basic python

1.  What is Python?
 Features of Python
 What we can do with Python?
 Companies using python today
 Installing Python
 Python as a Calculator/Arithmetic Expression

2.  Python is a VHLL (Very High Level Language).
 VHLL is designed to reduce the complexity
and to reduce amount of source code
required to create a program
 Created by Guido van Rossum (Univ. of
Amesterdam) in 1991.

3. ▪ What is a high-level programming language?
– Not interpretable or directly executable by the CPU
– Has to be translated into a low-level language (assembly
language) or the executable machine language
– E.g.: Python (C, C++, Java, Ruby, …)
▪ Advantages (as compared to low-level languages):
– Easier to implement and require shorter amount of time to
write
▪ (Very) English like
▪ More readable/comprehensible by programmers
– Portable and platform independent
▪ Programs just have to be written once but can be
run on any types of computer platform (without
much modification effort)

4. ▪ When you execute a Python program:
– Source code of your program (.py files) is compiled
(translated) into a format known as byte code
▪ Byte code is a lower-level, platform-independent
representation of the source code of your program
▪ Byte code of your programs are stored as .pyc files
in the subdirectory named pycache.
▪ Once a program has been compiled into byte code
(and whenever the byte code is loaded from the
.pyc file):
– Each of the byte code instructions will be interpreted and
executed by the runtime execution engine, Python Virtual
Machine (PVM)

5. [Source: Chapter 2, Learning Python by Mark Lutz (2013)]

6.  Python is an interpreted, interactive, object-oriented
programming language.
 Python is supported with a rich collection of
libraries or packages (i.e. ready-to-use code) to
build sophisticated programs.
 Python combines remarkable power with very clear
syntax.
 It has modules & very high level dynamic data type.

7.  System Programming
 Graphical User Interface Programming
 Database Programming
 Internet Scripting
 Gaming, Images, Robot etc.
 Data Analytics

8.  Google (web search system)
 Cisco, Intel & IBM (hardware testing)
 YouTube (video sharing services)
 NASA(Scientific Calculations)

9.  Available freely for most operating system on:
https://www.python.org/
 Available currently in two versions:
 Python 2.x & Python 3.x
 What are the differences:
Python 2.x is the status quo
Python 3.x is the present and the future of
the language
 Which version should I use:
i) If you are working on a new, fully independent
project, you can use 3.x
ii)If your work has dependencies it is safer to use
2.x...

10.  IDLE is a simple Python integrated
development environment available for
Windows, Linux, and Mac OS X.
 IDLE has a built in editor.
 You may type the above one line Python
program directly into IDLE and press enter to
execute the program.

12. Python can be used as a simple calculator:
>>> 2+1
>>> 3
>>> 4-1
>>> 3
>>> 2*2
4
>>> 12/3
4

13. >>> n = 1
>>> z = 2*n
>>> z
>> >2
OR
>>> print (z)
2
OR
>>> print(“Value of z=“,z)
>>> Value of z=2

14. The available arithmetic operators are:
Operator Stands for Precedence
+ sum 0
- subtraction 0
* multiplication 1
/ division 1
// integer division 1
% remainder 1
** power 2

15.  Python evaluates arithmetic expressions according
to precedence:
>>> 8//3
>>> 2
>>> 5%2
>>> 1
>>> 2**3
>>> 8
>>> print (8//3+5%2+2**3)
11

16.  Python has a limited knowledge of mathematical
functions.
 There is however a module, math, that extends
that: sqrt, factorial, pow, etc...
For example:
>>> import math
>>> math.sqrt(25))
5
OR
>>> from math import sqrt
>>> sqrt(25)
5

17.  Python also handles complex numbers:
Imaginary numbers are written with the suffix j or J.
Complex number have the form (real+imag j) or
with complex(real,imag)

18.  Complex number have the form (real+imag j)
 A complex number z has a real part and an
imaginary part, which are accessible with
z.real and z.imag.
>>> z = 3.0+4.0j
>>> z.real
3.0
>>> z.imag
4.0

19. Structure of a Python program:
 Programs are composed of modules.
 Modules contain statements(instructions) and
expressions.
 Instructions and expressions create and
process objects.

20. Objects correspond to a certain memory
region to which a unique memory address is
associated and in which we store:
 Data,
 Information about the data,
 Functions that act upon the data.

21. For example:
>>> x = 123
 creates the object 123, somewhere in
memory and gives it the name x.
 We can also say that x “is reference to” the
object or even that “it points to” the object.

22. We can easily obtain the type and unique memory
address for an object:
>>> x = 1.2
>>> print(x)
1.2
>>> type(x)
<type float>
>>> id(x)
135625436

23. It is possible to give more than one name to
an object. This is called aliasing:
>>> x = 45
>>> y = 45
>>> id(x)
135363888
>>> id(y)
135363888

24. We can even do aliasing in just one go:
>>> x = y = 45
>>> id(x)
135363888
>>> id(y)
135363888

25. Thanks