python group strings in lists

Question

I have two lists with the same len.

list1=[0, 1, 1, 1, 0, 0, 0, 1]
list2=['ATT', 'TTC', 'TCC', 'CCC', 'CCA', 'CAA', 'AAA', 'AAG']

Note:

1). The number of elements in each list varies, but the two lists always have the same len.

2). list1 only contains integers 0, or 1. It can only contain 0s, only contain 1s, or contain both 0s and 1s.

3). list2 only contains strings with the same length, also for each string k (k is a index >0), list2[k][:-1]=list2[k-1][1:], meaning that if k=2, list[k]='TCC', list[k][:-1]='TC', list[k-1]='TTC', list[k-1][1:]='TC'. Thus, list2[k][:-1]=list2[k-1][1:].

I want to group the strings in list2 based on their corresponding elements in list1 (corresponding: elements in list1 and list2 sharing the same index). If list1[n]==1, then list2[n-1]+list2[n][-1]. If list1[n]==0, and list1[n+1]==0, do nothing.

e.g. the corresponding string of the first integer 1 in list2 is 'TTC', then 'ATT', and 'TTC' become 'ATTC'. The corresponding string of the second integer 1 in list2 is 'TCC', then 'ATTC' (Note; already combined), and 'TCC' become 'ATTCC'. Then list1[3]==1, 'ATTCC' and 'CCC' become 'ATTCCC'. list1[7]==1, then 'AAG' ('AAG'=list2[7]) needs to be grouped with its previous string, 'AAA', the two become 'AAAG'. The only condition that you do nothing is when n=0, and n+1=0. That's why, list1[4]==0, and list1[4+1]==0, 'CCA' stays the same. list1[5]==0, and list1[5+1]==0, then list2[5]='CAA' remains unchanged.

After transformation, This is the output I want. newlist2=['ATTCCC', 'CCA', 'CAA', 'AAAG']

Obviously the code is not correct.

for i in range(1, len(list1)):
    if list1[i]==1:
        newlist2[i-1]+newlist2[i][-1]  
    else:
        do nothing

What happens when list1[n]==0, but list1[n+1]!=0 (not equal zero)? — Hai Vu
– Hai Vu, Commented Mar 11, 2018 at 2:04
e.g. n=6, list1[6]==0, but list1[6+1]==1, then list2[6+1]='AAG', 'AAG' needs to be combined with 'AAA', (list2[6]). The idea is as long as list1[n]=1, regardless of what list1[n-1] is, 0 or 1, list2[n] needs to be combined with its previous string, note that the previous string might already combined with the previous previous string, if this makes sense, like in the example I gave above, the way 'ATTCCC' was produced. — JY078
– JY078, Commented Mar 11, 2018 at 2:13

user3483203 · Accepted Answer · 2018-03-11 02:02:56Z

2

Is this what you want?:

list1=[0, 1, 1, 1, 0, 0, 0, 1]
list2=['ATT', 'TTC', 'TCC', 'CCC', 'CCA', 'CAA', 'AAA', 'AAG']

indices = []
for i in range(1, len(list1)):
    if list1[i]==1:
        list2[i] = list2[i-1]+list2[i][-1]
        indices.append(i-1)


list2 = [list2[i] for i in range(len(list2)) if i not in indices]
print(list2)

Output:

['ATTCCC', 'CCA', 'CAA', 'AAAG']

I loop through your list, apply your method, and keep track of which indices I need to remove at the end, then I create a new list without the unnecessary indices.

answered Mar 11, 2018 at 2:02

user3483203

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Ajax1234 · Accepted Answer · 2018-03-11 02:05:43Z

2

You can use itertools.groupby with functools.reduce:

import itertools
import functools
list1=[0, 1, 1, 1, 0, 0, 0, 1]
list2=['ATT', 'TTC', 'TCC', 'CCC', 'CCA', 'CAA', 'AAA', 'AAG']
d = [[a, [h for _, h in b]] for a, b in itertools.groupby(zip(list1, list2), key=lambda x:x[0])]
final_results = [i for b in filter(None, [[functools.reduce(lambda x, y:x+y[-1], [d[i-1][-1][-1]]+d[i][-1])] if d[i][0] else d[i][-1][:-1] for i in range(len(d))]) for i in b]

Output:

['ATTCCC', 'CCA', 'CAA', 'AAAG']

edited Mar 11, 2018 at 2:05

answered Mar 11, 2018 at 1:37

Ajax1234

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3 Comments

Ajax1234 Over a year ago

@JY078 Can you clarify your logic for how to achieve ['ATTCCC', 'CCA', 'CAA', 'AAAG']? By strictly following the guideline you posted, ['ATTC', 'TTCC', 'TCCC', 'AAAG'] is the resulted output.

JY078 Over a year ago

1). if n=1, then you combine list2[n] with list2[n-1], so 'ATT' and 'TTC' become 'ATTC', then 'ATTC' and 'TCC' become 'ATTCC', then 'ATTCC' and 'CCC' become 'ATTCCC'. 'CCA', and 'CAA' stay the same, because n=0, also, n+1=0. Finally, 'AAA', and 'AAG' become 'AAAG', because 'AAG' in list1 is a 1, then 'AAG' needs to be combined with its previous string, 'AAA'.

Ajax1234 Over a year ago

@JY078 Thank you for the explanation. Please see my recent edit.

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