I want to check if something is in/not in a nested list

I hope you can help look at the code

sheros=[['Groot',23,34,35],['Rocket',45,56,67]]

print(sheros)
newname=input('what is your name? ' )
newstat=int(input('what is the new stat? ' ))

listlength=len(sheros)

while listlength!=0:
    if sheros[listlength-1][0]==newname:
        sheros[listlength-1][3]=sheros[listlength-1][2]
        sheros[listlength-1][2]=sheros[listlength-1][1]
        sheros[listlength-1][1]=newstat
        listlength-=1
    else:
        listlength-=1

#this is the part doing my head in!
if newname in sheros[]:
    print('already here')
else:
    sheros+=[[newname,newstat,0,0]]
print('added')

print(sheros)

I want it so that if the named person is already in the list it adds their new stat to the list of 3 and pushed out the oldest one (got that sorted in the while loop) but I then want to add the person to the end of the nested list if they don't appear yet (new entry), see the bit that says #this is the part doing my head in!

Is it too late, have I had too much gin?

Please help my brain hurts

Ross