Python Interview Questions and Answers

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Python Interview Questions and Answers: Here are the best python questions and answers to crack your interview in first attempt and achieve you dream job. Please go through the article.

What are the key features of Python?

  • Python is an interpreted language. That means that, unlike languages like C and its variants, Python does not need to be compiled before it is run. Other interpreted languages include PHP and Ruby.
  • Python is dynamically typed, this means that you don’t need 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 in that it allows the definition of classes along with composition and inheritance. Python 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
  • Writing Python code is quick but running it is often slower than compiled languages. Fortunately,Python allows the inclusion of C-based extensions so bottlenecks can be optimized away and often are. The numpy package is a good example of this, it’s really quite quick because a lot of the number-crunching it does isn’t actually done by Python
  • 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.

How is memory managed in Python?

Memory is managed in Python in the following ways:

  1. Memory management in python is managed by Python private heap space. All Python objects and data structures are located in a private heap. The programmer does not have access to this private heap. The python interpreter takes care of this instead.
  2. The 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.
  3. 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.
Python interview Questions

What is an Interpreted language?

An Interpreted language executes its statements line by line. Languages such as Python, Javascript, R, PHP and Ruby are prime examples of Interpreted languages. Programs written in an interpreted language runs directly from the source code, with no intermediary compilation step.

Python Interview Questions and Answers

What is PEP 8 and why is it important?

PEP stands for Python Enhancement Proposal. A PEP is an official design document providing information to the Python Community, or describing a new feature for Python or its processes. PEP 8 is especially important since it documents the style guidelines for Python Code. Apparently contributing in the Python open-source community requires you to follow these style guidelines sincerely and strictly.

Which are the file related libraries/modules in Python?

The Python provides libraries/modules that enable you to manipulate text files and binary files on the file system. It helps to create files, update their contents, copy, and delete files. The libraries are os, os.path, and shutil.

Here, os and os.path – modules include a function for accessing the filesystem

while shutil – module enables you to copy and delete the files.

What are the different file processing modes supported by Python?

Python provides three modes to open files. The read-only, write-only, read-write and append mode. ‘r’ is used to open a file in read-only mode, ‘w’ is used to open a file in write-only mode, ‘rw’ is used to open in reading and write mode, ‘a’ is used to open a file in append mode. If the mode is not specified, by default file opens in read-only mode.

  • Read-only mode : Open a file for reading. It is the default mode.
  • Write-only mode: Open a file for writing. If the file contains data, data would be lost. Other a new file is created.
  • Read-Write mode: Open a file for reading, write mode. It means updating mode.
  • Append mode: Open for writing, append to the end of the file, if the file exists.

How to combine dataframes in pandas?

Two different data frames can be stacked either horizontally or vertically by the concat(), append() and join() functions in pandas.

Concat works best when the data frames have the same columns and can be used for concatenation of data having similar fields and is basically vertical stacking of dataframes into a single dataframe.

Append() is used for horizontal stacking of dataframes. If two tables(dataframes) are to be merged together then this is the best concatenation function.

Join is used when we need to extract data from different data frames which have one or more common columns. The stacking is horizontal in this case.

What are the positive and negative indices?

In the positive indices are applied the search beings from left to the right. In the case of the negative indices, the search begins from right to left. For example, in the array list of size n the positive index, the first index is 0, then comes 1 and until the last index is n-1. However, in the negative index, the first index is -n, then -(n-1) until the last index will be -1.

What can be the length of the identifier in Python Interview Questions and Answers?

The length of the identifier in Python can be of any length. The longest identifier will violate from PEP – 8 and PEP – 20.

Define Pass statement in Python?

A Pass statement in Python is used when we cannot decide what to do in our code, but we must type something for making syntactically correct.

What are the limitations of Python?

There are certain limitations of Python, which include the following:

  1. It has design restrictions.
  2. It is slower when compared with C and C++ or Java.
  3. It is inefficient in mobile computing.
  4. It consists of an underdeveloped database access layer.

Do runtime errors exist in Python? Give an example?

Yes, runtime errors exist in Python. For example, if you are duck typing and things look like a duck, then it is considered as a duck even if that is just a flag or stamp or any other thing. The code, in this case, would be A Run-time error. For example, Print “Hackr io”, then the runtime error would be the missing parenthesis that is required by print ( ).

Explain the use of “help()” and “dir()” functions?

In Python, the help() function is used for showing the documentation of modules, classes, functions, keywords, and so on. If the help() function receives no parameter, it launches an interactive help utility on the console.

The dir() function is used to return a valid list of attributes and methods of the object it is called upon. Since the function aims to produce the most relevant data (instead of showing the complete information), it behaves differently with different objects:

  • For modules/library objects, the dir() function returns a list of all attributes contained in that module.
  • For class objects, the dir() function returns a list of all valid attributes and base attributes.
  • When no parameters are passed to it, the dir() function returns a list of attributes in the current scope.

What are python modules? Name some commonly used built-in modules in Python?

Python modules are files containing Python code that can be either function classes or variables. These modules are Python files having a .py extension. Modules can include a set of functions, classes, or variables that are both defined and implemented. You can import and initialize a module using the import statement, learning python tutorial will let us know more about python modules.

Here are some of the commonly used built-in modules in Python:

  • os
  • sys
  • math
  • random
  • data time
  • JSON

Explain “self” in Python?

In Python, “self” is a keyword used to define an instance or object of a class. Unlike in Java, where the self is optimal, in Python, it is primarily used as the first parameter. Self helps to distinguish between the methods and attributes of a class from its local variables.

The self variable in the __init__ method refers to the newly created object or instance, while in other methods, it pertains to the object or instance whose method was called.

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