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Within Python, as a programming language, there are different types of variables. At this article, we’ll see a brief explanation about them and show you how to use a global variable inside a function.
 

Definition of global variable in Python

A global variable in Python is one that is not defined within the scope of the function that is using it. For example:

variable_global = 0
x = 42
v = 1

Definition of local variable in Python

When you set the value of the variable within the function, it is a local variable. An example of a local variable is shown below:

def f():    
 v = 10 
print v

This local variable can only be used after it has been defined within the function. If you try to use it before it is inserted into the code, an error message will happen:

def f():
  print  v
 v = 10
UnboundLocalError: Local variable 'v' referenced before assignment.

Using a global variable in a function:

To use a global variable within a function, you must declare it as global within that function.

v = 1
 def f():    
  global v     
print  v

This code above allows you to use the global value within the function, without actually having to declare its value within the function. One difference between the global and local variables in Python is that the global variable can be declared after the function that will use it, without happening an error like the mentioned before. This can be seen in the example:

def f ():     
 print  x  
x = 42
42

You may declare a value for the global variable in the function. This causes the value of this variable takes the value written within the function, from this point on in the code.

x = 3
 def f (): 
  global  x     
   x = 1 
print  x 
'1'

Attention: Be careful when doing this, because the control of these value changes can be very complex.

If you know more ways how to use a global variable within a function, share it in the comments area below.

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