python pass by value and pass by pointer;change value of variable when calling function;

Question

i want to change value of a variable like below c++ code in python
is it any way ?
void fun(int *anyint)
{ *anyint = 200; }

int main(){
int var=100;
cout<<"var before fun call "<<var<<endl; //o/p=>var=100
fun(&var);
cout<<"var after fun call "<<var<<endl; //o/p=>var=200
}
-----------------------------------
in python i didnt find any way to perform like above c++ code

var = 100
def fun(anyvar):
anyvar = 200
print("anyvar value inside fun ",anyvar)

print("var value before fun call ",var)
fun(var)
print("var value after fun call ",var)

i want to change the value of variable 'var' when calling the function 'fun()';
variable name 'var' is not fixed it may vary .is it any way?

i'm new to Python ;
Thanks in advance

Answer 1

This is one way.
https://code.sololearn.com/cAuMANyKC91R/?ref=app

Answer 2

you cannot pass variable by reference if they hold basic types... however that's what's done for objects (and you must explicitly clone object to mimic passing by value)

so:

def fun(anyvar):
anyvar = 200

val = 100
print(val) # 100
fun(val)
print(val) # 100

but:

def objfun(anyvar):
anyvar['prop'] = 200

obj = {'prop':100}
print(obj) # {'prop':100}
objfun(obj)
print(obj) # {'prop':200}

anyway assigning the fun/objfun local variable won't work in both... but you could workaround by wrapping target variable inside a dict (used as namespace), and have this kind of function:

def dictfun(anydict,prop):
anydict[prop] = 200

and call it as:

dct = { val: 100 }
dictfun(dct,'val')

Answer 3

Avinesh thanks for your answer;but one problem sometimes we dont know the variable name passing;so the variable name var maybe anothor;that situation global keyword has no use;

Answer 4

visph thanks for the reply.