Introduction to Python

About Python

• Python is a general-purpose, high-level programming language.
• It was developed by Guido van Rossum in 1989 at the National Research Institute in the Netherlands.
• Python was officially released to the public on February 20, 1991.
• Python is highly recommended as a first programming language for beginners due to its simplicity.

---

Examples

Example 1: Print "Hello World"

Java:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

C:

#include<stdio.h>
void main() {
    printf("Hello World");
}

Python:

print("Hello World")

---

Example 2: Sum of Two Numbers

Java:

public class Add {
    public static void main(String[] args) {
        int a, b;
        a = 10;
        b = 20;
        System.out.println("The Sum: " + (a + b));
    }
}

C:

#include <stdio.h>

void main() {
    int a, b;
    a = 10;
    b = 20;
    printf("The Sum: %d", (a + b));
}

Python:

a = 10
b = 20
print("The Sum:", (a + b))

---

Origin of the Name "Python"

The name Python was inspired by the British comedy TV show "Monty Python’s Flying Circus" broadcasted by the BBC from 1969 to 1974.

---

Language Influences

Guido van Rossum designed Python by borrowing features from various programming languages:

• Functional programming: C
• Object-oriented programming: C++
• Scripting features: Perl, Shell Script
• Modular programming: Modula-3
• Syntax is mostly derived from C and ABC languages.

---

Applications of Python

Python can be used in a wide variety of areas:

1. Desktop Applications
2. Web Applications
3. Database Applications
4. Network Programming
5. Game Development
6. Data Analysis
7. Machine Learning
8. Artificial Intelligence
9. Internet of Things (IoT)

Note: Python is used by companies like Google, Microsoft, IBM, Yahoo. It's also used in YouTube, NASA, and New York Stock Exchange.

---

Features of Python

1. Simple and Easy to Learn

• Python code reads like English.
• Minimal syntax, around 30+ keywords.
• Fewer lines of code for the same logic compared to other languages.

2. Free and Open Source

• No license needed to use Python.
• Source code is open for modification (e.g., Jython for Java integration).

3. High-Level Language

• Programmer-friendly; no need to manage memory or security manually.

4. Platform Independent

• Write once, run anywhere (PVM handles platform translation).

5. Portable

• Code produces the same result across platforms.

6. Dynamically Typed

• No need to declare variable types explicitly.
• Type is inferred at runtime.

7. Supports Both Procedural and Object-Oriented Programming

8. Interpreted Language

• Compilation handled by Python Interpreter.
• Errors raised at runtime if any.

9. Extensible

• Can integrate code from other languages for performance or legacy reuse.

10. Embeddable

• Python code can be embedded within other languages.

11. Extensive Library Support

• Large standard library with built-in functions and modules.

---

Limitations of Python

1. Performance

• Slower than compiled languages due to interpretation.

2. Not Commonly Used for Mobile Development

---

Flavors of Python

Flavor	Description
CPython	Standard implementation using C
Jython/JPython	For Java applications (runs on JVM)
IronPython	For C#/.NET applications
PyPy	JIT compiler support for faster performance
RubyPython	Integrates Python with Ruby
AnacondaPython	Optimized for data processing and analytics

---

Python Versions

Version	Release Date
Python 1.0	January 1994
Python 2.0	October 2000
Python 3.0	December 2008

Note: Python 3 does not provide backward compatibility with Python 2. Python 2 programs may not run on Python 3 without modifications.

Current Common Versions:

• Python 3.6.1
• Python 2.7.13

---

76. Python Program to Differentiate Between type() and isinstance()

class Polygon:
    def sides_no(self):
        pass

class Triangle(Polygon):
    def area(self):
        pass

obj_polygon = Polygon()
obj_triangle = Triangle()

print(type(obj_triangle) == Triangle)    # true
print(type(obj_triangle) == Polygon)     # false

print(isinstance(obj_polygon, Polygon))  # true
print(isinstance(obj_triangle, Polygon)) # true

we see that type() cannot distinguish whether an instance of a class is somehow related to the base class.

• In our case, although obj_triangle is an instance of child class Triangle,
• it is inherited from the base class Polygon. If you want to relate the object of a child class with the base class,
• you can achieve this with isinstance().

80. Python Program to Return Multiple Values From a Function

# Example 1: Return values using comma
def name():
    return "John","Armin"

# print the tuple with the returned values
print(name())

# get the individual items
name_1, name_2 = name()
print(name_1, name_2)

88. Python Program to Compute the Power of a Number

1

# Calculate the power of a number using pow() function
base = 3
exponent = 4

result = pow(base, exponent)
print("Answer = " + str(result))

# Calculate power of a number using a for loop
base = 3
exponent = 4

result = 1

for exponent in range(exponent, 0, -1):
    result *= base

print("Answer = " + str(result))

# Calculate power of a number using a while loop
base = 3
exponent = 4

result = 1

while exponent != 0:
    result *= base
    exponent-=1

print("Answer = " + str(result))

base = 3
exponent = 4
exponent+=1
result =1

while exponent:=  exponent-1:
    result *= base
result

base = 3
exponent = 4
result =1

while exponent:
    result *= base
    exponent-=1

result

89. Python Program to Count the Number of Digits Present In a Number

num = 1234567

def count_digits(n):
    count = 0
    while n > 0:
        n = n // 10
        count += 1
    return count

digit_count = count_digits(abs(num)) 
print(digit_count)