Full left and right "separator".join(L)

Ideas
1

Hi,
Quite often in the last years, I’ve seen situations in which we would need !a!b!c! as output from a list L = ['a', 'b', 'c'], here with separator='!', but it could be with any separator.

I’ve seen people using:

  1. separator + separator.join(L) + separator

  2. separator.join([""] + L + [""])

Proposal: what do you think about

  • separator.join(L) give a!b!c as usual
  • separator.join(L, prefix=True) give !a!b!c
  • separator.join(L, suffix=True) give a!b!c!
  • separator.join(L, prefix=True, suffix=True) give !a!b!c!

or something similar (with another names) to have cleaner code and avoid the repetition of separator?

2

It looks pretty niche. In most cases prefix and suffix are different and differ from separator.

I would write

'!%s!' % '!'.join(L)

It is more clear what prefix and suffix are used, and it is easy to change prefix and suffix.

3

you could also double-up the joins:

"!".join("abc").join("!!")
# '!a!b!c!'

Or write a helper function:

def wrap(inside, outside):
    return inside.join([outside, outside])