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Facing trouble in creating sublists of a list

How to group a flat list of attributes into a nested lists?

My task is to create combinations, more like a Cartesian product for some attribute lines of a library file. I am currently facing the problem of grouping the same attributes(of course the adjacent parameters are different) as sublists of a list. Remember my input may contain a thousand lines of attributes , which I need to extract from a library file.
~~######################~~
Example input:
```
~~attr1 apple 1~~
~~attr1 banana 2~~
~~attr2 grapes 1~~
~~attr2 oranges 2~~
~~attr3 watermelon 0~~
```
~~######################~~
~~Example output:~~
~~```~~
~~[['attr1 apple 1','attr1 banana 2'], ['attr2 grapes 1','attr2 oranges 2'], ['attr3 watermelon 0']]~~
~~```~~
~~The result I am getting:~~
~~```~~
~~['attr1 apple 1','attr1 banana 2', 'attr2 grapes 1','attr2 oranges 2', 'attr3 watermelon 0']~~
~~```~~
~~Below is my code:~~
```
import re
# regex pattern definition
pattern = re.compile(r'attr\d+')
# Open the file for reading
with open(r"file path") as file:
# Initialize an empty list to store matching lines
matching_lines = []
# reading each line
for line in file:
# regex pattern match
if pattern.search(line):
# matching line append to the list
matching_lines.append(line.strip())
# Grouping the elements based on the regex pattern
#The required list
grouped_elements = []
#Temporary list for sublist grouping
current_group = []
for sentence in matching_lines:
if pattern.search(sentence):
current_group.append(sentence)
else:
if current_group:
grouped_elements.append(current_group)
current_group = [sentence]
if current_group:
grouped_elements.append(current_group)
# Print the grouped elements
for group in grouped_elements:
print(group)
~~```~~

I have a flat list where each item is the key and value for an attribute. I want to transform this into a nested list where each attribute is a sublist.
Example input:
```
[
"attr1 apple 1",
"attr1 banana 2",
"attr2 grapes 1",
"attr2 oranges 2",
"attr3 watermelon 0"
]
```
The output should be:
```
[
[
"attr1 apple 1",
"attr1 banana 2",
],
[
"attr2 grapes 1",
"attr2 oranges 2",
],
[
"attr3 watermelon 0"
]
]
```
---------------------
I tried this program, but the result is incorrect.
```
import re
# regex pattern definition
pattern = re.compile(r'attr\d+')
# Open the file for reading
with open(r"file path") as file:
# Initialize an empty list to store matching lines
matching_lines = []
# reading each line
for line in file:
# regex pattern match
if pattern.search(line):
# matching line append to the list
matching_lines.append(line.strip())
# Grouping the elements based on the regex pattern
#The required list
grouped_elements = []
#Temporary list for sublist grouping
current_group = []
for sentence in matching_lines:
if pattern.search(sentence):
current_group.append(sentence)
else:
if current_group:
grouped_elements.append(current_group)
current_group = [sentence]
if current_group:
grouped_elements.append(current_group)
# Print the grouped elements
for group in grouped_elements:
print(group)
```
I am getting this output:
```
[
'attr1 apple 1',
'attr1 banana 2',
'attr2 grapes 1',
'attr2 oranges 2',
'attr3 watermelon 0'
]
```

python list sublist

python grouping list

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