[Tutor] Replace a character by index

[Wayne]

Hi,

My question is more about style/timing than anything else.

In my program I'm taking a word and generating "blanks" in that word. For
example, the word cat could generate:
_at
c_t
ca_

I have two different ways I can put _ in the word:
word = 'cat'

''.join(list(word)[1] = '_')

and

# I'm not using a constant, but randomly generating where the blank appears
word[:1] + '_' + word[1+1:]

So, when I use the timeit module I get these results:

In [78]: timeit.Timer("''.join(list('foo'))").timeit()
Out[78]: 2.9940109252929688

In [80]: timeit.Timer("'foo'[:2]+'_'+'foo'[2+1:]").timeit()
Out[80]: 0.63733291625976562

Quite a significant difference.

So my question(s): Which method should I use/is more pythonic? Which method
do you/have you used? And the ubiquitous 'Why?'

Normally I would lean towards the first method because reassigning a value
in a list seems more natural than string concatenation. In this particular
application I'm not exactly worried about performance - on even an archaic
computer I don't think one would notice.

TIA for your input,
Wayne
-- 
To be considered stupid and to be told so is more painful than being called
gluttonous, mendacious, violent, lascivious, lazy, cowardly: every weakness,
every vice, has found its defenders, its rhetoric, its ennoblement and
exaltation, but stupidity hasn’t. - Primo Levi
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