Change value in cell using Python

[tiredofit]

I have this in the formula bar in cell J1 in Excel, which is a VLookup:

df1=xl("A1:I100", headers=True)
df2=xl("'Sheet2'!A1:O200", headers=True)

Left_join = df1.merge(df2,
                     left_on='MyField',
                     right_on= xl("'Sheet2'!O1"),
                     how = 'left')

res=Left_join

res=res[[xl("'Sheet2'!C1")]]

res=res.fillna('Not Found')

Now I just want to change the value in cell J1 (which is a header) from Output to Result.

I've tried adding this to the formula above:

res.replace("Output","Result")

but it doesn't change it.

What is wrong?

Thanks

 

[tiredofit]

SORTED:

res= res.rename(columns={'Output': 'Result'})