change global variable value dynamically inside a function

Question

To change a global variable inside a function we could proceed as follow:

let's say the global variable has 'x' as a name:

def change_x_globally( new_value ):
    global x 
    x = new_value

such an approach requires to hardcode the name of the variable beforehand, in case of multiple global variables this approach becomes cumbersome and unpractical

so I would input the name of the global variable e.g: if we wanted to change x we would input the string "x"

hence the desired final function would have the following signature:

def change_global_variable( variable_name, new_value ):
    pass

any ideas?

@MegaIng can u provide how can we implement it using a class, curious to see your approach, thanks in advance — rachid el kedmiri, Apr 24 '18 at 14:19
I don't like the proposed duplicate. Looks like contrived convoluted mess combined with "lack of basic understanding". What did the linked question even try to do? Save variables (instead of their values) in a list? I don't know.... I find this question shorter and clearer. — Andrey Tyukin, Apr 24 '18 at 19:04

score 3 · Answer 1 · answered Apr 24 '18 at 14:14

3

You can use globals() to get back a dictionary of your globals, which you then address by string, e.g., globals()['x'] = new_value

answered Apr 24 '18 at 14:14

Wolf

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score 1 · Answer 2 · answered Apr 24 '18 at 14:27

You should not change global values from within a function. If you want to do that, use either a global dict as proposed by @chepner or use a class.

dict idea:

values = {"x":0,"y":1}
def test(5):
    values["x"]=5

class idea:

class Values:
    x = 0
    y = 0
    # possibility one: class gets instantiated and then the main method gets called
    def run(self): 
        self.x = 4

# possibility two: class doesn't get instantiated and the values are written two by module level functions
def test(v):
    Values.x = v

change global variable value dynamically inside a function

2 Answers2