如何使用python检测列表中的不同元素并从中创建新列表（查找）

Question

To send an e-mail element by element I need to first detect different elements in list and then create new lists from them.

Does anyone can help me about the problem below ?

The list that I mentioned is also interrelated with another one.

I have:

list_I = [123, 453, 444, 555, 567, ...]

list_II = [A , A, B, C, B, ....]

What I hope to get is:

New_list_I = [123, 453]

New_list_I_a = [A, A]

New_list_II = [444,567]

New_list_II_a = [B, B]

New_list_III = [555]

New_list_III_a = [C]

Answer 1

One way would be to create a dictionary from the two lists:

from collections import defaultdict
d = defaultdict(list)
for k,v in zip(list_2, list_1):
    d[k].append(v)

# defaultdict(list, {'A': [123, 453], 'B': [444, 567], 'C': [555]})

And then obtain the specified output from the dictionary using a list comprehension.

[[[k for _ in range(len(v))], v] for k,v in d.items()]
# [[['A', 'A'], [123, 453]], [['B', 'B'], [444, 567]], [['C'], [555]]]

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Note that a nested list structure is much easier to handle and to work with than rather a series of lists created dynamically. Note that from this result you can select each resulting sublist using Basic Slicing and Indexing

Answer 2

Why not just create a dict out of those two lists with a key,value and then sort on the basis of value:

list_I = [123, 453, 444, 555, 567]
list_II = ['A' , 'A', 'B', 'C', 'B']

res = dict(zip(list_I, list_II))
print(sorted(res.items(), key=lambda x:x[1]))

OUTPUT :

[(123, 'A'), (453, 'A'), (444, 'B'), (567, 'B'), (555, 'C')]