how replace the word at a position in string with _and later use the previous word...plz answer fast

Answer 1

a = 'abc'
print(a.replace('c','C'))

output : abC

Answer 2

By copying his content in other variable

Answer 3

but this will replace word...wholly..how to use previous word again

Answer 4

a='abc'
b=a
then replace value in string a