数学运算顺序

Question

new to programming and came across this while doing a worksheet:

x = 1 / 2 + 3 // 3 + 4 ** 2

what is x ?

I read that in regards to the exponent you have to read it right to left, and I did that and I keep getting 0 for some reason even though the answer was supposed to be 17.5. Any help on why/how I am supposed to get 17.5 and the order I was supposed to work it out from would be greatly appreciated. thanks.

Answer 1

Using Python, the result is 17.5

You can check the order of the mathematical operators in python (Python Operator Precedence) for more information

(1 / 2) + (3 // 3) + (4 ** 2) = 0.5 + 1 + 16

Ref: https://www.mathcs.emory.edu/~valerie/courses/fall10/155/resources/op_precedence.html

Answer 2

To determine the order of precedence for this expression, keep in mind these rules (non-exhaustive):

• evaluation goes from left to right
• Multiplication/division has higher precedence than addition/subtraction (eg 1 + 2 / 3 gets evaluated as 1 + (2 / 3) )
• Exponent/power has higher precedence than multiplication and division (eg 1 / 2**4 gets evaluated as 1 / (2**4) )

These rules together show us that this expression:

x = 1 / 2 + 3 // 3 + 4 ** 2

Will be evaluated as:

x = (1 / 2) + (3 // 3) + (4 ** 2)

Therefore, x = 0.5 + 1 + 16 = 17.5.

Answer 3

The operator precedence is defined in the Python documentation:

https://docs.python.org/3/reference/expressions.html#operator-precedence

So, ** has the highest precedence, then / and // and then + .