Getting a string representation of a coordinate is best approached by treating the components (e.g., RA and Dec) separately. For example:
>>> from astropy.coordinates import ICRSCoordinates
>>> c = ICRSCoordinates(187.70592, 12.39112, unit=(u.degree, u.degree))
>>> str(c.ra) + ' ' + str(c.dec)
'187d42m21.31200s 12d23m28.03200s'
To get better control over the formatting, you can use the angles’ format method (see Working with Angles for more). For example:
>>> rahmsstr = c.ra.format(u.hour)
>>>> rahmsstr
'12h30m49.42080s'
>>> decdmsstr = c.dec.format(u.degree, alwayssign=True)
>>> decdmsstr
'+12d23m28.03200s'
>>> rahmsstr + ' ' + decdmsstr
'12h30m49.42080s +12d23m28.03200s'