[Python-ideas] Split, slice, join and return "syntax" for str

[Steven D'Aprano]

On Sun, Mar 04, 2018 at 12:11:16PM -0800, Michel Desmoulin wrote:

> But, first, they are not common enough so that it's hard to do:
> 
> spam = docs.python.org"
> eggs = 'wiki.' + '.'.join(spams.split('.')[1:])

In a more realistic case, the delimiter is not necessarily a constant, 
nor will you always want to replace the first item.

So you would be writing:

delimiter.join(
        spam.split(delimiter)[:n-1] + 
        ['wiki'] + spam.split(delimiter)[n+1:]
        )


Suddenly it's a lot less attractive to be typing out each time.

It is a good candidate for a helper function:

def replace_field(string, delimiter, position, new, start=0, end=None):
    fields = string[start:end].split(delimiter)
    fields[position] = new
    string = (string[:start] + delimiter.join(fields) 
              + ('' if end is None else string[end:]))
    return string

That's not the most efficient implementation, and it isn't thoroughly 
tested/debugged, but it ought to be good enough for casual use.

Personally, if this were available as a string method I think I'd use 
this quite frequently, certainly more often than I use some other string 
methods like str.partition.


> It's not that long to type, and certainly is not happening in every
> single script you do.

Speak for yourself :-)

No, not literally every script. (If that were the requirement to be a 
string method, strings would have no methods.) But I think it is common 
enough that I'd be happy for it to be a string method.


-- 
Steve