Replace only the ending of a string

Question

It irks me not to be able to do the following in a single line. I've a feeling that it can be done through list comprehension, but how?

given_string = "first.second.third.None"
string_splitted = given_string.split('.')
string_splitted[-1] = "fourth"
given_string = ".".join(string_splitted)

Please note that the number of dots (.) in the given_string is constant (3). So i always want to replace the fourth fragment of the string.

You *can* do this in one line, but it's not pretty. What's wrong with what you have there? Putting that in a function would be a better approach than a comprehension. — sytech, Dec 11 '18 at 19:40
I'm doing a very simple thing in 3 lines and i've a feeling it can be reduced. — Jai Sharma, Dec 11 '18 at 19:41
`".".join("first.second.third.None".split(".")[0:3] + ["fourth"])` — John Gordon, Dec 11 '18 at 19:44
@JoranBeasley i only want the replacement to happen at the end of the string. Your suggestion would replace it anywhere. — Jai Sharma, Dec 11 '18 at 19:50
nope ... only from the last period https://repl.it/repls/RunnyIntentProspect — Joran Beasley, Dec 11 '18 at 19:52

score 4 · Answer 1 · answered Dec 11 '18 at 19:52

4

It seems like you should be able to do this without splitting into an array. Find the last . and slice to there:

> given_string = "first.second.third.None"
> given_string[:given_string.rfind('.')] + '.fourth'

'first.second.third.fourth'

answered Dec 11 '18 at 19:52

Mark

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beat me to it!! – Paritosh Singh Dec 11 '18 at 19:53
Only 30 seconds @ParitoshSingh! – Mark Dec 11 '18 at 19:54
I wonder which one is more readable between this and the one Vasilis G. suggested. – Jai Sharma Dec 11 '18 at 19:58

score 2 · Accepted Answer · answered Dec 11 '18 at 19:42

2

You could try this:

given_string = "first.second.third.None"
given_string = ".".join(given_string.split('.')[:-1] + ["fourth"])
print(given_string)

Output:

first.second.third.fourth

answered Dec 11 '18 at 19:42

Vasilis G.

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score 2 · Answer 3 · answered Dec 11 '18 at 19:47

2

Try this one liner:-

print (".".join(given_string.split(".")[:-1]+["Fourth"]))

Output:

first.second.third.Fourth

answered Dec 11 '18 at 19:47

nandal

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score 0 · Answer 4 · answered Dec 11 '18 at 19:55

0

You could use rsplit. This would work no matter how many dots precede the last split

given_string = "first.second.third.None"
string_splitted = given_string.rsplit('.', 1)[0] + '.fourth'

print(string_splitted)
first.second.third.fourth

answered Dec 11 '18 at 19:55

Andrew

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score 0 · Answer 5 · answered Dec 11 '18 at 19:56

my_string = "first.second.third.None"
my_sub = re.sub(r'((\w+\.){3})(\w+)', r'\1fourth', my_string)
print(my_sub)
first.second.third.fourth

A good explanation of this style is here: How to find and replace nth occurence of word in a sentence using python regular expression?

Replace only the ending of a string

5 Answers5