CODEWITHSUNDEEP
python
ayansalt2
ayansalt2

Reputation: 175

concatenate list item with previous item

I want to concatenate one item with the previous one if the item doesnt start with a digit

For example:

l = ["1. first paragraph", "2. second paragraph", "end of second paragraph", "3. third paragraph"]

result = []
curr_str = ""
for item in l:
    curr_str += item
    if not item[0].isdigit():
        result.append(curr_str)
        curr_str = ""

What I want

result = ["1. first paragraph", "2. second paragraphend of second paragraph", "3. third paragraph"]

What I have

result=["1. first paragraph2. second paragraphend of second paragraph"]

Upvotes: 3

Views: 328

Answers (5)

Tim Biegeleisen
Tim Biegeleisen

Reputation: 520978

One approach might be to join the list together as a single string, then split by whitespace followed by a numeric paragraph header:

import re

l = ["1. first paragraph", "2. second paragraph", "end of second paragraph", "3. third paragraph"]
inp = ' '.join(l)
paragraphs = re.split(r'\s+(?=\d+\.)', inp)
print(paragraphs)

This prints:

['1. first paragraph',
 '2. second paragraph end of second paragraph',
 '3. third paragraph']

Upvotes: 2

python_user
python_user

Reputation: 7083

You can use negative indexing to get what you want

l = ["1. first paragraph", "2. second paragraph", "end of second paragraph", "3. third paragraph"]
res = []
for i in l:
    if i[0].isdigit():
        res.append(i)
    else:
        res[-1] = res[-1] + i
print(res)

Output

['1. first paragraph', '2. second paragraphend of second paragraph', '3. third paragraph']

Note:

This will not work if your first element does not start with a number.

To make it work for that as well you need to change the if condition like so, if not res or i[0].isdigit():, if the list is empty or if first character is a digit.

Upvotes: 3

KHEIREDDINE ATTALA
KHEIREDDINE ATTALA

Reputation: 1

There you go

l = ["1. first paragraph", "2. second paragraph", "end of second paragraph", "3. third paragraph"]

result = []
curr_str = l[0]
for item in l[1:]:
    if item[0].isdigit():
        result.append(curr_str)
        curr_str = item
    else:
        curr_str+=item
result.append(curr_str)

This will work. I cannot really comment on your solution since I did not understand the though process behind it and started over. If you have any questions feel free

Upvotes: 0

Leonardo Scotti
Leonardo Scotti

Reputation: 1080

CODE

to concatenate all elements in a list you hev to use "".join(list), but in your case it have to be more selective, so we can use list comprehension:

l = ["1. first paragraph", "2. second paragraph", "end of second paragraph", "3. third paragraph"]

import re
result = [elem for elem in l if re.match('^\d.*$', elem)]
result = "\n".join(result)
print(result)

output:

1. first paragraph
2. second paragraph
3. third paragraph

EXPLAINATION

first step:

['1. first paragraph2. second paragraph3. third paragraph']

using list comprehension and regex i filter the values inside your input list and get a list containing only string beginning with digits

output:

['1. first paragraph', '2. second paragraph', '3. third paragraph']

second step:

result = ["\n".join(result)]

using the join builtin string method i concatenate your list item

Upvotes: 0

Barmar
Barmar

Reputation: 780818

You need to check whether the current item begins with a digit before you concatenate it to curr_str.

And at the end of the loop you need to check whether curr_str contains anything, so you can append the final items to the list.

l = ["1. first paragraph", "2. second paragraph", "end of second paragraph", "3. third paragraph"]

result = []
curr_str = ""
for item in l:
    if item[0].isdigit():
        if curr_str:
            result.append(curr_str)
            curr_str = ""
    curr_str += item
if curr_str:
    result.append(curr_str)

print(result)

Upvotes: 0

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