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Getting started in python variables

  


                                 

                                   Getting started in python variables

    Hi friends welcome back to another tutorial in python programming language, in our previous tutorial in python we learnt the origin of python and  how to install python on a windows computer. now in this tutorial we will be going further in learning about variables in python.

Here’s what you’ll learn in this tutorial: You will learn how every item of data in a Python program can be described by the abstract term object, and you’ll learn how to manipulate objects using symbolic names called variables.

TABLE OF CONTENTS

Introduction


    A variable is a general and fundamental concept in every programming language. It is a reserved memory location that stores and manipulates a given set of data. This tutorial on Python variables will help you learn more about what they are, the different data types of variables, and the rules for naming variables in Python.

Variables are entities of a program that holds a value. Here is an example of a variable:

variable1 = 'pyduino.blogspot.com'
variable2 = 3044

 If you’re writing a complex code, your program will need data that can change as program execution proceeds.Think of a variable as a name attached to a particular object. In Python, you don't need to  declared or defined a variable in advance, as is the case in many other programming languages. To create a variable, you just assign it a value and then start using it. Assignment is done with a single equals sign (=). Python allows the use of chained assignment, which makes it possible to assign the same value to several variables simultaneously, e.g;

>>> c = f = z = 590
the chained assignment above assigns 
590
to the variables c, f
, and z simultaneously.
                    

Types of variables in python programming language

  

In many programming languages, variables are statically typed. That means a variable is initially declared to have a specific data type, and any value assigned to it during its lifetime must always have that type.

Variables in Python are not subject to this restriction. In Python, a variable may be assigned a value of one type and then later re-assigned a value of a different type:

 

>>> var = 2366
>>> print(var)
2366

>>> var = "pyduino.blogspot.com"
>>> print(var)
pyduino.blogspot.com
We can even store a variable to our variable, or an operation with our 
variables to a variable. Something like var3 = (var2/var1) would work. 
You can store other things, like functions, as well to variables.
 In all of the examples above, we only assigned a single value to the 
variables. Python has specific data types or objects that hold a 
collection of values, too. A Python List is one such example.
 var = [15,16,17]
 

You can extract the values from the list using the index position method. In lists, the first element index position starts at zero, the second element at one, the third element at two, and so on.

To extract the first element from the list x:

print(x[0])

 >>> 15

 

To extract the second element from the list x:

print(x[1])

>>> 16

 

To extract the third element from the list x:

print(x[2])

>>> 17

 

Suppose you want to assign values to multiple variables. Instead of having multiple lines of code for each variable, you can assign it in a single line of code just like below.

(x, y, z)=5, 10, 5

print(x,y,z)

>> 5 10 5.

 

                                        

Rules in naming variables


1. A variable name must begin with a letter of the alphabet or an underscore(_)

Example: abc=100 #valid syntax

    _abc=100 #valid syntax

    3a=10 #invalid syntax

    @abc=10 #invalid syntax

2. The first character can be followed by letters, numbers or underscores.

Example: a100=100 #valid

    _a984_=100 #valid

    a9967$=100 #invalid

    xyz-2=100 #invalid

3. Python variable names are case sensitive.

Example: a100 is different from A100.

    a100=100

  A100=200


4. Reserved words cannot be used as variable names.

Example: break, class, try, continue, while, if

break=10

class=5

try=100


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