In Python3.8 and prior, you can type this in a shell session
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Python 3.8.2 (v3.8.2:7b3ab5921f, Feb 24 2020, 17:52:18) 
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license()" for more information.
>>> def square(x):
	s = x ** 2
	return s


In Python3.9, the input is terminated prematurely
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Python 3.9.0a6 (v3.9.0a6:bc1c8af8ef, Apr 27 2020, 17:05:28) 
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license()" for more information.
>>> def square(x):
	s = x ** 2             # <-- On first return, the statement evaluates
	
>>> 

>>> square(5)
25