Useful Functions: String Functions

Question

If I have to change only a certain part of the string to uppercase letters. How will I do it?
I tried making only 'hi' to HI using upper() in 'hi sololearn' but couldn't get the right code.
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In [45]: x = 'hi sololearn'

In [46]: print(x.upper())
HI SOLOLEARN

In [47]: print(x[0].upper(),x[1].upper())
H I
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Answer 1

I had a little fun here:
https://code.sololearn.com/cLZcRRg56c2F/?ref=app