Use the result of the return of one function in another function

Question

I know there are several questions about this, I read but I could not understand. I'm trying to use the result of the return of one function in another:

def multiplication(a):
    c = a*a
    return c

def subtraction(c):
    d = c - 2
    return d

print(subtraction(c))

Output:

NameError: name 'c' is not defined

I know that there is a possibility of using global variables, but I have seen that this is not a good idea since the variables can change their value.

EDIT:

These two functions are just idiotic examples. I have two functions with words and I need to use the return of the first function in the second function. In case of this my idiotic example, I need the result of the first function (c) in the second function.

What are you specifically trying to do? You want to multiply something and subtract something? What actual calculation are you trying to do? — khelwood, Jul 19 '18 at 12:42
Change to c to a value? Even global variable, you have to have a value or ANYTHING for python to RUN.... — Marcus.Aurelianus, Jul 19 '18 at 12:42
`c` is just a local variable, it doesn't exit outside the `multiplication` function. To use the result of the function, you have to call the function. — Fernando Cezar, Jul 19 '18 at 12:43
For cases where multiple values are returned as a tuple, see also https://stackoverflow.com/questions/19256989. — Karl Knechtel, Jun 05 '22 at 16:29
In order for there to be a "result of the first function" to use in the second function, it at least has to be called somewhere first. — Karl Knechtel, Jul 04 '22 at 21:25

score 3 · Accepted Answer · answered Jul 19 '18 at 12:42

You are not calling your functions properly.

def multiplication(a):
    c = a*a
    return c

def subtraction(c):
    d = c - 2
    return d

# first store some value in a variable
a = 2

# then pass this variable to your multiplication function
# and store the return value
c = multiplication(a)

# then pass the returned value to your second function and print it
print(subtraction(c))

WhiteHotLoveTiger · Answer 2 · 2018-07-19T12:54:42.283

Does this makes things clearer?

def multiplication(a):
    c = a*a
    return c

def subtraction(c):
    d = c - 2
    return d

print(multiplication(5))               # 25
print(subtraction(5))                  #  3
print(multiplication(subtraction(5)))  #  9
print(subtraction(multiplication(5)))  # 23

I think you're trying to do what's happing in the last print statement: first call the multiplication function, and then call the subtraction function on the result.

Note that the variable c in your multiplication function is an entirely different variable from the c in your subtraction function. So much so, that it may make things more clear to rename your variables, perhaps something like this:

def multiplication(a):
    product = a * a
    return product

def subtraction(a):
    difference = a - 2
    return difference

score 1 · Answer 3 · answered Jul 19 '18 at 12:42

1

So why not use return value?

print(subtraction(multiplication(24)))

?

answered Jul 19 '18 at 12:42

bipll

11,747
1
18
32

This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - [From Review](/review/low-quality-posts/20347703) – Ivan Jul 19 '18 at 14:39
Oh really? Sp, my reply does not say anything about how "to use the result of the return of one function in another", does it? – bipll Jul 20 '18 at 05:35

score 1 · Answer 4 · answered Jul 19 '18 at 12:46

1

'c' is not declared outside the 'subtraction' function. You need to give need to declare 'c' before printing. Let's say you want 'c' to be 5, then:

c = 5
print(subtraction(c))

answered Jul 19 '18 at 12:46

guygrinberger

327
2
14

doctorlove · Answer 5 · 2018-07-19T13:00:45.870

You have defined two functions which both return a number.

If you call subtraction(c) you will get the error you see, because there is no c.

If you define a c in scope of the print statmenet

c = 42
print(subtraction(c))

it will be ok.

Try thinking of it like this: each function takes a variable does things to it and returns a number.

e.g.

>>> multiplication(101)
10201

That this happened to be called c isnide the function isn't known outside the function (i.e scope).

You can save the number to a variable

>>> x = multiplication(101)

Then x remembers that value. Or

>>> c = multiplication(101)

This is not the same c as you have inside the functions.

(And after the question edit):

Decide what value you want to call the first function with, for example 101:

>>> c = multiplication(101)

then use that return to call the next function:

>>>> subtraction(c)

Or just chain them togther:

subtraction( multiplication(101) )

To start the chain you will need to use a string, int or defined variable. Otherwise you get name not defined errors. Once a variable is used in a function it goes out of scope when the function ends.

Use the result of the return of one function in another function

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