What is difference between global and local variable tell me any 3 to 4 differences?

Question

In C programming language, variables defined within some function are known as Local Variables and variables which are defined outside of function block and are accessible to entire program are known as Global Variables.

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Local Vs. Global Variable
Global Variables
Global Keyword:

This article explains the difference between local and global variables.

Local Vs. Global Variable

Those variables which are defined within some function and are accessible to that function only are called Local Variables.

Those variables which are defined outside of function block and are accessible to entire program are known as Global Variables.

Scope is local to that block or function where they are defined.

Scope is global i.e. they can be used anywhere in the program.

Default value is unpredictable (garbage).

Default value is Zero (0).

Example:


#include
void main()
{
   int x=23, y=4;
   printf(“x = %d and y=%d”,x,y);
}

Here x and y are local variables.

Example:


#include
int a=10,b;
void main()
{
  printf(“a = %d and b=%d”,a,b);
}

Here a and b are global variables.

Global variables are those which are not defined inside any function and have a global scope whereas local variables are those which are defined inside a function and its scope is limited to that function only. In other words, we can say that local variables are accessible only inside the function in which it was initialized whereas the global variables are accessible throughout the program and inside every function. Local variables are those which are initialized inside a function and belong only to that particular function. It cannot be accessed anywhere outside the function. Let’s see how to create a local variable.

Example: Creating local variables

Python3

def f():

s = "I love Geeksforgeeks"

print(s)

f()

Output

I love Geeksforgeeks

If we will try to use this local variable outside the function then let’s see what will happen.

Example:

Python3

def f():

s = "I love Geeksforgeeks"

print("Inside Function:", s)

f()

print(s)

Output:

NameError: name 's' is not defined

Global Variables

These are those which are defined outside any function and which are accessible throughout the program, i.e., inside and outside of every function. Let’s see how to create a global variable.

Example: Defining and accessing global variables

Python3

def f():

print("Inside Function", s)

s = "I love Geeksforgeeks"

f()

print("Outside Function", s)

Output

Inside Function I love Geeksforgeeks
Outside Function I love Geeksforgeeks

The variable s is defined as the global variable and is used both inside the function as well as outside the function.

Note: As there are no locals, the value from the globals will be used but make sure both the local and the global variables should have same name.

Now, what if there is a variable with the same name initialized inside a function as well as globally. Now the question arises, will the local variable will have some effect on the global variable or vice versa, and what will happen if we change the value of a variable inside of the function f()? Will it affect the globals as well? We test it in the following piece of code:

Python3

def f():

s = "Me too."

print(s)

s = "I love Geeksforgeeks"

f()

print(s)

Output

Me too.
I love Geeksforgeeks

If a variable with the same name is defined inside the scope of function as well then it will print the value given inside the function only and not the global value.

The question is, what if we try to change the value of a global variable inside the function. Let’s see it using the below example.

Example:

Python3

def f():

s += 'GFG'

print("Inside Function", s)

s = "I love Geeksforgeeks"

f()

Output:

UnboundLocalError: local variable 's' referenced before assignment

To make the above program work, we need to use the “global” keyword. Let’s see what this global keyword is.

Global Keyword:

We only need to use the global keyword in a function if we want to do assignments or change the global variable. global is not needed for printing and accessing. Python “assumes” that we want a local variable due to the assignment to s inside of f(), so the first statement throws the error message. Any variable which is changed or created inside of a function is local if it hasn’t been declared as a global variable. To tell Python, that we want to use the global variable, we have to use the keyword “global”, as can be seen in the following example:

Example 1: Using global keyword

Python3

def f():

global s

s += ' GFG'

print(s)

s = "Look for Geeksforgeeks Python Section"

print(s)

s = "Python is great!"

f()

print(s)

Output

Python is great! GFG
Look for Geeksforgeeks Python Section
Look for Geeksforgeeks Python Section

Now there is no ambiguity.

Example 2: Using global and local variables

Python3

a = 1

def f():

print('Inside f() : ', a)

def g():

a = 2

print('Inside g() : ', a)

def h():

global a

a = 3

print('Inside h() : ', a)

print('global : ', a)

f()

print('global : ', a)

g()

print('global : ', a)

h()

print('global : ', a)

Output

global :  1
Inside f() :  1
global :  1
Inside g() :  2
global :  1
Inside h() :  3
global :  3

This article is contributed by Shwetanshu Rohatgi. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to . See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or if you want to share more information about the topic discussed above.

Global variable Java Local variable

What is difference between global and local variable tell me any 3 to 4 differences?

Local Vs. Global Variable

Python3

Python3

Global Variables

Python3

Python3

Python3

Global Keyword:

Python3

Python3

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