Lesson01 Introduction
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wangombeerick2005Lesson01 Introduction
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wangombeerick2005Lesson 1: Introduction
Python is a high-level, interpreted, interactive and object-oriented
programming language. Python is designed to be highly readable. It uses
English keywords frequently whereas the other languages use punctuations. It
has fewer syntactical constructions than other languages
The current version of Python (3.x) was released in 2008. This version is not
compatible with the prior version (2.x). This course will be based on the syntax
of Python version 3.x.
Interpreted: Python is processed at runtime by the interpreter. You do not
need to compile your program before executing it. This is similar to PERL and
PHP.
Interactive: You can actually sit at a Python prompt and interact with the
interpreter directly to write your programs.
Object-Oriented: Python supports Object-Oriented style or technique of
programming that encapsulates code within objects.
Python's features include-
Easy-to-learn: Python has few keywords, simple structure, and a clearly
defined syntax. This allows a student to pick up the language quickly.
Easy-to-read: Python code is more clearly defined and visible to the
eyes.
Easy-to-maintain: Python's source code is fairly easy-to-maintain.
A broad standard library: Python's bulk of the library is very portable
and cross- platform compatible on UNIX, Windows, and Macintosh.
Interactive Mode: Python has support for an interactive mode, which
allows interactive testing and debugging of snippets of code.
Portable: Python can run on a wide variety of hardware platforms and
has the same interface on all platforms.
Extendable: You can add low-level modules to the Python interpreter.
These modules enable programmers to add to or customize their tools to
be more efficient.
Databases: Python provides interfaces to all major commercial
databases.
GUI Programming: Python supports GUI applications that can be
created and ported to many system calls, libraries and windows systems,
such as Windows MFC, Macintosh, and the X Window system of Unix.
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Scalable: Python provides a better structure and support for large
programs than shell scripting.
Apart from the above-mentioned features, Python has a big list of good
features. A few are listed below-
It supports functional and structured programming methods as well as
OOP.
It can be used as a scripting language or can be compiled to byte code for
building large applications.
It provides very high-level dynamic data types and supports dynamic type
checking.
It supports automatic garbage collection.
It can be easily integrated with C, C++, COM, ActiveX, CORBA, and Java.
Installing Python
Discuss in groups and find out the best way / form of python installation
Starting Python
There are three different ways to start Python-
1. Interactive Interpreter
You can start Python from a command-line interpreter or shell window. This is
achieved by executing the python command from a shell prompt. Then you
can start coding right away using the interactive interpreter.
2. Script from the Command-line
A Python script can be executed at the command line by invoking the
interpreter on your application. Eg C:>python test.py # Windows/DOS
While on Linux /Unix platforms always ensure the file permission mode allows
execution.
3. Integrated Development Environment
You can run Python from a Graphical User Interface (GUI) environment as well,
if you have a GUI application on your system that supports Python. Examples
are PyCharm, Visual Studio Code, Sublime Text, Vim, Atom, Jupyter
Notebook, Eclipse + PyDev + LiClipse, GNU Emacs, Spyder, Thonny.
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Identifiers
A Python identifier is a name used to identify a variable, function, class,
module or other object. An identifier starts with a letter A to Z or a to z or an
underscore (_) followed by zero or more letters, underscores and digits (0 to
9). Punctuation characters such as @, $, and % are not allowed within
identifiers. Python is a case sensitive programming language.
Here are naming conventions for Python identifiers-
• Class names start with an uppercase letter. All other identifiers start
with a lowercase letter.
• Starting an identifier with a single leading underscore indicates that the
identifier is private.
• Starting an identifier with two leading underscores indicates a strong
private identifier.
• If the identifier also ends with two trailing underscores, the identifier is a
language- defined special name.
Reserved Words
and, as, assert, break, class, continue, def, del
elif, else, except, exec, finally, for, from, global,
if, import, in, is, lambda, not, or, pass,
print, raise, return, try, while, with, yield
Indentation / Blocks
Python does not use braces ({}) to indicate blocks of code for class and
function definitions or flow control. Blocks of code are denoted by line
indentation, which is rigidly enforced.
gender="Male"
if gender=="Male":
print ("Gender is Male")
print ("do something …")
else:
print ("Not Male")
print ("do a different …")
Quotations
Single, double, and triple (''' or """) quotes are used to denote string literals,
as long as the same type of quote starts and ends the string. Eg.
word = 'word'
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sentence = "This is a sentence."
paragraph = """This is a paragraph. It is made up of multiple lines and
sentences."""
Comments
A hash sign (#) that is not inside a string literal is the beginning of a comment.
All characters after the #, up to the end of the physical line, are part of the
comment and the Python interpreter ignores them.
e.g. # My First comment
Statements
Statements in Python typically end with a new line. The semicolon (;) allows
multiple statements on a single line. The line continuation character (\) allows
one statement to break to the next line. However, statements contained within
the [], {}, or () brackets do not need to use the line continuation character.
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