Python: List of sublists, write sublists without brackets

Question

I have a List that is x values long. The list is broken up into different length sublists.I then take these sublists and write them to an output file. Is there a way to print the sublists without the brackets.

Edited to clarfiy:

The actual list is 300 sublists long with 12250 elements in it, and changes with each senario I run. Obviously, this is simplified. Let me change a few things and see if that changes the answers.

i.e.

List=[[1, 2, 3], [4, 5, 6, 7], [8, 9, 10, 11, 12, 15]]

where the output is:

[1, 2, 3]
[4, 5, 6, 7]
[8, 9, 10, 11, 12, 15]

but I want

1, 2, 3
4, 5, 6, 7
8, 9, 10, 11, 12, 15

I want this output in a new variable, say ListMod, so then I can use ListMod in a seperate function to write a file. The file also calls 2 other lists, Time and Size, where Size designates the length of the line in ListMod.

How much does that modify your answers?

Solution 1

First, the answer:

file.write(','.join(map(repr, List))

Your actual code can't possibly be writing what you claim it is, for multiple reasons:

• A file's write method will give you a TypeError if you give it a list, not print it out. You have to call str or repr on the list to get something you can write.
• Calling str or repr on a list puts spaces after the commas, as well as brackets.
• You've got at least one SyntaxError in your code that would prevent you even getting that far.

So, I have to guess what you're actually doing before I can explain how to fix it. Maybe something like this:

file.write(str(List))

If so, the __str__ method of a list is effectively:

'[' + ', '.join(map(repr, self)) + ']'

You want this without the brackets and without the spaces, so it's:

','.join(map(repr, self))

Solution 2

Your output format appears to be CSV. If the actual data is as simple as in the example provided, then you can just use python's csv writer:

import csv
with open('/tmp/myfile.txt', 'w') as f:
    csv_writer = csv.writer(f)
    csv_writer.writerows(List)

Solution 3

If you're on Python 3.x or 2.6 onwards and don't mind using print as a function:

from __future__ import print_function # ignore if on py 3.x

for line in List:
    print(*line, sep=',', file=file)