Python Interview Questions and Answers



Python is an interpreted, interactive, object-oriented programming language. It incorporates modules, exceptions, dynamic typing, very high level dynamic data types, and classes. Python combines remarkable power with very clear syntax. It has interfaces to many system calls and libraries, as well as to various window systems, and is extensible in C or C++. It is also usable as an extension language for applications that need a programmable interface. Finally, Python is portable: it runs on many Unix variants, on the Mac, and on PCs under MS-DOS, Windows, Windows NT, and OS/2.
Yes., PyChecker is a static analysis tool that finds bugs in Python source code and warns about code complexity and style. Pylint is another tool that checks if a module satisfies a coding standard, and also makes it possible to write plug-ins to add a custom feature.
For an instance x of a user-defined class, dir(x) returns an alphabetized list of the names containing the instance attributes and methods and attributes defined by its class.
A class is the particular object type created by executing a class statement. Class objects are used as templates to create instance objects, which embody both the data (attributes) and code (methods) specific to a datatype. A class can be based on one or more other classes, called its base class(es). It then inherits the attributes and methods of its base classes. This allows an object model to be successively refined by inheritance. You might have a generic Mailbox class that provides basic accessor methods for a mailbox, and subclasses such as MboxMailbox, MaildirMailbox, OutlookMailbox that handle various specific mailbox formats.
A method is a function on some object x that you normally call as x.name(arguments...). Methods are defined as functions inside the class definition: class C: def meth (self, arg): return arg*2 + self.attribute
Self is merely a conventional name for the first argument of a method. A method defined as meth(self, a, b, c) should be called as x.meth(a, b, c) for some instance x of the class in which the definition occurs; the called method will think it is called as meth(x, a, b, c).

Use os.remove(filename) or os.unlink(filename);

There are (at least) three kinds of modules in Python:
1. modules written in Python (.py);
2. modules written in C and dynamically loaded (.dll, .pyd, .so, .sl, etc);
3. modules written in C and linked with the interpreter; to get a list of these, type:
import sys
print sys.builtin_module_names

The shutil module contains a copyfile() function.

 

Use the popen2 module. For example:
import popen2
fromchild, tochild = popen2.popen2("command")
tochild.write("input ")
tochild.flush()
output = fromchild.readline()

The select module is commonly used to help with asynchronous I/O on sockets.

Yes.
Python 2.3 includes the bsddb package which provides an interface to the BerkeleyDB library. Interfaces to disk-based hashes such as DBM and GDBM are also included with standard Python.

The standard module random implements a random number generator. Usage is simple:
import random
random.random()
This returns a random floating point number in the range [0, 1).

Yes, you can create built-in modules containing functions, variables, exceptions and even new types in C.

 

The highest-level function to do this is PyRun_SimpleString() which takes a single string argument to be executed in the context of the module __main__ and returns 0 for success and -1 when an exception occurred (including SyntaxError).

Depending on your requirements, there are many approaches. To do this manually, begin by reading the "Extending and Embedding" document. Realize that for the Python run-time system, there isn't a whole lot of difference between C and C++ -- so the strategy of building a new Python type around a C structure (pointer) type will also work for C++ objects.

Python can be very well used for web programming and it also has some special features which make you to write the programming language very easily. Some of the features which it supports are Web frame works, Cgi scripts, Webservers, Content Management systems, Web services, Webclient programming, Webservices, etc. Many high end applications can be created with Python because of the flexibility it offers.

Python has an internal software mechanism which makes your programming easy. Program can run directly from the source code. Python translates the source code written by the programmer into intermediate language which is again translated it into the native language of computer. This makes it easy for a programmer to use python.

Python supports object oriented programming as well as procedure oriented programming. It has features which make you to use the program code for many functions other than Python. It has useful objects when it comes to data and functionality. It is very powerful in object and procedure oriented programming when compared to powerful languages like C or Java

 

Python library is very huge and has some extensive libraries. These libraries help you do various things involving CGI, documentation generation, web browsers, XML, HTML, cryptography, Tk, threading, web browsing, etc. Besides the standard libraries of python there are many other libraries such as Twisted, wx python, python imaging library, etc.

 

Strings are almost used everywhere in python. When you use single and double quotes for a statement in python it preserves the white spaces as such. You can use double quotes and single quotes in triple quotes. There are many other strings such as raw strings, Unicode strings, once you have created a string in Python you can never change it again.

 

A dictionary is a place where you will find and store information on address, contact details, etc. In python you need to associate keys with values. This key should be unique because it is useful for retrieving information. Also note that strings should be passed as keys in python. Notice that keys are to be separated by a colon and the pairs are separated themselves by commas. The whole statement is enclosed in curly brackets.

 

Tuples, lists and strings are some examples about sequence. Python supports two main operations which are indexing and slicing. Indexing operation allows you to fetch a particular item in the sequence and slicing operation allows you to retrieve an item from the list of sequence. Python starts from the beginning and if successive numbers are not specified it starts at the last. In python the start position is included but it stops before the end statement.

In python programmer can raise exceptions using the raise statement. When you are using exception statement you should also specify about error and exception object. This error should be related to the derived class of the Error. We can use this to specify about the length of the user name, password field, etc.

This lambda statement is used to create a new function which can be later used during the run time. Make_repeater is used to create a function during the run time and it is later called at run time. Lambda function takes expressions only in order to return them during the run time.

 

Python has a standard module known as Pickle which enables you to store a specific object at some destination and then you can call the object back at later stage. While you are retrieving the object this process is known as unpickling. By specifying the dump function you can store the data into a specific file and this is known as pickling.

 

A tuple is a list that is immutable. A list is mutable i.e. The members can be changed and altered but a tuple is immutable i.e. the members cannot be changed.
Other significant difference is of the syntax. A list is defined as
list1 = [1,2,5,8,5,3,]
list2 = ["Sachin", "Ramesh", "Tendulkar"]
A tuple is defined in the following way
tup1 = (1,4,2,4,6,7,8)
tup2 = ("Sachin","Ramesh", "Tendulkar")






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