CBSE Class 12 Computer Science

## What Python is Python is a high-level, general-purpose programming language. It is **interpreted**, which means a program is translated and run one statement at a time by the Python interpreter rather than being compiled to a separate machine-code file first. It is **dynamically typed**, so a variable has no declared type and takes the type of whatever value it currently refers to. It is free and open source, runs on Windows, Linux and macOS without changes to the program, and has a large library of ready-made modules. Python is case-sensitive, so `Total` and `total` are two different names, and it uses indentation, not braces, to mark where a block of statements begins and ends. ## Execution modes Python can be used in two ways. In **interactive mode** each statement is typed at the `>>>` prompt and executed at once, and the result of an expression is shown straight away. This suits trying out a single idea, but nothing is saved. ```python >>> 6 * 7 42 >>> print("hello") hello ``` In **script mode** the statements are written in a file saved with the extension `.py`, and the whole file is run. The value of a bare expression is not printed in a script, so `print()` is needed to show output. A first program is one line: ```python print("Hello, world") ``` ## Python character set and tokens The character set is the group of characters Python recognises: letters, digits, special symbols such as `+ - * / % ( ) [ ] { } , : ; .`, white space (space, tab, newline) and other…