Python Interview Questions and Answers

A high-level, interactive, and object-oriented scripting language, Python is a highly readable language that makes it ideal for beginner-level programmers. It uses English keywords and has fewer syntactical constructions as compared to other languages.

• Extensive Support Libraries
• Extensive Integration Features
• Improves Programmer's Productivity
• Platform Independent

Python 3.8.2

In total, there are 33 keywords in Python. It is important to know them all in order to know about their use so we can utilize them. In additon, while we are naming a variable, the name cannot be matched with the keywords. This is another reason to know all the keywords.

Pickling in Python basically refers to the method of serializing the objects within multiple binary streams. It is used to save the state of the objects and then reuse them at another time without losing instance-specific data.

Unpickling is simply the opposite of pickling

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Python is an interpreted language. It runs directly from the source code and converts the source code into an intermediate language. This intermediate language is translated into machine language and has to be executed.

Memory is managed by the private heap space. All objects and data structures are located in a private heap, and the programmer has no access to it. Only the interpreter has access. Python memory manager allocates heap space for objects. The programmer is given access to some tools for coding by the core API. The inbuilt garbage collector recycles the unused memory and frees up the memory to make it available for the heap space.

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For performing Static Analysis, PyChecker is a tool that detects the bugs in source code and warns the programmer about the style and complexity. Pylint is another tool that authenticates whether the module meets the coding standard.

Decorators are specific changes that we make in syntax to alter functions.

Everything in Python is like an object. All variables hold different references to the objects. The values of references are as per their functions. As a result, the programmer cannot change the value of the references. However, he can change the objects if they are mutable.

Dict and List are syntax constructions that ease the creation of a Dictionary or List based on iterables.

In Python, every name has a place where it lives and can be tied to. This is called a namespace. A namespace is like a box where a name is mapped with the object. Whenever the variable is searched, this box will also be searched in order to find the corresponding object.

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

Lambda is an anonymous expression function that is often used as an inline function. Its form does not have a statement as it is only used to make new functional objects and then return them at the runtime.

If you assign a new value to a variable anywhere within the function's body, it is assumed to be local. The variables that are referenced inside a function are known as global.

In order to share global variables across different modules within a single program, you need to create a special module. After that, just import the config module in all of the modules of your application. This will make the module available as a global variable across all the modules.

Pass means where there is a no-operation Python statement. It is just a placeholder in a compound statement where nothing needs can be written. The continue makes the loop to resume from the next iteration.

In Python, the negative index is used to index by starting from the last element in a list, tuple, or any other container class which supports indexing. Here, (-1) points to the previous index, -2 to the second last index and similarly.

The module is a way to structure a program. Each Python program is a module, which imports other modules such as objects and attributes. The entire folder of the Python program is a package of modules. A package can have both modules or subfolders.

A Flask is a micro web framework for Python based on the "Werkzeug, Jinja 2 and good intentions". Werkzeug and jingja are its dependencies. Because a Flask is part of the micro-framework, it has little or no dependencies on the external libraries. A Flask also makes the framework light while taking little dependency and gives fewer security bugs.

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A Flask is a microframework build for small applications with more straightforward requirements. Flask comes ready to use.

Pyramids are built for larger applications. They provide flexibility and allow the developer to use the right tools for their projects. The developer is free to choose the database, templating style, URL structure, and more. Pyramids is configurable.

Similar to Pyramids, Django can be used for larger applications. It includes an ORM.

A thread is a lightweight process. Multithreading allows the programmer to execute multiple threads in one go. The Global Interpreter Lock ensures that a single thread performs at a given time. A thread holds the GIL and does some work before passing it on to the next thread. This looks like parallel execution, but actually, it is just threading taking turns at the CPU.

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Python supported 5 data types.

• Numbers
• String
• Tuple
• Dictionary
• List

from random import shuffle

x = ['My', 'Singh', 'Hello', 'India']

shuffle(x)

print(x)

The output of the following code is as below.

['Singh', 'India', 'Hello', 'My']

In Python, an array of random integers can be generated through the function randint () NumPy. This function usually starts with three arguments; from the lower end, the upper-end range and the number of actual integer values to successfully generate the size of the array.

Python does not support the unary operators; rather, it supports augmented assignment operators.

The arithmetic operators it supports are as follows-

• Addition- '+'
• Subtraction- '-'
• Multiplication- '*'
• Division- '/:
• Modulo division- '%'
• Power of- '**'
• Floor div- '//'

PEP in Python stands for Python Enhancement Proposal. The PEP 8 is basically Python’s style guide. It helps in writing code to specific rules making it helpful for large codebases having multiple writers by bringing a uniform and predictive writing style.

Method resolution order or MRO refers to when one class inherits from multiple classes. The class that gets inherited is the parent class and the class that inherits is the child class. It also refers to the order where the base class is searched while executing the method.

This function returns to a printable presentation for the given object. It takes a single object & its syntax is repr(obj). The function repr computes all the formal string representation for the given object in Python.

Both lists and arrays in Python can store the data in the same way.
The difference is-

It refers to the method which adds a certain value to the class. It can’t be initiated by the user rather only occurs when an internal action takes charge. In python, the built-in classes define a number of magic methods.

The entity that changes the data types from one form to another is known as typecasting. In programming languages, it is used to make sure the variables are processed in the correct sequence by the function.

E.g., while converting an integer to string.

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The built-in method which decides the types of the variable at the program runtime is known as type() in Python. When a single argument is passed through it, then it returns given object type. When 3 arguments pass through this, then it returns a new object type.

In order to get the ASCII values in Python, you have to type a program. The function here will get the int value of char. This program must be in ord function() to return the value.

There are two categories of ‘types’ present in Python, which is mutable and immutable.

Mutable built-in types

• List
• Dictionary
• Set

Immutable built-in type

• String
• Number
• Tuple

In Python '//' operator is a floor Division operator. It is used to distinguish operands with their result as quotient representing the digits before the decimal point.

E.g. 10//5=2
10.5//5.0=2.0

Python iterators are used to traverse the elements or any collection for the specific implementation. In Python, they also regulate the iterator protocol and contain specific values.

• Select the URL you want to scrap
• Inspect the page
• Select data you want to extract
• Write the codes and run them

Once the data is extracted store the data in any required format

The way of using the operating system dependent functionalities is an OS module. Through this function, the interface is provided with the underlying operating system for which Python is running on.

DeQue module is a segment of the collection library that has a feature of addition and removal of the elements from their respective ends.

It is a Python library used to optimize, define, and execute the mathematical expressions including multidimensional arrays.

Here are some important features of Python:

• Being easy to learn, it is considered as the best language for beginner developers.
• It is an interpreted language.
• It is cross-platform in nature.
• Free and Open source
• It is based on an Object-Oriented Programming Language (OOPS)
• It has extensive in-built libraries

In Python, a self variable is used for binding the instance within the class to the instance inside the method. In this, to access the instance variables and methods, we have to explicitly declare it as the first method argument.

In Python, the use of the xrange() function is to generate a sequence of numbers that are similar to the range() function. But, the xrange() function is used only in Python 2. xx whereas the range() is used in Python 3.

In Python, an empty class can be created by using the “pass” command. This can be done only after the defining of the class object because at least one line of code is mandatory for creating a class. Here’s an example of how to create an empty class:

One of the many confusing questions in Python, yes, Python does support threading, but, due to the presence of GIL multi-threading is not supported. The GIL basically does not support the running of multiple CPU cores parallelly, hence, multithreading is not supported in Python.

The "init" is an example of a reserved method in python classes. It is actually known as a constructor in the object-oriented concepts and techniques. It is called when an object is created within a class, and then it allows the same class to initialize the attributes within.

Here's a program to check whether a number is prime or not.

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In Python, the term monkey patching refers to the dynamic/run-time changes taking place within a class or module. Here's an example:

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In Python, to display a null object, the None statement is used. Here's the syntax to check for if the object is null:

When a module is imported in Python, the following happens behind the scenes:
It starts with searching for mod.py in a list of directories which have been gathered from the following sources:

• The original directory from where the input script was actually being run or in the current list if the interpreter is being run interactively side by side.
• List of the directories within the PYTHONPATH environment variable, if it is actually set.
• A directory list from the installed directories would have been configured at the time of installation of Python itself.

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The range() is an in-built function in Python, which is used to repeat an action for a specific number of times.

Let us give you an example to demonstrate how the range() function works:

Here’s how to call a superclass method in python:

You should use a try-except keyword to capture the error and use the raise keyword to display the error message of your choice. Here's an example demonstrating the same:

try:
    a = int(input())
except:
    raise Exception('An error is being raised in the system')

The Slicing() object in Python allows users to access parts and sequences of data types such as strings, tuples, and lists. Slicing can also be used to modify or even delete items that have mutable sequences such as lists. Besides that, slices can also be integrated with third-party apps like NumPy arrays, data frames, and Panda series.

Syntax: slice(start, stop, step)

In Python, the dir() function is used to return all the properties and methods within a specified object, without actually having the values. The dir() function shall return all the features and methods present, including the in-built properties, which are set as default for all the objects within.

In Python, dictionaries are essential as they are incredibly flexible, and they allow any data which is given to be stored as a value. It could be anything such as primitive types like strings and decimals like floats to even more complex types like objects.

In Python, a shallow copy essentially means building a new collection of objects and then referencing it with the child objects found in the original group of the object.

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To create a named tuple in Python, follow these steps:

• Import the namedtuple class from the collections module.
• Now, the constructor shall take the name of the named tuple and a string containing the names of the field, separated by whitespace.
• The above action shall return a new namedtuple class for the specified fields.
• To use the new namedtuple, call the new class with all the values (in order) as parameters.

To send an email in Python, follow these steps along with the code: