Variable In Python
§ Variable is a name which is used to store the value in
a memory location. Variable
also known as identifier and used to hold value.
also known as identifier and used to hold value.
§ Since python is a type infer language, we don't need
to specify the type of
variable.it is smart enough to get variable type.
variable.it is smart enough to get variable type.
Assigning value to variable
§ With the help of python, we don‘t need to declare the
variable first and then to use it. Python allows us to create variable at
required time.
§ Whenever we assign any value to the variable that
variable is declared automatically.
§ We used equal (=) operator to assign value to a
variable.
To create a variable in Python, all you need to do is specify the variable name, and then assign a value to it.
Eg: These are different
ways to assign value to a variable
Single Assignment
a=10
b=20.3
c=’hello’
print(a)
print(b)
print(c)
Multiple Assignment
§ We can assign a value to multiple variable in a single
line or statement.
We can use multiple assignments in two ways: 1. either by assigning a single value to multiple variables in a single line/statement or
2. assigning multiple values to multiple variables.
Assigning single value to multiple variables
a=10
b=10c=10
print(a)
print(b)
print(c)
a=b=c=10
print(a)print(b)
print(c)
2.Assigning multiple values to multiple variables:
a,b,c=10,20,30
print(a)
print(b)print(c)
Note:-
§ The values will be assigned in the order in which
variables appears.
Rules to define identifiers in Python:-
1.
In the name of identifier the only allowed character is -
§ Alphabet symbols (both upper case and lower case)
§ digits (0 to 9)
§ underscore (_)
By mistake if we are using other symbol python immediate gives error.
2. Every Identifier name should not start with digit.
4.
No keywords should access as a identifier keywords
are not allowed as a identifier.
5. No length limit.
§ In python Identifiers can be variable name, class
name or method name.
Rules to define identifiers in Python:-
§ Alphabet symbols (both upper case and lower case)
§ digits (0 to 9)
§ underscore (_)
By mistake if we are using other symbol python immediate gives error.
amount=10 //valid
amoun$t =10 //invalid2. Every Identifier name should not start with digit.
abc123
=10 //valid
123abc = 10
//invalid
3. Identifiers are case sensitive
total=10
TOTAL=20
5. No length limit.
Note:-
1 23hello //invalid
hello123 //invalid
java
Note:-
123hello //invalid
hello123 //invalid
java
Note-
_x ==> private
§ If identifier start with underscore (_) symbol it indicates private
identifier.
__x ==> strongly private
§ If identifier start with two underscore (__) symbol it is strongly
associated.
__x __ ==> language
defined special name
§ If the identifier starts and ends with two underscore symbols then the
identifier is language defined special name, which is also known as magic
methods.
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