How to change a string into uppercase?

How can I convert a string into uppercase in Python?

When I tried to research the problem, I found something about string.ascii_uppercase, but it couldn't solve the problem:

>>> s = 'sdsd'
>>> s.ascii_uppercase
Traceback (most recent call last):
  File "", line 1, in 
AttributeError: 'str' object has no attribute 'ascii_uppercase'

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_{See How do I lowercase a string in Python? for the opposite.}