I have a below list.
['A_1', 'A_2', 'A_3', 'A_4', 'B_1','B_2', 'C_1', 'C_2', 'C_3']
I need the output in below format.
[['A_1', 'A_2', 'A_3', 'A_4'], ['B_1', 'B_2'], ['C_1', 'C_2', 'C_3']]
I am very new to Python, is there any way to achieve the above output that it would be really helpful.
This can be achieved directly with a dictionary combined with a loop：
category = {}
lst = ['A_1', 'A_2', 'A_3', 'A_4', 'B_1','B_2', 'C_1', 'C_2', 'C_3']
for item in lst:
prefix = item.split("_")[0] + "_" # Example of prefix values: A_, B_,...
if prefix not in category:
category[prefix] = [item]
else:
category[prefix].append(item)
print(list(category.values()))
# [['A_1', 'A_2', 'A_3', 'A_4'], ['B_1', 'B_2'], ['C_1', 'C_2', 'C_3']]
in on a dictionnary search in the keys ? Or is it because theres no str value that contains the prefix ?I provided a easily understandable way (but requires more lines than other advanced thecniques)
You can use dictionary, in particular, I used defaultdict here to set default value as a list ([]).
I grouped the list by first letter in a for loop, as follows:
from collections import defaultdict
l = ['A_1', 'A_2', 'A_3', 'A_4', 'B_1', 'B_2', 'C_1', 'C_2', 'C_3']
group = defaultdict(list)
for item in l:
first_letter = item[0] # saving items by first letter
group[first_letter].append(item)
result = list(group.values())
print(result)
# [['A_1', 'A_2', 'A_3', 'A_4'], ['B_1', 'B_2'], ['C_1', 'C_2', 'C_3']]
You can use itertools.groupby for that. This assumes that the input is sorted, as in your example.
from itertools import groupby
lst = ['A_1', 'A_2', 'A_3', 'A_4', 'B_1', 'B_2', 'C_1', 'C_2', 'C_3']
output = [list(g) for _, g in groupby(lst, key=lambda x: x[0])]
print(output) # [['A_1', 'A_2', 'A_3', 'A_4'], ['B_1', 'B_2'], ['C_1', 'C_2', 'C_3']]
If for some reason you don't want to use import but only use built-ins,
lst = ['A_1', 'A_2', 'A_3', 'A_4', 'B_1', 'B_2', 'C_1', 'C_2', 'C_3']
output = {}
for x in lst:
if x[0] in output:
output[x[0]].append(x)
else:
output[x[0]] = [x]
print(list(output.values()))
Note that with an input list of ['A_1', 'B_1', 'A_2'] the two approaches will result in different outputs.
Refer below code:
input = ['A_1', 'A_2', 'A_3', 'A_4', 'B_1', 'B_2', 'C_1', 'C_2', 'C_3']
Use below logic:
ls_a,ls_b,ls_c = [],[],[] # Declaring empty lists
for i in input:
if 'A' in i:
ls_a.append(i)
if 'B' in i:
ls_b.append(i)
if 'C' in i:
ls_c.append(i)
output = [ls_a,ls_b,ls_c]
print(output)
['A_1', 'B_1', 'A_2']?