Top 100 Python Interview Questions and Answers

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Python is a high-level, interpreted, general-purpose programming language. Being a general-purpose language, it can be used to build almost any type of application with the right tools/libraries. Additionally, python supports objects, modules, threads, exception-handling, and automatic memory management which help in modelling real-world problems and building applications to solve these problems.

Benefits of using Python:

1. Python is a general-purpose programming language that has a simple, easy-to-learn syntax that emphasizes readability and therefore reduces the cost of program maintenance. Moreover, the language is capable of scripting, is completely open-source, and supports third-party packages encouraging modularity and code reuse.
2. Its high-level data structures, combined with dynamic typing and dynamic binding, attract a huge community of developers for Rapid Application Development and deployment.

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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.

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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.

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Lists and Tuples are both sequence data types that can store a collection of objects in Python. The objects stored in both sequences can have different data types.

Following are the key differences between List and Tuples:

1. Lists are mutable i.e they can be edited. Whereas, Tuples are immutable means tuples are lists which can’t be edited.
2. Lists are slower than tuples. In contrast, Tuples are faster than list.
3. Lists are represented with square brackets. While, tuples are represented with parantheses.

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The pass keyword represents a null operation in Python. It is generally used for the purpose of filling up empty blocks of code which may execute during runtime but has yet to be written. Without the pass statement in the following code, we may run into some errors during code execution.

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1. Global variables are public variables that are defined in the global scope. To use the variable in the global scope inside a function, we use the global keyword.
2. Protected attributes are attributes defined with an underscore prefixed to their identifier. They can still be accessed and modified from outside the class they are defined in but a responsible developer should refrain from doing so.
3. Private attributes are attributes with double underscore prefixed to their. They cannot be accessed or modified from the outside directly and will result in an AttributeError if such an attempt is made.

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Self is used to represent the instance of the class. With this keyword, you can access the attributes and methods of the class in python. It binds the attributes with the given arguments. self is used in different places and often thought to be a keyword.

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Break: The break statement terminates the loop immediately and the control flows to the statement after the body of the loop.

Continue: The continue statement terminates the current iteration of the statement, skips the rest of the code in the current iteration and the control flows to the next iteration of the loop.

Pass: As explained above, the pass keyword in Python is generally used to fill up empty blocks and is similar to an empty statement represented by a semi-colon in languages such as Java, C++, Javascript, etc.

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Following are the key differences between Python Arrays and Lists:

1. Arrays in python can only contain elements of same data types i.e., data type of array should be homogeneous. It is a thin wrapper around C language arrays and consumes far less memory than lists.
2. Lists in python can contain elements of different data types i.e., data type of lists can be heterogeneous. It has the disadvantage of consuming large memory

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Lambda is an anonymous function in Python, that can accept any number of arguments, but can only have a single expression. It is generally used in situations requiring an anonymous function for a short time period. Lambda functions can be used in either of the two ways:

1. Assigning lambda functions to a variable,
2. Wrapping lambda functions inside another function.

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Pickling: Pickling is the name of the serialization process in Python. Any object in Python can be serialized into a byte stream and dumped as a file in the memory. The process of pickling is compact but pickle objects can be compressed further. Moreover, pickle keeps track of the objects it has serialized and the serialization is portable across versions.

Unpickling: Unpickling is the complete inverse of pickling. It deserializes the byte stream to recreate the objects stored in the file and loads the object to memory.

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Generators are functions that return an iterable collection of items, one at a time, in a set manner. Generators, in general, are used to create iterators with a different approach.

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PYTHONPATH is an environment variable which you can set to add additional directories where Python will look for modules and packages. This is especially useful in maintaining Python libraries that you do not wish to install in the global default location.

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Pass by value: Copy of the actual object is passed. Changing the value of the copy of the object will not change the value of the original object.

Pass by reference: Reference to the actual object is passed. Changing the value of the new object will change the value of the original object.

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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.

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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.

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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.

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The built-in datatypes in Python is called dictionary. It defines one-to-one relationship between keys and values. Dictionaries contain pair of keys and their corresponding values. Dictionaries are indexed by keys.

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Array elements can be removed using pop() or remove() method. The difference between these two functions is that the former returns the deleted value whereas the latter does not.

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Multiple inheritance means that a class can be derived from more than one parent classes. Python does support multiple inheritance, unlike Java.