Python Interview Questions

Python is a high-level, interpreted, interactive and object-oriented scripting language. Python is designed to be highly readable. It uses English keywords frequently where as other languages use punctuation, and it has fewer syntactical constructions than other languages.

Following are some of the salient features of python −

• 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.

PEP 8 is a coding convention, a set of recommendation, about how to write your Python code more readable

Python language is an interpreted language. Python program runs directly from the source code. It converts the source code that is written by the programmer into an intermediate language, which is again translated into machine language that has to be executed.

PyChecker is a static analysis tool that detects the bugs in Python source code and warns about the style and complexity of the bug. Pylint is another tool that verifies whether the module meets the coding standard.

The difference between list and tuple is that list is mutable while tuple is not. Tuple can be hashed, for example., as a key for dictionaries.

Pickle module accepts any Python object and converts it into a string representation and dumps it into a file by using dump function. This process is called pickling. While the process of retrieving original Python objects from the stored string representation is called unpickling.

A Python decorator is a specific change that we make in Python syntax to alter functions easily.

They are syntax constructions to ease the creation of a Dictionary or List based on existing iterable.

Everything in Python is an object, and all variables hold references to the objects. The reference values are according to the functions. Therefore, you cannot change the value of the references. However, you can change the objects if it is mutable.

In Python, every name introduced has a place where it lives and can be hooked for. This is known as a namespace. It is like a box where a variable name is mapped to the object placed. Whenever the variable is searched out, this box will be searched to get the corresponding object.

In Python, iterators are used to iterate a group of elements, containers like a list.

A unit testing framework in Python is known as unittest. It supports sharing of setups, automation testing, shutdown code for tests, aggregation of tests into collections, etc.

It is a single expression anonymous function often used as inline function.

Pass means no-operation Python statement, or in other words, it is a place holder in a compound statement, where there should be a blank left, and nothing has to be written there.

Dict = {'Tim': 18,'Charlie':12,'Tiffany':22,'Robert':25}    
print("Students Name: %s" % list(Dict.items()))

Here is the list of dictionary methods:

• copy()
• update()
• items()
• sort()
• len()
• cmp()
• Str()

There are situations where sometimes people wish to have more thorough and fine access control over how much is to be read over in each iteration. To get better control in these cases it’s always the best idea to use iter and yield.

Python path is an environmental variable that is used in the case of the importing of a module. A module is introduced; the python path is used to check out the presence of the imported in all directories. With an interpreter, it is possible to decide which module is needed to load.

Global Variables: When variables are considered either outside a function or in global space, it is known as global variables. The fact, it is possible to access these variables from any function in the program.

Local Variables: When variables are considered inside a function, it is known as local variables. The fact, this variable is presented in the local space rather than in the global space.

To share global variables across modules within a single program, create a special module. Import the config module in all modules of your application. The module will be available as a global variable across modules.

To make a Python Script executable on Unix, you need to do two things,

Script file’s mode must be executable, and the first line must begin with # ( #!/usr/local/bin/python)

By using a command 

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

A Python documentation string is known as docstring, it is a way of documenting Python functions, modules, and classes.

The way of implementing iterators are known as generators. It is a normal function except that it yields expression in the function.

A mechanism to select a range of items from sequence types like list, tuple, strings etc., is known as slicing.

In order to convert a number into a string, use the inbuilt function str(). If you want a octal or hexadecimal representation, use the inbuilt function oct() or hex().

You can access a module written in Python from C by following method,

Module = PyImport_ImportModule("<modulename>");

It is a Floor Divisionoperator, which is used for dividing two operands with the result as a quotient showing only digits before the decimal point. For instance, 10//5 = 2 and 10.0//5.0 = 2.0.

The use of the split function in Python is that it breaks a string into shorter strings using the defined separator. It gives a list of all words present in the string.

The common way for the flask script to work is:

• Either it should be the import path for your application
• Or the path to a Python file

A session basically allows you to remember information from one request to another. In a flask, it uses a signed cookie so the user can look at the session contents and modify. The user can modify the session if only it has the secret key Flask.secret_key.

The data in the failed server won’t get removed, but there is a provision for auto-failure, which you can configure for multiple nodes. Fail-over can be triggered during any kind of socket or Memcached server level errors and not during normal client errors like adding an existing key, etc.

 Dogpile effect is referred to the event when cache expires, and websites are hit by the multiple requests made by the client at the same time. This effect can be prevented by using a semaphore lock. In this system, when the value expires, the first process acquires the lock and starts generating a new value.

The common examples of exceptions in Python are:

• Division by Zero
• Accessing a file that does not exist.
• Addition of two incompatible types
• Trying to access a nonexistent index of a sequence
• Removing the table from the disconnected database server.
• ATM withdrawal of more than the available amount

Code to print the star(*) pattern without newline and space:

for i in range(0, 20):
    print('*', end="")

It was developed in 1991.

You can run a Python code from the run option in the menu in an interpreter. A Python code can also run in command prompt code. It will run the program after entering the correct path of the file.

Python supports the below-mentioned built-in data types:

Immutable data types:

• Number
• String
• Tupl

Mutable data types:

• List
• Dictionary
• set

A Python package refers to the collection of different sub-packages and modules based on the similarities of the function.

Indentation in Python is compulsory and is part of its syntax.

All programming languages have some way of defining the scope and extent of the block of codes. In Python, it is indentation. Indentation provides better readability to the code, which is probably why Python has made it compulsory.

To add a multiple lines comment in python, all the line should be prefixed by #.

Generally, Python is an all purpose Programming Language ,in addition to that Python is also Capable to perform scripting.

Python does follow an object-oriented programming paradigm and has all the basic OOPs concepts such as inheritance, polymorphism, and more, with the exception of access specifiers. Python doesn’t support strong encapsulation (adding a private keyword before data members). Although, it has a convention that can be used for data hiding, i.e., prefixing a data member with two underscores.

• What does *args and **kwargs mean?*args: It is used to pass multiple arguments in a function.
• **kwargs: It is used to pass multiple keyworded arguments in a function in python

We can read a random line in a file using the random module.

For example:

import random
def read_random(fname):
lines = open(fname).read().splitlines()
return random.choice(lines)
print(read_random (‘hello.txt’))

The function list.reverse() reverses the objects of a list.

lower() function is used to convert a string to lowercase.

For Example:

demo_string='ROSES'
print(demo_string.lower())

Polymorphism is the ability of the code to take multiple forms. Let’s say, if the parent class has a method named XYZ then the child class can also have a method with the same name XYZ having its own variables and parameters.

encapsulation in Python refers to the process of wrapping up the variables and different functions into a single entity or capsule.Python class is the best example of encapsulation in python.