Unable to read value for variable outside loop in python - python-3.x

Question

I am trying to create a list of dictionaries that contain lists of words at 'body' and 'summ' keys using spacy. I am also using BeautifulSoup since the actual data is raw html.
This i what I have so far
from pymongo import MongoClient
from bs4 import BeautifulSoup as bs
import spacy
import string
clt = MongoClient('localhost')
db1 = clt['mchack']
db2 = clt['clean_data']
nlp = spacy.load('en')
valid_shapes = ['X.X','X.X.','X.x','X.x.','x.x','x.x.','x.X','x.X.']
cake = list()
sent_x = list()
temp_b = list()
temp_s = list()
sent_y = list()
table = str.maketrans(dict.fromkeys(string.punctuation))
for item in db1.article.find().limit(1):
finale_doc = {}
x = bs(item['news']['article']['Body'], 'lxml')
y = bs(item['news']['article']['Summary'], 'lxml')
for content in x.find_all('p'):
v = content.text
v = v.translate(table)
sent_x.append(v)
body = ' '.join(sent_x)
for content in y.find_all('p'):
v = content.text
v = v.translate(table)
sent_y.append(v)
summ = ' '.join(sent_y)
b_nlp = nlp(body)
s_nlp = nlp(summ)
for token in b_nlp:
if token.is_alpha:
temp_b.append(token.text.lower())
elif token.shape_ in valid_shapes:
temp_b.append(token.text.lower())
elif token.pos_=='NUM':
temp_b.append('<NUM>')
elif token.pos_=="<SYM>":
temp_b.append('<SYM>')
for token in s_nlp:
if token.is_alpha:
temp_s.append(token.text.lower())
elif token.shape_ in valid_shapes:
temp_s.append(token.text.lower())
elif token.pos_=='NUM':
temp_s.append('<NUM>')
elif token.pos_=="<SYM>":
temp_s.append('<SYM>')
finale_doc.update({'body':temp_b,'summ':temp_s})
cake.append(finale_doc)
print(cake)
del sent_x[:]
del sent_y[:]
del temp_b[:]
del temp_s[:]
del finale_doc
print(cake)
The first print statement gives proper output
'summ': ['as', 'per', 'the', 'budget', 'estimates', 'we', 'are', 'going', 'to', 'spend', 'rs', '<NUM>', 'crore', 'in', 'the', 'next', 'year'],
'body': ['central', 'government', 'has', 'proposed', 'spendings', 'worth', 'over', 'rs', '<NUM>', 'crore', 'on', 'medical', 'and', 'cash', 'benefits', 'for', 'workers', 'and', 'family', 'members']}]
However, after emptying the lists sent_x, sent_y, temp_b and temp_s, the output comes:
[{'summ': [], 'body': []}]

Answer 1

You keep passing the references to temp_b and temp_s. That's why after emptying these lists cake's content also changes (values of the dictionary are the same objects as temp_b and temp_s)!
You simply need to make a copy before appending the finale_doc dict to cake list.
finale_doc.update({'body': list(temp_b), 'summ': list(temp_s)})

Answer 2

You should try creating a minimal reproducible version of this, as it would meet stack overflow guidelines and you would be likely to answer your own problem.
I think what you are asking is this:
How can I empty a list without changing other instances of that list?
I made some code and I think it should work:
items = []
contents = []
for value in (1, 2):
contents.append(value)
items.append(contents)
print(contents)
del contents[:]
print(items)
This prints [1], [2] like I want, but then it prints [[], []] instead of [[1], [2]].
Then I could answer your question:
Objects (including lists) are permanent, this won't work
Instead of modifying (adding to and then deleting) the same list, you probably want to create a new list inside the loop. You can verify this by looking at id(contents) and id(items[0]), etc., and see they are all the same list. You can even do contents.append(None); print(items) and see that you now have [None, None].
Try doing
for ...
contents = []
contents.append(value)
instead of
contents = []
for ...
del contents[:]
Edit: Another answer suggests making a copy of the values as you add them. This will work, but in your case I feel that making a copy and then nulling is unnecessarily complicated. This might be appropriate if you continued to add to the list.