Getting Started with Python

Computers execute only machine language, which is difficult for humans to write. High-level languages such as C, C++, Java and Python were developed because they are easier for humans to use. Programs in them must be converted to machine language by translators.

Python uses an interpreter that translates and executes code line by line. When a program is run, the source code is first converted into bytecode, which the Python interpreter then executes.

• It is a low-level set of instructions that the Python interpreter can understand.
• It is not machine code and cannot run directly on hardware.
• It is platform independent, so the same program can run on different systems.
• It helps programs execute faster by avoiding repeated compilation.

Python was developed by Guido van Rossum, a Dutch computer programmer, who began working on it in the late 1980s. The first official version, Python 0.9.0, was released in 1991. He named it after the British comedy group Monty Python's Flying Circus, as he was a fan of the show and thought the name was short, memorable and a bit quirky.

• Simple syntax: code looks almost like plain English, easy to read, write and understand.
• Libraries and frameworks: a vast collection of reusable tools.
• Cross-platform: runs on Windows, Mac and Linux without significant modification.
• Open source: source code is free to use, modify and distribute; improved by a global community.
• Concise: usually needs fewer lines of code than C++ or Java.
• Versatile: used in web development, data science, automation, AI and more.

A library is a reusable collection of functions, classes and modules designed for specific tasks such as mathematical data handling, graphics or networking.

A framework provides a complete structure for developing software applications. Examples: Django and Flask (web development); Pandas, TensorFlow and Scikit-learn (AI, machine learning and data science).

Its source code is freely available for anyone to use, modify and distribute. This makes Python cost-free, highly flexible and continuously improved by a large global community.

Python code can run on multiple operating systems, including Windows, Mac and Linux, without requiring significant modifications.

An Integrated Development Environment is a software application that provides a comprehensive platform for writing, debugging and testing code. It enhances productivity, simplifies development and improves code quality.

No. You may use any suitable IDE to write the program, but a Python interpreter must be installed on the computer to run it.

IDLE version 3.10.12 with GNU Linux 22.04.5 LTS.

• Press the Super key to launch the search bar on the desktop.
• Type "idle" (upper or lower case) in the search bar.
• Click the IDLE icon to open the IDLE Shell.

The symbol >>> is the Python prompt. It indicates that the interpreter is ready to execute instructions.

Interactive mode and script mode.

Interactive mode executes individual statements instantly and gives immediate results. A statement is typed at the >>> prompt and Enter is pressed; the result appears on the next line and the prompt reappears.

>>> print("Hello World!!")
Hello World!!
>>> print(5+2)
7
>>> (12+5)/2
8.5

In interactive mode, arithmetic expressions such as addition, subtraction, multiplication and division can be typed at the prompt. On pressing Enter the result is shown, e.g. (12+5)/2 gives 8.5.

The code cannot be saved for later use. To run the same code again it must be retyped. Script mode overcomes this.

In script mode, a program containing more than one instruction is written in a file, saved, executed, and edited as needed. Python files are saved with the extension .py, by default in the current working directory (e.g. /home/linux/).

• Choose File → New File (or press Ctrl+N).
• Type the Python statements in the new file.
• Save with a suitable name and the .py extension (e.g. test.py).
• Run with Run → Run Module (or press F5).
• The output appears in the Python shell.

Hello World!!
7
14.5

The last line follows operator precedence: 5/2 = 2.5 is calculated first, then 12 + 2.5 = 14.5.

print() displays a message or the result of an expression on the screen, e.g. print("Hello World!!") shows Hello World!!.

Welcome to Python programming
37
HelloWorld

• It displays whatever is given inside its brackets.
• Text in quotation marks is printed exactly as written, without the quotes.
• An expression such as 25 + 12 is evaluated first and only the result (37) is printed.
• Each print() starts its output on a new line.

With numbers, + performs arithmetic addition (25 + 12 gives 37). With text (strings), + joins them together, called concatenation ("Hello" + "World" gives HelloWorld, with no space added). So the same operator behaves differently depending on the type of data.

Radius = diameter / 2 = 6 cm; area = π r².

print(3.14 * (12/2) * (12/2))

Output: 113.04 (square cm).

Perimeter = 2 × (length + breadth).

print(2 * (7 + 5))

Output: 24 (cm).

• Python uses an ______ to translate code: interpreter.
• The Python prompt is ______: >>>.
• Python files have the extension ______: .py.
• The shortcut to run a module in IDLE is ______: F5.
• The shortcut to create a new file in IDLE is ______: Ctrl+N.