您可以为返回的对象分配值吗？

Question

I am trying to implement Euclid's algorithm in Python3. If max(a, b) returns the object with the largest value in (a, b), why can't you operate on that object like so:

max(a, b) %= min(a, b)

Answer 1

>>> a = 5
>>> b = 6
>>> max(a, b) %= min(a, b)
  File "<stdin>", line 1
SyntaxError: can't assign to function call

The interpreter has spoken. You are trying to operate on a value/object, which is not possible. Assignments can be performed on variables only, which are references pointing to said values/objects.

Even if you could do it, it's pointless, because you're trying to change the return value of a function, that hasn't been captured by any variable. You can't even use it.

Answer 2

I believe the short answer to your question is no . The function max(a,b) is returning the largest value to you, not a variable reference to the largest value.

I believe what you are looking for is:

if max(a,b) == a:
    a %= min(a,b)
else
    b %= min(a,b)

which will check if the largest value is indeed the variable a before the assignment.

Answer 3

You can only assign to variables, but there's no way for a function to return a variable. (It can only return a value.)

For example:

a = 4
b = 5
max(a, b)  # What does this return?

max(a, b) returns the value 5 , not the variable b . (So the code you're trying to write is essentially 5 = ... which makes little sense.)

Answer 4

You can't do like this, the function max returns a value, not a variable, what you can do, however is to execute:

a,b = sorted((a,b))

then, after this line, a will always be the greater value (or equal b )

this way you can just do in the line after:

a%=b

Since b will be the min value...