如何使用不同大小的列表创建 Python 字典？

Question

I have been learning to manipulate strings with regex, but have run into a problem formatting a dictionary with some data I am working with. Here is a simplified version of the code I am struggling with:

import re

line=">sp|A|PE=3 SV=1 IDMANTTI >sp|B|PE=3 SV=1 EVPFYPKA >sp|C| PE=3 SV=2 QRWLFNYSGNISN"

NGly_Sites=[]
protein_list=[]

p_and_a=re.findall(r'sp\|(\w+)\|.+?SV=\d\s([A-Z]+)', line) 
for protein, amino in p_and_a:
    print(protein, amino)
    protein_list.append(protein)
    NGly_Sites=re.findall(r'N[^P][ST][^P]', amino)
    print(NGly_Sites)
Sites={k:v for k,v in zip(protein_list, NGly_Sites)}
print(Sites)

And it prints:

A IDMANTTI
['NTTI']
B EVPFYPKA
[]
C QRWLFNYSGNISN
['NYSG', 'NISN']
{'A': 'NYSG', 'B': 'NISN'

I am trying to match up items I have named "protein" with the resulting sequences I have found using the .findall() function in python. Essentially I am wanting to do the following:

{'A':['NTTI'],'C':['NYSG','NISN']}

I do not understand why the objects found using the .findall() function that are being placed into the dictionary are being done so under all the keys ('A', 'B', 'C') rather then their specific key or why I can't seem to attach a list of the objects found using .findall() under one key. I'm sure this is just something to do with syntax, but I've experimented with {k:v for k,v in zip(list1,list2)} which was how I was told to make a dictionary with two lists, and I can't seem to figure out how to get it to insert a list within a list. How can I go about doing this?

Answer 1

You can use a list comprehension to build a complete protein list of tuple pairs, then a dict comprehension to filter out empty list values. This could be done in a single dict comprehension, but breaking it into two steps is a little bit clearer and saves an awkward extra call to findall for extracting the protein sequences.

import re

line = ">sp|A|PE=3 SV=1 IDMANTTI >sp|B|PE=3 SV=1 EVPFYPKA >sp|C| PE=3 SV=2 QRWLFNYSGNISN"
protein_pattern = r"sp\|(\w+)\|.+?SV=\d\s([A-Z]+)"
sites_pattern = r"N[^P][ST][^P]"

all_proteins = [
    (k, re.findall(sites_pattern, v)) 
    for k, v in re.findall(protein_pattern, line)
]
sites = {k: v for k, v in all_proteins if v}

print(sites) # => {'A': ['NTTI'], 'C': ['NYSG', 'NISN']}

Answer 2

import re

line=">sp|A|PE=3 SV=1 IDMANTTI >sp|B|PE=3 SV=1 EVPFYPKA >sp|C| PE=3 SV=2 QRWLFNYSGNISN"

p_and_a=re.findall(r'sp\|(\w+)\|.+?SV=\d\s([A-Z]+)', line) 

sites =  { protein : re.findall(r'N[^P][ST][^P]', amino)  for protein, amino in p_and_a }

print(sites)

# {'A': ['NTTI'], 'B': [], 'C': ['NYSG', 'NISN']}