Python joining an array into a single line with a new line for every two elements

Question

I have an array with 8 items like the below array (dummy data), I only want the first 6 items. I can't seem to get .join correct.

["MR_L: ", 20, "Time: ", "10:00", "Email: ", "Testing@test", "Telephone: ", 0002411212]

I want the out come to be in a string:

"MR_L: 20
Time: 10:00
Email: Testing@test"

I've tried a for loop like: for index in range (0, 5, 2) then use index -1. It is important this is all in one string as I am using a function that can only take a single string as an argument. When I use join I get a memory error.

The longest the array will be is 22 items, it will join 18 and ignore the final two pairs. The name field can be 34 characters long as a string, the biggest integer is 16 digits long. — OttoLuck, Dec 23 '22 at 16:25
That's not a valid Python list due to the leading zeroes for the last value. Also... "memory error"? — DarkKnight, Dec 23 '22 at 16:26
Okay, so it's not gigabytes in size. Can you please show the exact and complete error message with traceback? — mkrieger1, Dec 23 '22 at 16:26
`8 - 6 = 2`, `22 - 18 = 4`. So what's your rule of changing ratio? — RomanPerekhrest, Dec 23 '22 at 16:29
File "c:\Users\red\OneDrive - ---\---\---\---\app.py", line 150, in Get_Da outPut = outPut.join(allItems[i-1] + allItems[i] + "\n") MemoryError — OttoLuck, Dec 23 '22 at 16:31
@OttoLuck This is a guess but if your value in *i* is massive then I suppose that *might* induce a memory error. Unfortunately you've chosen not to share your code so its hard to tell — DarkKnight, Dec 23 '22 at 16:39
So is your question how you can resolve the memory error or if your code was correct if you did not get a memory error? — mkrieger1, Dec 23 '22 at 16:39

score 2 · Answer 1 · answered Dec 23 '22 at 16:26

2

There are various ways to do it. One way is like this:

data = ["MR_L: ", 20, "Time: ", "10:00", "Email: ", "Testing@test", "Telephone: ", 2411212]

# STEP 1. convert all items to str type and put \n (newline) to every second items.
str_data = [str(item) if i % 2 == 0 else str(item)+"\n" for i, item in enumerate(data)]
print(str_data)
# ['MR_L: ', '20\n', 'Time: ', '10:00\n', 'Email: ', 'Testing@test\n', 'Telephone: ', '2411212\n']

# STEP 2. combine the first six items 
result = "".join(str_data[:6])[:-1] # [:-1] to remove last "\n"
print(result)
"""
MR_L: 20
Time: 10:00
Email: Testing@test
"""

answered Dec 23 '22 at 16:26

Park

2,446
1
16
25

This just saves 3 items of the 18 that I want – OttoLuck Dec 23 '22 at 16:43
@OttoLuck 18? I quote from your question "I only want the first 6 items" – DarkKnight Dec 23 '22 at 16:47

DarkKnight · Accepted Answer · 2022-12-23T16:53:01.127

2

If the integer value(s) in your list are valid then you could do this:

mylist = ["MR_L: ", 20, "Time: ", "10:00", "Email: ", "Testing@test", "Telephone: ", 2411212]

parts = []

for i in range(0, min(6, len(mylist)), 2):
    parts.append('{}{}'.format(*mylist[i:i+2]))

print(*parts, sep='\n')

Output:

MR_L: 20
Time: 10:00
Email: Testing@test

edited Dec 23 '22 at 16:53

answered Dec 23 '22 at 16:30

DarkKnight

19,739
3
6
22

I tried this although instead of print used: outPut = outPut + ('\n'.join(parts)). It repeats data constantly? – OttoLuck Dec 23 '22 at 16:40
@OttoLuck Why don't you try it in the way I've written it then ask yourself why, when you change the code, it goes wrong – DarkKnight Dec 23 '22 at 16:42
This worked with the original edit for my use case. – OttoLuck Dec 23 '22 at 16:51

score 1 · Answer 3 · answered Dec 23 '22 at 16:47

Consider using the pairwise() implementation from Iterating over every two elements of a list to solve that part of your problem.

Next you can convert your pairs into strings:

[f"{k}{v}" for k, v in pairwise(allItems)]

Omit the last pair (two elements):

[f"{k}{v}" for k, v in pairwise(allItems[:-2])]

And join with newlines:

"\n".join(f"{k}{v}" for k, v in pairwise(allItems[:-2]))

score 1 · Answer 4 · answered Dec 23 '22 at 16:53

I think your data suggests a pairwise grouping:

from itertools import pairwise

data = ["MR_L: ", 20, "Time: ", "10:00", "Email: ", "Testing@test", "Telephone: ", 2411212]

# group in pairs [["MR_L: ", 20], ...]
pairs = pairwise(data) # returns an iterable

# you then join pairs (you need 3 pairs for 6 items)
"\n".join(f"{k}{v}" for k, v in list(pairs)[:3])

Arifa Chan · Answer 5 · 2022-12-23T17:50:14.063

0

You can try using generator expression and zip of the list from index 0 to length of the list -2 with 2 step and from index 1 likewise:

mylist = ["MR_L: ", 20, "Time: ", "10:00", "Email: ", "Testing@test", "Telephone: ", 2411212]

outPut = lambda lst: '\n'.join(f'{a}{b}' for a,b in zip(lst[:-2:2],lst[1::2]))

print(outPut(mylist))

# MR_L: 20
# Time: 10:00
# Email: Testing@test

edited Dec 23 '22 at 17:50

answered Dec 23 '22 at 17:44

Arifa Chan

947
2
6
23

Python joining an array into a single line with a new line for every two elements

5 Answers5