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Define python?

Python is simple and easy to learn language compared to other programming languages. Python was introduced to the world in the year 1991 by Guido van Rossum. It is a dynamic object oriented language used for developing software. It supports various programming languages and have a massive library support for many other languages. It is a modern powerful interpreted language with objects, modules, threads, exceptions, and automatic memory managements.

Salient features of Python are

-Simple & Easy: Python is simple language & easy to learn.

-Free/open source: it means everybody can use python without purchasing license.

-High level language: when coding in Python one need not worry about low-level details.

-Portable: Python codes are Machine & platform independent.

-Extensible: Python program supports usage of C/ C++ codes.

-Embeddable Language: Python code can be embedded within C/C++ codes & can be used a scripting language.

-Standard Library: Python standard library contains prewritten tools for programming.

-Build-in Data Structure: contains lots of data structure like lists, numbers & dictionaries.

python 2013-12-28 09:00:56

Define a method in Python?

A function on object x is a method which is called as x.name(argumentsâ€¦). Inside the definition of class, methods are defined as functions:

class C:

def meth(self, atg):

return arg*2+self.attribute

python 2013-12-28 09:02:39

Define self?

'self' is a conventional name of methodâ€™s first argument. A method which is defined as meth(self, x ,y ,z) is called as a.meth(x, y, z) for an instance of a class in which definition occurs and is called as meth(a, x ,y, z).

python 2013-12-28 09:05:03

Describe python usage in web programming?

Python is used perfectly for web programming and have many special features to make it easy to use. Web frame works, content management systems, WebServers, CGI scripts, Webclient programming, Webservices, etc are the features supported by python. Python language is used to create various high end applications because of its flexibility.

python 2013-12-28 09:05:36

Is there any tool used to find bugs or carrying out static analysis?

Yes. PyChecker is the static analysis tool used in python to find bugs in source code, warns about code style and complexity etc. Pylint is a tool that verifies whether a module satisfies standards of coding and makes it possible to add custom feature and write plug-ins.

python 2013-12-28 09:18:25

Rules for local and global variables in python?

In python, the variables referenced inside a function are global. When a variable is assigned new value anywhere in the body of a function then it is assumed as local. In a function, if a variable ever assigned new value then the variable is implicitly local and explicitly it should be declared as global. If all global references require global then you will be using global at anytime. Youâ€™d declare as global each reference to built-in function or to component of module which is imported. The usefulness of global declaration in identifying side-effects is defeated by this clutter.

python 2013-12-28 09:37:01

How to find methods or attributes of an object?

Built-in dir() function of Python ,on an instance shows the instance variables as well as the methods and class attributes defined by the instanceâ€™s class and all its base classes alphabetically. So by any object as argument to dir() we can find all the methods & attributes of the objectâ€™s class.

Following code snippet shows dir() at work :

class Employee:

def __init__(self,name,empCode,pay):

self.name=name

self.empCode=empCode

self.pay=pay

print("dir() listing all the Methods & attributes of class Employee")

print dir(e)

-----------------------------------------------------

Output

dir() listing all the Methods & attributes of class Employee

[ '__init__', 'empCode', 'name', 'pay']

python 2013-12-28 09:37:28

Is there any equivalent to scanf() or sscanf()?

No. Usually, the easy way to divide line into whitespace-delimited words for simple input parsing use split() method of string objects. Then, decimal strings are converted to numeric values using float() or int(). An optional â€œsepâ€ parameter is supported by split() which is useful if something is used in the place of whitespace as separator. For complex input parsing, regular expressions are powerful then sscanf() of C and perfectly suits for the task.

python 2013-12-28 10:01:00

Define class?

Class is a specific object type created when class statement is executed. To create instances objects, class objects can be used as templates which represent both code and data specific to datatype. In general, a class is based on one or many classes known as base classes. It inherits methods and attributes of base classes. An object model is now permitted to redefine successively using inheritance. Basic accessor methods are provided by generic Mailbox for subclasses and mailbox like MaildirMailbox, MboxMailbox, OutlookMailbox which handle many specific formats of mailbox.

python 2013-12-28 10:01:23

How to prevent blocking in content() method of socket?

Commonly, select module is used to help asynchronous I/O.

python 2013-12-28 10:01:47

In python, are there any databases to DB packages?

Yes. Bsddb package is present in Python 2.3 which offers an interface to BerkeleyDatabase library. It Interface to hashes based on disk such as GDBM and DBM are included in standard python.

python 2013-12-28 10:03:04

How do we share global variables across modules in Python?

We can create a config file & store the entire global variable to be shared across modules or script in it. By simply importing config, the entire global variable defined it will be available for use in other modules.

For example I want a, b & c to share between modules.

config.py :

a=0

b=0

c=0

module1.py:

import config

config.a = 1

config.b =2

config.c=3

print â€œ a, b & resp. are : â€œ , config.a, config.b, config.c

------------------------------------------------------------------------

output of module1.py will be

1 2 3

python 2013-12-28 10:03:47

How can we pass optional or keyword parameters from one function to another in Python?

Gather the arguments using the * and ** specifiers in the functionâ€™s parameter list. This gives us positional arguments as a tuple and the keyword arguments as a dictionary. Then we can pass these arguments while calling another function by using * and **:

def fun1(a, *tup, **keywordArg):

...

keywordArg['width']='23.3c'

...

Fun2(a, *tup, **keywordArg)

python 2013-12-28 10:28:28

Explain pickling and unpickling.

Pickle is a standard module which serializes & de-serializes a python object structure. Pickle module accepts any python object converts it into a string representation & dumps it into a file(by using dump() function) which can be used later, process is called pickling. Whereas unpickling is process of retrieving original python object from the stored string representation for use.

python 2013-12-28 10:39:07

Explain how python is interpreted.

Python program runs directly from the source code. Each type Python programs are executed code is required. Python converts source code written by the programmer into intermediate language which is again translated it into the native language / machine language that is executed. So Python is an Interpreted language.

python 2013-12-28 10:39:40

How is memory managed in python?

Memory management in Python involves a private heap containing all Python objects and data structures. Interpreter takes care of Python heap and that the programmer has no access to it. The allocation of heap space for Python objects is done by Python memory manager. The core API of Python provides some tools for the programmer to code reliable and more robust program. Python also has a build-in garbage collector which recycles all the unused memory. When an object is no longer referenced by the program, the heap space it occupies can be freed. The garbage collector determines objects which are no longer referenced by the sprogram frees the occupied memory and make it available to the heap space. The gc module defines functions to enable /disable garbage collector:

gc.enable() -Enables automatic garbage collection.

gc.disable() - Disables automatic garbage collection.

python 2013-12-28 10:40:19

Explain indexing and slicing operation in sequences

Different types of sequences in python are strings, Unicode strings, lists, tuples, buffers, and xrange objects. Slicing & indexing operations are salient features of sequence. indexing operation allows to access a particular item in the sequence directly ( similar to the array/list indexing) and the slicing operation allows to retrieve a part of the sequence. The slicing operation is used by specifying the name of the sequence followed by an optional pair of numbers separated by a colon within square brackets say S[startno.:stopno]. The startno in the slicing operation indicates the position from where the slice starts and the stopno indicates where the slice will stop at. If the startno is ommited, Python will start at the beginning of the sequence. If the stopno is ommited, Python will stop at the end of the sequence..

Following code will further explain indexing & slicing operation:

>>> cosmeticList =[â€˜lipsstickâ€™,â€™facepowderâ€™,eyelinerâ€™,â€™blusherâ€™,kajalâ€™]

>>> print â€œSlicing operation :â€,cosmeticList[2:]

Slicing operation :[â€˜eyelinerâ€™,â€™blusherâ€™,kajalâ€™]

>>>print â€œIndexing operation :â€,cosmeticList[0]

â€œIndexing operation :lipsstick

python 2013-12-30 10:21:54

What are uses of lambda?

It used to create small anonymous functions at run time. Like e.g.

def fun1(x):

return x**2

print fun1(2)

it gives you answer 4

the same thing can be done using

sq=lambda x: x**2

print sq(2)

it gives the answer 4

python 2013-12-30 10:23:57

When do you use list vs. tuple vs. dictionary vs. set?

List and Tuple are both ordered containers. If you want an ordered container of constant elements use tuple as tuples are immutable objects.

python 2013-12-30 10:24:39

Explain how to make Forms in python.

As python is scripting language forms processing is done by Python. We need to import cgi module to access form fields using FieldStorage class.

Every instance of class FieldStorage (for â€˜formâ€™) has the following attributes:

form.name: The name of the field, if specified.

form.filename: If an FTP transaction, the client-side filename.

form.value: The value of the field as a string.

form.file: file object from which data can be read.

form.type: The content type, if applicable.

form.type_options: The options of the â€˜content-typeâ€™ line of the HTTP request, returned as a dictionary.

form.disposition: The field â€˜content-dispositionâ€™; None if unspecified.

form.disposition_options: The options for â€˜content-dispositionâ€™.

form.headers: All of the HTTP headers returned as a dictionary.

A code snippet of form handling in python:

import cgi

form = cgi.FieldStorage()

if not (form.has_key("name") and form.has_key("age")):

print "<H1>Name & Age not Entered</H1>"

print "Fill the Name & Age accurately."

return

print "<p>name:", form["name"].value

print "<p>Age:", form["age"].value

python 2013-12-30 10:22:44

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