Python Interview Questions and Answers

• Python is a high-level and object-oriented programming language with unified semantics designed primarily for developing apps and web.

• It is the core language in the field of Rapid Application Development (RAD) as it offers options such as dynamic binding and dynamic typing.

Python is an interpreted language. It does not need to be compiled before it is run. Other interpreted languages include PHP and Ruby.

Python is dynamically typed and you don’t have to state the types of variables when you declare them or anything like that. You can do things like x=111 and then x=”I’m a string” without error

Python is well suited to object orientated programming as it allows the definition of classes along with composition and inheritance. It does not have access specifiers (like C++’s public, private).

In Python, functions are first-class objects. This means that they can be assigned to variables, returned from other functions and passed into functions. Classes are also first class objects

You can write python programs quickly but it takes time to run the program when compared to other languages. It allows the inclusion of C based extensions so bottlenecks can be optimised away and often are. The numpy package is a good example as it’s really quick.

Python finds use in many spheres – web applications, automation, scientific modeling, big data applications and many more. It’s also often used as “glue” code to get other languages and components to play nice.

Benefits of Python includes:

• Speed and Productivity: Utilizing the productivity and speed of Python will enhance the process control capabilities and possesses strong integration.

• Extensive Support for Libraries: Python provides a large standard library that includes areas such as operating system interfaces, web service tools, internet protocols, and string protocols. Most of the programming tasks are already been scripted in the standard library which reduces effort and time.

• User-friendly Data Structures: Python has an in-built dictionary of data structures that are used to build fast user-friendly data structures.

• Existence of Third Party Modules: The presence of third party modules in the Python Package Index (PyPI) will make Python capable to interact with other platforms and languages.

• Easy Learning: Python provides excellent readability and simple syntaxes to make it easy for beginners to learn.

Python is capable of scripting, but in general sense, it is considered as a general-purpose programming language. To know more about Scripting, you can refer to the Python Scripting Tutorial.

An interpreted language is any programming language which is not in machine level code before runtime. Therefore, Python is an interpreted language.

The applications of Python are as follows:

• GUI based desktop applications

• Image processing applications

• Business and Enterprise applications

• Prototyping

• Web and web framework applications

• Python is best suited for web server-side application development due to its vast set of features for creating business logic, database interactions, web server hosting etc.

• However, Python can be used as a web client-side application which needs some conversions for a browser to interpret the client side logic.

• Also, note that Python can be used to create desktop applications which can run as a standalone application such as utilities for test automation.

• PEP stands for Python Enhancement Proposal. It is a set of rules that specify how to format Python code for maximum readability.

• Python Private Heap Space is the key for Memory Management in Python. All Python objects and data structures are located in a private heap. The programmer does not have access to this private heap but the python interpreter plays a vital role in managing it.

• Allocation of heap space for Python objects is done by Python’s memory manager. The core API gives access to some tools for the programmer to code.

• Python also has an inbuilt garbage collector, which recycles all the unused memory and so that it can be made available to the heap space.

A namespace is a naming system that ensures that names are unique in order to avoid naming conflicts.

It is an environment variable which is used when a module is imported.

Whenever a module is imported, PYTHONPATH is also looked up to check for the presence of the imported modules in various directories. The interpreter uses it to determine which module to load.

Global Variables:

Variables declared outside a function or in global space are called global variables. These variables can be accessed by any function in the program.

Local Variables:

Any variable declared inside a function is known as a local variable. This variable is present in the local space and not in the global space.

List: Collection of items of different data types which can be changed at run time.

Tuple: Collection of items of different data types which cannot be changed. It only has read-only access to the collection. This can be used when you want to secure your data collection set and does not need any modification.

• Set: Collection of items of a similar data type.

• Dictionary: Collection of items with key-value pairs.

Generally, List and Dictionary are extensively used by programmers as both of them provide flexibility in data collection.

• In Python, memory management is done using private heap space. The private heap is the storage area for all the data structures and objects. The interpreter has access to the private heap and the programmer cannot access this private heap.

• The storage allocation for the data structures and objects in Python is done by the memory manager. The access for some tools is provided by core API for programmers to code.

• The built-in garbage collector in Python is used to recycle all the unused memory so that it can be available for heap storage area.

Yes. Python is a case sensitive language.

The built-in types in Python listed below:

• Integer

• Complex numbers

• Floating-point numbers

• Strings

• Built-in functions

Yes. It does allow to code is a structured as well as Object-oriented style. It offers excellent flexibility to design and implement your application code depending on the requirements of your application.

• PIP is an acronym for Python Installer Package which provides a seamless interface to install various Python modules.

• It is a command line tool which can search for packages over the internet and install them without any user interaction.

Indentation is necessary for Python. It specifies a block of code. All code within loops, classes, functions, etc is specified within an indented block. It is usually done using four space characters. If your code is not indented necessarily, it will not execute accurately and will throw errors as well.

A function is a block of code which is executed only when it is called. To define a Python function, the def keyword is used.

• For loop is generally used to iterate through the elements of various collection types such as List, Tuple, Set, and Dictionary.

• While loop is the actual looping feature that is used in any other programming language. This is how Python differs in handling loops from the other programming languages.

• In Python, there is no need to define a variable’s data type explicitly.

• Based on the value assigned to a variable, Python stores the appropriate data type. In case of numbers such as Integer, Float, etc, the length of data is unlimited.

Python does not support Arrays. However, you can use List collection type which can store an unlimited number of elements.

• Python has built-in support to handle JSON objects.

• You just have to import the JSON module and use the functions such as loads and dumps to convert from JSON string to JSON object and vice versa. It is a straightforward way to handle and exchange JSON based data from the server-side.

Decorator is the most useful tool in Python as it allows programmers to alter the changes in the behavior of class or function.

MySQL (Structured) and MongoDB (Unstructured) are the prominent databases that are supported natively in Python. Import the module and start using the functions to interact with the database.

It is the first function that gets executed when an object of a class is instantiated. This is equivalent to the constructor concept in C++.

We can detect bugs in python source code using a static analysis tool named PyChecker. Moreover, there is another tool called PyLint that checks whether the Python modules meet their coding standards or not.

.py files are Python source files. .pyc files are the compiled bytecode files that are generated by the Python Compiler.

By using python or pythonx.y, we can invoke Python interpreter. where x.y is the version of the Python interpreter.

String in Python is formed using a sequence of characters. Value once assigned to a string cannot be modified because they are immutable objects. String literals in Python can be declared using double quotes or single quotes.

Eg: print(“Hello”)

A namespace in Python can be defined as a system that is designed to provide a unique name for every object in python. Types of namespaces listed below:

• Local namespace

• Global namespace

• Built-in namespace

• Parameter ‘self’ is used to refer to the object properties of a class.

• ‘self’ parameter is supposed to be prefixed to the class object properties and it can have any name.

• Lambda is similar to the inline function in C programming. It returns a function object. It contains only one expression and can accept any number of arguments.

• In case of a normal function, you can define a function name, pass the parameter and mandatorily have a return statement. The Lambda function can be typically used for simple operations without the use of function names. It can also be used in the place of a variable.

• There are 3 main keywords i.e. try, except and finally which are used to catch exceptions and handle the recovering mechanism accordingly. Try is the block of a code which is monitored for errors. Except block gets executed when an error occurs.

• The benefit of the final block is to execute the code after trying for error. This block gets executed irrespective of whether an error occurred or not. Finally block is used to do the required cleanup activities of objects/variables.

For the most part, xrange and range are the exact same in terms of functionality. They both provide a way to generate a list of integers for you to use. The only difference is that range returns a Python list object and x range returns an xrange object.

This means that xrange doesn’t actually generate a static list at run-time like range does. It creates the values as you need them with a special technique called yielding. This technique is used with a type of object known as generators. That means that if you have a really gigantic range you’d like to generate a list for, say one billion, xrange is the function to use.

This is especially true if you have a memory sensitive system such as a cell phone that you are working with, as range will use as much memory as it can to create your array of integers, which can result in a Memory Error and crash your program. It’s a memory hungry beast.

Comments in Python start with a # character. However, alternatively at times, commenting is done using docstrings(strings enclosed within triple quotes).

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.

Functions that return an iterable set of items are called generators.

In Python, the capitalize() method capitalizes the first letter of a string. If the string already consists of a capital letter at the beginning, then, it returns the original string.

To convert a string to lowercase, lower() function can be used.

Functions return values using the return statement.

Slicing is a procedure used to select a particular range of items from sequence types such as Strings, lists, and so on.

The built-in modules in Python include

• Sys module

• OS module

• Random module

• Collection module

• JSON

• Math module

Garbage collection is an in-built feature in Python which takes care of allocating and de-allocating memory. This is very similar to the feature in Java.

Hence, there are very fewer chances of memory leaks in your application code.

Yes. As long as you have the Python environment on your target platform (Linux, Windows, Mac), you can run the same code.

Assert statement is used to evaluate the expression attached. If the expression is false, then python throws AssertionError Exception.

Match checks for the match at the beginning of the string whereas search checks for the match anywhere in the string