GE8161 PROBLEM SOLVING AND PYTHON PROGRAMMING LABORATORY Manual

Notes 71 Pages

Anna University

Computer Engineering

Contributed by

Yash Baria

1

INTRODUCTION
TO
PYTHON PROGRAMMING
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Expt: 1
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INTRODUCTION TO PYTHON
History of Python
The programming language Python was conceived in the late 1980s, and its implementation was started in
December 1989 by Guido van Rossum at CWI in the Netherlands as a successor to the ABC
(programming language) capable of exception handling and interfacing with the Amoeba operating
system. Van Rossum is Python's principal author, and his continuing central role in deciding the direction
of Python is reflected in the title given to him by the Python community, Benevolent Dictator for Life
(BDFL). Python was named for the BBC TV show Monty Python's Flying Circus.
Python 2.0 was released on October 16, 2000, with many major new features, including a cycle- detecting
garbage collector (in addition to reference counting) for memory management and support for Unicode.
However, the most important change was to the development process itself, with a shift to a more
transparent and community-backed process.
Python 3.0, a major, backwards-incompatible release, was released on December 3, 2008 after a long
period of testing. Many of its major features have also been backported to the backwards- compatible
Python 2.6 and 2.7.
Early history
In February 1991, van Rossum published the code (labeled version 0.9.0) to alt.sources.Already present at
this stage in development were classes with inheritance, exception handling, functions,
and the core datatypes of list , dict , and so on. Also in this initial release was a module
system borrowed from Modula-3; Van Rossum describes the module as "one of Python's major programming
units".
[1]
Python's exception model also resembles Modula-3's, with the addition of
an clause.
[3]
In 1994 comp.lang.python, the primary discussion forum for Python, was
formed, marking a milestone in the growth of Python's userbase.
Version
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filter
Python reached version 1.0 in January 1994. The major new features included in this release
were the functional programming tools lambda , map , and reduce . Van Rossum stated

that "Python acquired lambda, reduce(), filter() and map(), courtesy of a Lisp hacker who missed them
and submitted working patches".
The last version released while Van Rossum was at CWI was Python 1.2. In 1995, Van Rossum continued
his work on Python at the Corporation for National Research Initiatives(CNRI) in Reston, Virginia
whence he released several versions.
By version 1.4, Python had acquired several new features. Notable among these are the Modula- 3
inspired keyword arguments (which are also similar to Common Lisp's keyword arguments) and built-in
support for complex numbers. Also included is a basic form of data hiding by name mangling, though this
is easily bypassed.
During Van Rossum's stay at CNRI, he launched the Computer Programming for Everybody (CP4E)
initiative, intending to make programming more accessible to more people, with a basic "literacy" in
programming languages, similar to the basic English literacy and mathematics skills required by most
employers. Python served a central role in this: because of its focus on clean syntax, it was already
suitable, and CP4E's goals bore similarities to its predecessor, ABC. The project was funded by DARPA.
As of 2007, the CP4E project is inactive, and while Python attempts to be easily learnable and not too
arcane in its syntax and semantics, reaching out to non-programmers is not an active concern.
BeOpen

In 2000, the Python core development team moved to BeOpen.com to form the BeOpen
PythonLabs team. CNRI requested that a version 1.6 be released, summarizing Python's development up
to the point at which the development team left CNRI. Consequently, the release schedules for 1.6 and 2.0
had a significant amount of overlap. Python 2.0 was the only release from BeOpen.com. After Python 2.0
was released by BeOpen.com, Guido van Rossum and the other PythonLabs developers joined Digital
Creations.
The Python 1.6 release included a new CNRI license that was substantially longer than the CWI license
that had been used for earlier releases. The new license included a clause stating that the
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license was governed by the laws of the State of Virginia. The Free Software Foundation argued that the
choice-of-law clause was incompatible with the GNU General Public License. BeOpen, CNRI and the
FSF negotiated a change to Python's free software license that would make it GPL-compatible. Python
1.6.1 is essentially the same as Python 1.6, with a few minor bug fixes, and with the new GPL-compatible
license
Version 2
Python 2.0 introduced list comprehensions, a feature borrowed from the functional programming
languages SETL and Haskell. Python's syntax for this construct is very similar to Haskell's, apart from
Haskell's preference for punctuation characters and Python's preference for alphabetic keywords. Python
2.0 also introduced a garbage collection system capable of collecting reference cycles.
Python 2.1 was close to Python 1.6.1, as well as Python 2.0. Its license was renamed Python Software
Foundation License. All code, documentation and specifications added, from the time of Python 2.1's
alpha release on, is owned by the Python Software Foundation (PSF), a non- profit organization formed in
2001, modeled after the Apache Software Foundation. The release included a change to the language
specification to support nested scopes, like other statically scoped languages. (The feature was turned off
by default, and not required, until Python 2.2.)
A major innovation in Python 2.2 was the unification of Python's types (types written in C) and classes
(types written in Python) into one hierarchy. This single unification made Python's object model purely
and consistently object oriented. Also added were generators which were inspired by Icon.
Python 2.6 was released to coincide with Python 3.0, and included some features from that release, as
well as a "warnings" mode that highlighted the use of features that were removed in Python 3.0.Similarly,
Python 2.7 coincided with and included features from Python 3.1,which was released on June 26, 2009.
Parallel 2.x and 3.x releases then ceased, and Python 2.7 was the last release in the 2.x series. In
November 2014, it was announced that Python 2.7 would be supported until 2020, but users were
encouraged to move to Python 3 as soon as possible.
Version 3
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Python 3.0 (also called "Python 3000" or "Py3K") was released on December 3, 2008.It was designed to
rectify fundamental design flaws in the language—the changes required could not be implemented while
retaining full backwards compatibility with the 2.x series, which necessitated a new major version
number. The guiding principle of Python 3 was: "reduce feature duplication by removing old ways of
doing things".
Python 3.0 was developed with the same philosophy as in prior versions. However, as Python had
accumulated new and redundant ways to program the same task, Python 3.0 had an emphasis on removing
duplicative constructs and modules, in keeping with "There should be one— and preferably only one —
obvious way to do it".
Nonetheless, Python 3.0 remained a multi-paradigm language. Coders still had options among object-
orientation, structured programming, functional programming and other paradigms, but within such broad
choices, the details were intended to be more obvious in Python 3.0 than they were in Python 2.x.
Compatibility
Python 3.0 broke backward compatibility, and much Python 2 code does not run unmodified on Python 3.
Python's dynamic typing combined with the plans to change the semantics of certain methods of
dictionaries, for example, made perfect mechanical translation from Python 2.x to Python 3.0 very
difficult. A tool called "2to3" does the parts of translation that can be done automatically. At this, 2to3
appeared to be fairly successful, though an early review noted that there were aspects of translation that
such a tool would never be able to handle.Prior to the roll- out of Python 3, projects requiring
compatibility with both the 2.x and 3.x series were recommended to have one source (for the 2.x series),
and produce releases for the Python 3.x platform using 2to3. Edits to the Python 3.x code were
discouraged for so long as the code needed to run on Python 2.x.This is no longer recommended; as of
2012 the preferred alternative is to create a single code base that can run under both Python 2 and 3 using
compatibility modules.
Features of Python

a) Simple
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Python is a simple and minimalistic language. Reading a good Python program feels almost like reading
English (but very strict English!). This pseudo-code nature of Python is one of its greatest strengths. It
allows you to concentrate on the solution to the problem rather than the syntax i.e. the language itself.

b) Easy to Learn

As you will see, Python is extremely easy to get started with. Python has an extraordinarily simple syntax
as already mentioned.

c) Free and Open Source

Python is an example of a FLOSS (Free/Libre and Open Source Software). In simple terms, you can
freely distribute copies of this software, read the software's source code, make changes to it, use pieces of
it in new free programs, and that you know you can do these things. FLOSS is based on the concept of a
community which shares knowledge. This is one of the reasons why Python is so good - it has been
created and improved by a community who just want to see a better Python.

d) High-level Language

When you write programs in Python, you never need to bother about low-level details such as managing
the memory used by your program.

e) Portable

Due to its open-source nature, Python has been ported (i.e. changed to make it work on) to many many
platforms. All your Python programs will work on any of these platforms without requiring any changes
at all. However, you must be careful enough to avoid any system- dependent features.

You can use Python on Linux, Windows, Macintosh, Solaris, OS/2, Amiga, AROS, AS/400, BeOS,
OS/390, z/OS, Palm OS, QNX, VMS, Psion, Acorn RISC OS, VxWorks, PlayStation, Sharp Zaurus,
Windows CE and PocketPC !
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f) Interpreted

This requires a little explanation.

A program written in a compiled language like C or C++ is translated from the source language
i.e. C/C++ into a language spoken by your computer (binary code i.e. 0s and 1s) using a compiler with
various flags and options. When you run the program, the linker/loader software just stores the binary
code in the computer's memory and starts executing from the first instruction in the program.

When you use an interpreted language like Python, there is no separate compilation and execution steps.
You just run the program from the source code. Internally, Python converts the source code into an
intermediate form called bytecodes and then translates this into the native language of your specific
computer and then runs it. All this makes using Python so much easier. You just run your programs - you
never have to worry about linking and loading with libraries, etc. They are also more portable this way
because you can just copy your Python program into another system of any kind and it just works!

g) Object Oriented

Python supports procedure-oriented programming as well as object-oriented programming. In
procedure-oriented languages, the program is built around procedures or functions which are nothing but
reusable pieces of programs. In object-oriented languages, the program is built around objects which
combine data and functionality. Python has a very powerful but simple way of doing object-oriented
programming, especially, when compared to languages like C++ or Java.

h) Extensible

If you need a critical piece of code to run very fast, you can achieve this by writing that piece of code in
C, and then combine that with your Python program.
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i) Embeddable

You can embed Python within your C/C++ program to give scripting capabilities for your program's
users.

j) Extensive Libraries

The Python Standard Library is huge indeed. It can help you do various things involving regular
expressions, documentation generation, unit testing, threading, databases, web browsers, CGI, ftp, email,
XML, XML-RPC, HTML, WAV files, cryptography, GUI(graphical user interfaces) using Tk, and also
other system-dependent stuff. Remember, all this is always available wherever Python is installed. This is
called the "batteries included" philosophy of Python.

Besides the standard library, there are various other high-quality libraries such as the Python Imaging
Library which is an amazingly simple image manipulation library.

Version release dates

Release dates for the major and minor versions:



Python 1.0 - January 1994


Python 1.5 - December 31, 1997


Python 1.6 - September 5, 2000


Python 2.0 - October 16, 2000


Python 2.1 - April 17, 2001


Python 2.2 - December 21, 2001


Python 2.3 - July 29, 2003


Python 2.4 - November 30, 2004


Python 2.5 - September 19, 2006


Python 2.6 - October 1, 2008


Python 2.7 - July 3, 2010
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

Python 3.0 - December 3, 2008


Python 3.1 - June 27, 2009


Python 3.2 - February 20, 2011


Python 3.3 - September 29, 2012


Python 3.4 - March 16, 2014


Python 3.5 - September 13, 2015


Python 3.6 - December 23, 2016
Python is a widely used high-level programming language for general-purpose programming, created
by Guido van Rossum and first released in 1991.

Python is a general purpose programming language created in the late 1980s, and named after Monty
Python, that's used by thousands of people to do things from testing microchips at Intel, to powering
Instagram, to building video games with the PyGame library.

Python is a programming language. It's used for many different applications. It's used in some high
schools and colleges as an introductory programming language because Python is easy to learn, but it's
also used by professional software developers at places such as Google, NASA, and Lucasfilm Ltd.

When he began implementing Python, Guido van Rossum was also reading the published scripts from
“Monty Python's Flying Circus”, a BBC comedy series from the 1970s. Van Rossum thought he needed
a name that was short, unique, and slightly mysterious, so he decided to call the language Python.

The Python programming language was conceived in the late 1980s, and its implementation was started
in December 1989 by Guido van Rossum at CWI in the Netherlands as a successor to the ABC
programming language capable of exception handling and interfacing with the Amoeba operating system.
Python on a Macintosh running Mac OS X is in principle very similar to Python on any other Unix
platform, but there are a number of additional features such as the IDE and the Package Manager that are
worth pointing out. The Mac-specific modules are documented in Mac OS X specific services.

9
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Python is a high-level programming language designed to be easy to read and simple to implement. It is
open source, which means it is free to use, even for commercial applications. Python is considered a
scripting language, like Ruby or Perl and is often used for creating Web applications and dynamic Web
content

Python is a widely used high-level programming language for general-purpose programming, created by
Guido van Rossum and first released in 1991. CPython, the reference implementation of Python, is open
source software and has a community-based development model, as do nearly all of its variant
implementations

Python is used in GIS programming. It is used as a scripting language for ArcGIS, and for Quantum GIS.
Python is true general purpose language. Your question is kind of like asking, what area should you focus
on if you want C++ job or Java job.

Learning Python is really easy, a breeze if you've learned other object oriented programming languages.
... It's recommended to be the first language people learn as it contains all the OO concepts but is easier
to read and less strongly typed as C++ or to a lesser extent Java.

Apart from Windows, Linux and MacOS, CPython implementation runs on 21 different platforms.
IronPython is a .NET framework based Python implementation and it is cabable of running in both
Windows, Linux and in other environments where .NET framework is available.
Python is, or can be used as the scripting language in these software products:


Abaqus (Finite Element Software)


Advantage Framework.


Amarok.


ArcGIS, a prominent GIS platform, allows extensive modeling using Python.


Autodesk Maya, professional 3D modeler allows Python scripting as an alternative to MEL as of version
8.5.
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GE8161 PROBLEM SOLVING AND PYTHON PROGRAMMING LABORATORY Manual

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