Make a variable update its value based on returns

Question

I'm having an issue because i have to run the same function many times and want to record a total for every time it was run.

def add(word):
    total_hello=0
    total_world=0
    if word=="hello":
       total_hello+=1
    elif word=="world":
       total_world+=1

    print(total_hello)
    print(total_world)
    return total_hello, total_world

hello=0
world=0
hello, world+=add("hello")
hello, world+=add("world")
hello, world+=add("hello")
print(hello)
print(world)

Making hello a variable and trying to make it += the return doesn't work. Is there anything simple i can do to add the returns efficiently?

`hello, world` makes a tuple. You can't use `+=` like that to add from a tuple to a tuple. — Mark, Apr 20 '20 at 04:54
if you redefine the `+=` then you can, but not in the vanilla form — Bryce Wayne, Apr 20 '20 at 04:55
Please add the traceback so we see the exact error. Also, what would you like to happen? Do you want to add the 2 output values to `hello` and `world`? — tdelaney, Apr 20 '20 at 04:56
Use global variables or pass the variable reference to the function and update them. — thuva4, Apr 20 '20 at 04:59

abhiarora · Accepted Answer · 2020-04-20T05:09:32.457

Making hello a variable and trying to make it += the return doesn't work. Is there anything simple i can do to add the returns efficiently?

You can't just add the elements of tuple returned by your function to the tuple's element on left-hand side. You have following options:

The variables (total_hello and total_world) are local to your function and they are reassigned every-time you call your function to 0. Try moving them outside your function and make them global. They can be used to store the count of the variables.

# Code in Module 1:
total_hello=0
total_world=0

def add(word):
    global total_hello, total_world
    if word=="hello":
       total_hello+=1
    elif word=="world":
       total_world+=1

    return total_hello, total_world


# Code in Module 2:
# from Module1 import *
add("hello")
add("world")
hello, world = add("hello")
print(hello)
print(world)

See this answer for a more Pythonic way.
Using default arguments in Python:

def add(word, total_world=[0], total_hello=[0]):
    if word == "hello":
       total_hello[0] += 1
    elif word == "world":
       total_world[0] += 1

    return total_hello[0], total_world[0]


add("hello")
add("world")
hello, world = add("hello")
print(hello)
print(world)

I ran this code and it works for me. Point it out where it is failing for you1 — abhiarora, Apr 20 '20 at 04:58
Wasn't working on my code in the beginning but I figured it out thank you so much global helps — FATCAT47, Apr 21 '20 at 05:02

score 1 · Answer 2 · answered Apr 20 '20 at 05:24

You can directly use hello and world inside function.

hello=0
world=0
def add(word):
    global hello, world
    if word=="hello":
       hello+=1
    elif word=="world":
       world+=1

    print(hello)
    print(world)

add("hello")
add("world")
add("hello")

print(hello)
print(world)

Make a variable update its value based on returns

2 Answers2