , 'e' ,'' ]
temp3 = ['f']
temp4 = ['g']

templist = [i+j+k+l for i in temp1 for j in temp2 for k in temp3 for l in temp4] 
# Result - ['adfg', 'aefg', 'afg', 'bdfg', 'befg', 'bfg', 'cdfg', 'cefg', 'cfg']

i+j+k+l helps to concatenate strings. Whenever you intend to use items from lists, try using comprehensions.

You can check this out http://www.pythonforbeginners.com/basics/list-comprehensions-in-python

edited Jun 8, 2016 at 5:58

answered Jun 8, 2016 at 5:49

Abhirath Mahipal

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