What is Python? — Why is it so popular?

After completing this topic

You will be able to explain what Python is and why it is used in so many fields.

The most popular language in the world

In the rankings of programming language popularity (TIOBE, Stack Overflow survey), Python consistently ranks 1st or 2nd every year. From introductory courses at universities to data analysis, AI research, web servers, and automation scripts, Python is everywhere.

Why is that?

Easy to read

The biggest advantage of Python is that the code is easy to read, like English.

# Another language (Java)
if (score >= 90) {
    System.out.println("A grade");
}

# Python
if score >= 90:
    print("A grade")

It uses indentation to separate blocks of code, without curly braces ({}). There are no semicolons (;) either. Even beginners can immediately understand "what this means."

Interpreted language

Python is an interpreted language. You can execute the code line by line.

# Enter the interactive mode by typing python3 in the terminal
>>> 2 + 3
5
>>> "hello" * 3
'hellohellohello'
>>> len("Python")
6

Since compilation (converting source code → executable file) is not required, you can immediately check the results as you write. It is ideal for experimenting and learning.

Dynamic typing

You do not declare the type when creating a variable.

# Use it directly without type declaration
name = "Kim Hoon"        # String
age = 30             # Integer
pi = 3.14            # Float
is_student = True    # Boolean

# You can also put a different type in the same variable
x = 10
x = "Now a string"    # No error

It is flexible, but in large programs, it can be difficult to keep track of "what is in this variable." Therefore, type hints were introduced in Python 3.5 (not enforced).

Library ecosystem

The reason Python is so powerful is its libraries.

"I want to do this" → pip install library_name → use it immediately. Tasks that would take hundreds of lines in other languages can be done in a few lines in Python.

# Example: Fetching a web page
import requests
response = requests.get("https://example.com")
print(response.status_code)  # 200

Weaknesses of Python

It is not all-powerful:

For speed-critical operations, libraries written in C (numpy, PyTorch) handle the processing. It has a structure where "Python directs, and C executes."

Where to start

# Check if it is installed
python3 --version

# Start interactive mode
python3

# Run from a file
python3 hello.py

It is likely already installed (macOS, Linux). On Windows, download it from python.org.