CODEWITHSUNDEEP
pythonpython-3.xfunction
notacorn
notacorn

Reputation: 4099

What's the best way to modify a variable using a function, but inside of another function?

The main problem I'm running into (specific to Python, don't mark as duplicate for another language please) is that I don't know how to modify a string variable inside a function, with a nested function, if that makes any sense. This code should do a much better job explaining what I mean.

def insideAFunction():
    variableToMod =  "test"

    def modFunc():
        if 1 > 0:
            variableToMod = "TEST"

    print("before: " + variableToMod)
    modFunc()
    print("after: " + variableToMod)


def insideAFunction2():
    variableToMod =  "test"

    def modFunc():
        global variableToMod
        if 1 > 0:
            variableToMod = "TEST"

    print("before: " + variableToMod)
    modFunc()
    print("after: " + variableToMod)

insideAFunction()
insideAFunction2()

Output:

before: test
after: test
before: test
after: test

The desired output would be:

after: TEST

I know I can get it to work by just defining variableToMod outside the insideAFunction() and make the global call like in insideAFunction2(), but I want to know if it's possible to do it completely inside the function.

Upvotes: 1

Views: 55

Answers (3)

Wisang Jati Anggoro
Wisang Jati Anggoro

Reputation: 153

Use return function works fine on me:

def insideAFunction():
    variableToMod =  "test"

    def modFunc():
        if 1>0:
            variableToMod = "TEST"
            return variableToMod

    print("before: " + variableToMod)
    variableToMod = modFunc()
    print("after: " + variableToMod)

insideAFunction()

the output is:

before: test
after: TEST

Upvotes: 0

nish
nish

Reputation: 1044

  1. You are changing value of variableToMod in modFunc but not returning it.
  2. Second print variableToMod statement is still printing but it takes the variableToMod you declared in line 2

So it will always print the same. You need to return a value from modFunc and assign it to outer variableToMod before printing. This way the result will be

before: test after: TEST

def insideAFunction2(): variableToMod = "test"

def modFunc():
    if 1 > 0:
        variableToMod = "TEST"
        return variableToMod


print("before: " + variableToMod)
variableToMod = modFunc()
print("after: " + variableToMod)

Upvotes: 1

Broseph
Broseph

Reputation: 1763

You are probably using Python 3.x (I don't believe this is an issue in Python 2.x), which means you need to use the nonlocal keyword in your inner functions.

I'm guessing the version using global doesn't work because you've already defined a local variable with the same name, which would shadow any global variable with that name.

EDIT: Actually, Python 2.x does have this same behavior, but it doesn't support the nonlocal statement it seems. I guess one solution might be to pass in the local() dictionary and change the entries in that inside your inner function, but I'm not sure that would work. I'd have to try it out.

Upvotes: 0

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