函数不会存储值

Question

I am trying to write a Python script with a function.

The code below works as expected, it prints 3.

def function(a,b):
  k = a+b
  print(k)

a = 1
b = 2
function(a,b)

But when I move the print statement outside the function like this, it won't work.

def function(a,b):
  k = a+b

a = 1
b = 2
function(a,b)

print(k)  # -> NameError: name 'k' is not defined

Any ideas on how to not have the print statement inside the function and still get this code to work?

Answer 1

k is a local variable defined inside the function.

Case 1: Just return it:

def function(a,b):
    k = a+b
    return k # just return, does not make it global

a = 1
b = 2
k = function(a,b)
# 3
print(k) # variable was returned by the function

---

Case 2: Make it global:

def function(a,b):
    global k #makes it global
    k = a+b

function(a,b)
print(k) # it is global so you can access it

Please read more here

Answer 2

Instead of setting a global variable (global variables are often bad), why not return the result and print it?

Something like

def function(a,b)
  return a+b

print(function(1,2))