import re
suchmuster="7sc"
text="""Row9: invdec, 7sc. Repeat 2x
Row10-Row11: 16sc
Stuff the arms from time to time, not very
tightly.
Row12: invdec, 6sc. Repeat 2x (14)
Row13-Row15: 14sc
Row16: invdec, 5sc. Repeat 2x (12)
Row17-Row19: 12sc
Row20: 6invdec (6)
Fix and leave the thread to sew the arms to the
body."""
gefunden = re.findall(suchmuster, text)
if gefunden:
                for i in gefunden:
                                print(i, "wurde gefunden",)
else:
                print ("Nix gefunden")

text.replace('7sc','7 fM')
print (text)