How to output multiple lists while looping through other input lists?

Question

For the following 2 input lists, I want different output lists based on the first one:

al = ["tr1", "tr2", "tr3"]
bl = ["tile1", "tile2", "tile3"]
newlist  = []

for a in al:
    for b in bl:
        c = a+b+"5"
        newlist.append(c)
print(newlist)

['tr1tile15', 'tr1tile25', 'tr1tile35', 'tr2tile15', 'tr2tile25', 'tr2tile35', 'tr3tile15', 'tr3tile25', 'tr3tile35']

Desired output:

newlist_tr1 = ['tr1tile15', 'tr1tile25', 'tr1tile35']
newlist_tr2 = ['tr2tile15', 'tr2tile25', 'tr2tile35']
newlist_tr3 = ['tr3tile15', 'tr3tile25', 'tr3tile35']

Working on Windows 10, Python 3.7.6.

azro · Accepted Answer · 2021-02-03 17:11:53Z

2

You need an intermediate list in the loop

al = ["tr1", "tr2", "tr3"]
bl = ["tile1", "tile2", "tile3"]
newlist = []

for a in al:
    tmp = []
    for b in bl:
        tmp.append(a + b + "5")
    newlist.append(tmp)

print(newlist) 
# [['tr1tile15', 'tr1tile25', 'tr1tile35'], 
   ['tr2tile15', 'tr2tile25', 'tr2tile35'], 
   ['tr3tile15', 'tr3tile25', 'tr3tile35']]

You can achieve the same with lists-comprehension

newlist = [[a + b + "5" for b in bl] for a in al]

edited Feb 3, 2021 at 17:11

answered Feb 1, 2021 at 17:54

azro

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3 Comments

delViento Over a year ago

thank you very much!!!!! How is that called? I checked in python tutorials about lists, but I couldn't find information on how to build those lists. Also, you are creating a list of lists, I guess, making complete independent lists is different

azro Over a year ago

@delViento this is called list-comprehension docs.python.org/3/tutorial/… . Also you can now think about acepting the answer, green tick, if it satisfies you ;)

delViento Over a year ago

Thank you! I upvoted it and forgot to accept

Stephan Kulla · Accepted Answer · 2021-02-01 17:57:01Z

0

al = ["tr1", "tr2", "tr3"]
bl = ["tile1", "tile2", "tile3"]

newlist = [[a + b + "5" for b in bl] for a in al]

Result:

[['tr1tile15', 'tr1tile25', 'tr1tile35'],
 ['tr2tile15', 'tr2tile25', 'tr2tile35'],
 ['tr3tile15', 'tr3tile25', 'tr3tile35']]

answered Feb 1, 2021 at 17:57

Stephan Kulla

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Comments

Mahesh · Accepted Answer · 2021-02-01 17:58:33Z

0

bl = ["tile1", "tile2", "tile3"]
newlist  = []


for a in al:
    for b in bl:
        c = a+b+"5"
        newlist.append(c)
    print(newlist)
    newlist  = []

['tr1tile15', 'tr1tile25', 'tr1tile35']
['tr2tile15', 'tr2tile25', 'tr2tile35']
['tr3tile15', 'tr3tile25', 'tr3tile35']```

answered Feb 1, 2021 at 17:58

Mahesh

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Comments

Ajay · Accepted Answer · 2021-02-03 17:29:02Z

0

from itertools import product

m=["".join(elem)+'5' for elem in list(product(al,bl))]

for i in al:
    newlist_i =m[:len(al)]

product(A, B) returns the same as ((x,y) for x in A for y in B).

answered Feb 3, 2021 at 17:29

Ajay

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