Remember, variables are just names of things. Things can be anything – integers, strings, even functions. Let’s play around with some variables, renaming them, and changing their value. Then we’ll predict what they output. What would the following output in Python?
>>> f = min >>> def f(x): ... return x + 1 ... >>> max = f >>> f, min = min, f >>> min(4) #1 >>> max(4) #2
The tricky part here is the line:
>>> f, min = min, f
In Python, we always evaluate the right side of an assignment before the left. In this case, we evaluate both the function
min and the function
f. We keep track of what those two variables are pointing to, then we reassign them. In this case,
f now points to where
min used to point to and
min now points to where
f points to. So, when we call both
max, we’re actually just calling the original function
f. The original function
f simply returns 1 + the value of the input which in this case was four.
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