Advance Programming Practice for Everybody using Python

Structured Programming Paradigm

Procedural Programming Paradigm

Object-Oriented Programming

Declarative paradigm

Structured Programming Paradigm

•Structured programming is a paradigm that is based on improving clarity and quality of programs by using subroutines, block structures and loops (for and while) and discouraging the use of goto statement.

Structured code for the individual modules:

Structured coding relates to division of modules into set of instructions organized within control structures. A control structure defines the order in which a set of instructions are executed. The statements within a specific control structure are executed:

•sequentially – denotes in which order the controls are executed. They are executed one after the other in the exact order they are listed in the code.

•conditionally – allows choosing which set of controls is executed. Based on the needed condition, one set of commands is chosen while others aren’t executed.

•repetitively – allows the same controls to be performed over and over again. Repetition stops when it meets certain terms or performs a defined number of iterations.

SIMPLE IF

if test expression:

statement(s)

IF….ELSE

if test expression:

Body of if

else:

Body of else

IF...ELIF...ELSE

if test expression:

Body of if

elif test expression:

Body of elif

else:

Body of else

NESTED IF

if test expression:

if test expression:

Body of if

else:

Body of else

else:

Body of else

Procedural Programming Paradigm

•In a multi-function program, many important data items are placed as global so that they may be accessed by all functions. Each function may have its own local data. If a function made any changes to global data, these changes will reflect in other functions. Global data are more unsafe to an accidental change by a function. In a large program it is very difficult to identify what data is used by which function.

•A function is a block of organized, reusable code that is used to perform a single, related action. Functions provide better modularity for your application and a high degree of code reusing.

•There are 2 types of function

Built-in function ex. Print() max(3,4) min(3,4), len(), range(), Round(),int(), float(), input(), tuple()

User defined function -User can create their own functions.

•Function blocks begin with the keyword def followed by the function name and parentheses ( ( ) ).

•Any input parameters or arguments should be placed within these parentheses. You can also define parameters inside these parentheses.

•The first statement of a function can be an optional statement - the documentation string of the function or docstring.

•The code block within every function starts with a colon (:) and is indented.

•The statement return [expression] exits a function, optionally passing back an expression to the caller. A return statement with no arguments is the same as return None.

Object-Oriented Programming

It is an approach that provides a way of modularizing programs by creating partitioned memory area for both data and functions that can be used as templates for creating copies of such modules on demand. Thus the object is considered to be a partitioned area of computer memory that stores data and set of operations that can access that data.

•Objects

•Classes

•Data Abstraction and Encapsulation

•Inheritance

•Polymorphism

•Dynamic Binding

•Message Passing

Declarative paradigm

•Declarative programming is a programming paradigm that expresses the logic of a computation without describing its control flow.

•Logic, functional and domain-specific languages belong under declarative paradigms

Examples would be HTML, XML, CSS, SQL, Prolog, Haskell, F# and Lisp.

•Declarative code focuses on building logic of software without actually describing its flow. You are saying what without adding how. For example with HTML you use <img src="./image.jpg" /> to tell browser to display an image and you don’t care how it does that.

Control Structures in Python

Most programs don't operate by carrying out a straightforward sequence of statements. A code is written to allow making choices and several pathways through the program to be followed depending on shifts in variable values.

All programming languages contain a pre-included set of control structures that enable these control flows to execute, which makes it conceivable.

This tutorial will examine how to add loops and branches, i.e., conditions to our Python programs.
Sequential - The default working of a program

Selection - This structure is used for making decisions by checking conditions and branching

Repetition - This structure is used for looping, i.e., repeatedly executing a certain piece of a code block.

Sequential

Sequential statements are a set of statements whose execution process happens in a sequence. The problem with sequential statements is that if the logic has broken in any one of the lines, then the complete source code execution will break.

Code

# Python program to show how a sequential control structure works

# We will initialize some variables

# Then operations will be done

# And, at last, results will be printed

# Execution flow will be the same as the code is written, and there is no hidden flow

a = 20

b = 10

c = a - b

d = a + b

e = a * b

print("The result of the subtraction is: ", c)

print("The result of the addition is: ", d)

print("The result of the multiplication is: ", e)

Output:

The result of the subtraction is:  10

The result of the addition is :

30

The result of the multiplication is:  200

Selection/Decision Control Statements

The statements used in selection control structures are also referred to as branching statements or, as their fundamental role is to make decisions, decision control statements.

A program can test many conditions using these selection statements, and depending on whether the given condition is true or not, it can execute different code blocks.

There can be many forms of decision control structures. Here are some most commonly used control structures:

• Only if

• if-else

• The nested if

• The complete if-elif-else

Simple if

If statements in Python are called control flow statements. The selection statements assist us in running a certain piece of code, but only in certain circumstances. There is only one condition to test in a basic if statement.

The if statement's fundamental structure is as follows:

Syntax

if <conditional expression> :

The code block to be executed if the condition is True

These statements will always be executed. They are part of the main code.

All the statements written indented after the if statement will run if the condition giver after the if the keyword is True. Only the code statement that will always be executed regardless of the if the condition is the statement written aligned to the main code. Python uses these types of indentations to identify a code block of a particular control flow statement. The specified control structure will alter the flow of only those indented statements.

if-else

If the condition given in if is False, the if-else block will perform the code t=given in the else block.

Code

# Python program to show how to use the if-else control structure

# Initializing two variables

v = 4

t = 5

print("The value of v is ", v, "and that of t is ", t)

# Checking the condition

if v > t :

print("v is greater than t")

# Giving the instructions to perform if the if condition is not true

else :

print("v is less than t")

Repetition

To repeat a certain set of statements, we use the repetition structure.

There are generally two loop statements to implement the repetition structure:

• The for loop

• The while loop

Python Functions is a block of statements that return the specific task. The idea is to put some commonly or repeatedly done tasks together and make a function so that instead of writing the same code again and again for different inputs, we can do the function calls to reuse code contained in it over and over again.

Some Benefits of Using Functions

Increase Code Readability

Increase Code Reusability

Creating a Function in Python

We can define a function in Python, using the def keyword. We can add any type of functionalities and properties to it as we require. By the following example, we can understand how to write a function in Python. In this way we can create Python function definition by using def keyword.

Python3

# A simple Python function

def fun():

    print("Welcome to GFG")

Calling a Function in Python

After creating a function in Python we can call it by using the name of the functions Python followed by parenthesis containing parameters of that particular function. Below is the example for calling def function Python.

Python3

# A simple Python function

def fun():

    print("Welcome to GFG")

# Driver code to call a function

fun()

Output:

Welcome to GFG

Python Function with Parameters

If you have experience in C/C++ or Java then you must be thinking about the return type of the function and data type of arguments. That is possible in Python as well (specifically for Python 3.5 and above).

Python Function Syntax with Parameters

def function_name(parameter: data_type) -> return_type:    """Docstring"""    # body of the function    return expression

Python programming language provides two types of Python loopshecking time. In this article, we will look at Python loops and understand their working with the help of examp – For loop and While loop to handle looping requirements. Loops in Python provides three ways for executing the loops.

While all the ways provide similar basic functionality, they differ in their syntax and condition-checking time. In this article, we will look at Python loops and understand their working with the help of examples.

While Loop in Python

In Python, a while loop is used to execute a block of statements repeatedly until a given condition is satisfied. When the condition becomes false, the line immediately after the loop in the program is executed.

count = 0

while (count < 3):

    count = count + 1

    print("Hello Geek")
output:
Hello Geek

Hello Geek

Hello Geek

For Loop in Python

For loops are used for sequential traversal. For example: traversing a list or string or array etc. In Python, there is “for in” loop which is similar to foreach loop in other languages. Let us learn how to use for loops in Python for sequential traversals with examples.

n = 4

for i in range(0, n):

    print(i)

output:

0

1

2

3