import re
s = 'blahblah "key":"value","TargetCRS": "Target","TargetCRScode": "vertical Code","zzz": "aaaa" sadzxc "sss"'
r = re.compile(r'''"key"\s*:\s*"([^"]*)"''')
match = r.search(s)
if match:
print match.group(1)
aW1wb3J0IHJlCgpzID0gJ2JsYWhibGFoICJrZXkiOiJ2YWx1ZSIsIlRhcmdldENSUyI6ICJUYXJnZXQiLCJUYXJnZXRDUlNjb2RlIjogInZlcnRpY2FsIENvZGUiLCJ6enoiOiAiYWFhYSIgc2FkenhjICJzc3MiJwpyID0gcmUuY29tcGlsZShyJycnImtleSJccyo6XHMqIihbXiJdKikiJycnKQoKbWF0Y2ggPSByLnNlYXJjaChzKQppZiBtYXRjaDoKCXByaW50IG1hdGNoLmdyb3VwKDEp