Python Variables
Table Of Contents
- What Is A Variable?
- Variable Naming Rules.
- Variable Declaration.
- Assigning A Single Value To Multiple Variables.
- Assigning Different Values To Multiple Variables.
- Getting The Data Type Of A Variable.
- Global And Local Variables In Python.
- Delete A Variable.
(1) What Is A Variable?
- Variable is a place in the memory location, where we store our values and give it a name.
- Computer is having two types of memory location (Temporary Memory- RAM and Permanent Memory – ROM), variables store in the Temporary memory (RAM).
- In Python, We do not need to declare variables before using them or declare their type. A variable is created the moment we first assign a value to it.
- A variable is a name given to a memory location. It is the basic unit of storage in a program.
(2) Variable Naming Rules.
- The variable is a combination of character digits and underscore and the character includes letters in lowercase (a-z), letters in uppercase (A-Z), digits (0-9), and an underscore (_).
- A variable cannot begin with a digit. If an identifier starts with a digit, it will give a Syntax error.
- In Python, keywords are the reserved names that are built-in to Python, so a keyword cannot be used as an identifier – they have a special meaning and we cannot use them as identifier names.
- Special symbols like! @, #, $, %, etc. are not allowed in variable names.
- Python variable names cannot only contain digits.
- There is no restriction on the length of the variable.
- Variable names are case-sensitive.
(3) Variable Declaration.
- Python is not “statically typed”. We do not need to declare variables before using them or declare their type.
- A variable is created the moment we first assign a value to it.
- A Python variable is a name given to a memory location. It is the basic unit of storage in a program.
Example-1
# Variable-1
mark = 98.89
# Variable-2
division = "First"
# Variable-3
course = "Science"
# Variable-4
subjects = ['Math','Science','History','Geography','Biology']
print("Mark:", mark, " \nDivision : ",division , "\nCourse: ",course, "\nSubjects: ", subjects)Output:
Mark: 98.89
Division: First
Course: Science
Subjects: [‘Math’, ‘Science’, ‘History’, ‘Geography’, ‘Biology’](4) Assigning A Single Value To Multiple Variables.
- You can assign a single value to multiple variables at a time using the assignment (=) operator.
Example-1
a = 10
b = 10
c = 10
d = 10
print(a,b,c,d)a = b = c = d = 10
print(a,b,c,d)Output:
10, 10, 10, 10(5) Assigning Different Values To Multiple Variables.
- You can assign different values to multiple variables at a time using the coma ( , ) operator.
Example-1
a = 98.45
b = "First"
c = "Science"
d = ['Physics','Chemistry','Math']
print(a,b,c,d)a , b , c , d , = 98.45,"First","Science",['Physics','Chemistry','Math']
print(a,b,c,d)Output:
98.45, “First”, “Science”, [‘Physics’,’Chemistry’,’Math’](6) Getting The Data Type Of The Variables.
- We can get the data type of a variable with the type() built-in function.
- It will return you the Data Type of the variable.
Example-1
a = 98.45
b = "First"
c = "Science"
d = ['Physics','Chemistry','Math']
print(type(a))
print(type(b))
print(type(c))
print(type(d))Output:
<class ‘float’>
<class ‘str’>
<class ‘str’>
<class ‘list’>(7) Global & Local Variables In Python
(a) Local Variable
- Variables that are defined inside a function body have a local scope. These variables are called local variables.
- This means that local variables can be accessed only inside the function in which they are declared.
Example-1
def localVariable():
x = 10
y = "Hello World!"
print(x,y)
localVariable()Output:
10 Hello World!Note:
Here ‘x’ and ‘y’ are declared inside of the function body, Hence these are called ‘Local Variables’.
Example-2
def localVariable():
x = 10
y = "Hello World!"
print(x)
print(y)Output:
NameError: name ‘x’ is not definedNote:
You can not access local variables outside of its scope. It will give you a “Name Error”.
(b) Global Variable
- Variables that are defined outside of the function body have a global scope.
- This means the Global Variables can be accessed outside of the function .
Example-1
x = 10
y = "Hello World!"
def localVariable():
print(x,y)
localVariable()Output:
10 Hello World!Note:
Here ‘x’ and ‘y’ are declared outside of the function body, Hence these are called ‘Global Variables’.
(8) Deleting A Variable.
- We can also delete a variable using the (del) command.
- It will permanently delete the variable from the memory.
Example-1
x = 10
del(x)
print(x)Output:
NameError: name ‘x’ is not defined