Change first occurrence of character x in a string - how?

[MRAB]

On 2021-02-14 21:14, Chris Green wrote:
> What's the easiest way to change the first occurrence of a specified
> character in a string?
> 
> E.g. I want to change linux-raid.vger.kernel.org to
> linux-raid at vger.kernel.org, it's a fairly general requirement of
> needing to change '.' to '@'.
> 
> Alternatively is there an RE 'match' function that would test if
> linux-raid at vger.kernel.org matches linux-raid.vger.kernel.org? I don't
> really care if the '.' are all regarded as wild cards, the match will
> be accurate enough.
> 
Use the .replace method. Its 3rd argument is the maximum number of 
replacements, in this case 1:

 >>> s = 'linux-raid.vger.kernel.org'
 >>> s.replace('.', '@', 1)
'linux-raid at vger.kernel.org'