Your implementation takes several lines of code only because of complex semantic of findall() which you want to preserve in findfirst(). Actually findall() is an equivalent of one of three expressions, depending on the number of capturing groups in the regular expression:

    [m[0] for m in finditer(...)]
    [m[1] for m in finditer(...)]
    [m.groups() for m in finditer(...)]

so findfirst() is an equivalent of one of three expressions:

    search(...)[0]
    search(...)[1]
    search(...).groups()

In real code the number of capturing groups in the regular expression you use is known statically, so you should not dispatch one of above variants at run time. You just use the appropriate one.

findall() is older interface. More modern, generator and object interface is finditer(). findall() was not deprecated and was not converted to returning an iterator because many old code uses it, and we do not want to break it.