# Class 12: Scope of variables | global Keyword

Introduction to global Keyword

In Python, global keyword allows you to modify the variable outside of the current scope. It is used to create a global variable and make changes to the variable in a local context.

Rules of global Keyword

The basic rules for global keyword in Python are:

• When we create a variable inside a function, it’s local by default.

• When we define a variable outside of a function, it’s global by default. You don’t have to use global keyword.

• We use global keyword to read and write a global variable inside a function.

• Use of global keyword outside a function has no effect

Example 1:
Accessing global Variable From Inside a Function

```c=100 	#global variable
def sample():
print(c)

#function calling
sample()
print(c)
```

Output:

100
100
>>>

However, if we try to modify the global variable from inside a function, we get an error as shown in the below program.

Example 2:

Modifying Global Variable From Inside the Function

```c=100 	#global variable
def sample():
c=c+10
print(c)

#function calling
sample()
print(c)```

Output:

When we run above program, the output shows an error:

UnboundLocalError: local variable ‘c’ referenced before assignment

Note: This is because we can only access the global variable but cannot modify it from inside the function.

The solution for this is to use the global keyword.

Example 3:

Changing Global Variable From Inside a Function using global

```c = 100 # global variable
def abc():
global c
c = c + 200 # increment by 200
print("Inside abc():", c)

#function calling
print("Outside Function abc() :", c)
print("Outside Function abc() :", c)
```

Output:

Outside Function abc() : 100
Outside Function abc() : 300
>>>

In the above program we have

global c

It states that c is a global variable and its value can be modified inside the function abc().

so when we increment the variable c by 200, i.e c = c + 200. we get the modified value as output.

As we can see, change also occurred on the global variable outside the function, c = 300.

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