Python Fundamentals

Python Programming Interview Questions & Answers

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1) What is Python? What are the benefits of using Python? 

Python is a programming language with objects, modules, threads, exceptions and automatic memory management. The benefits of pythons are that it is simple and easy, portable, extensible, build-in data structure and it is an open source.
 

2) Name some of the features of Python. 

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. 

3) What is PEP 8? 

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

 
4) How Python is interpreted? 

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.
 

5) What is the purpose of PYTHONPATH environment variable? 

PYTHONPATH - It has a role similar to PATH. This variable tells the Python interpreter where to locate the module files imported into a program. It should include the Python source library directory and the directories containing Python source code. PYTHONPATH is sometimes preset by the Python installer.
 

6) What is the purpose of PYTHONSTARTUP environment variable?

PYTHONSTARTUP - It contains the path of an initialization file containing Python source code. It is executed every time you start the interpreter. It is named as .pythonrc.py in Unix and it contains commands that load utilities or modify PYTHONPATH.
 

7) What is the purpose of PYTHONCASEOK environment variable? 

PYTHONCASEOK − It is used in Windows to instruct Python to find the first case-insensitive match in an import statement. Set this variable to any value to activate it.

 
8) What is pickling and unpickling? 

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.
 

9) What are the tools that help to find bugs or perform static analysis? 

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.
 

10) What are Python decorators? 

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

 
11) Is python a case sensitive language? 

Yes! Python is a case sensitive programming language.
 

12) What is the difference between list and tuple? 

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

13) What are the supported data types in Python? 

Python has five standard data types −

• Numbers
• String
• List
• Tuple
• Dictionary

 
14) How are arguments passed by value or by reference? 

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

15) What is Dict and List comprehensions are? 

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

 
16) What is namespace in Python? 

In Python, every name introduced has a place where it lives and can be hooked for. This is known as 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 corresponding object.
 

17) What is lambda in Python? 

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

18) Why lambda forms in python does not have statements? 

A lambda form in python does not have statements as it is used to make new function object and then return them at runtime.

 
19) How long can an identifier be in Python?

According to the official Python documentation, an identifier can be of any length. However, PEP 8 suggests that you should limit all lines to a maximum of 79 characters. Also, PEP 20 says ‘readability counts’. So, a very long identifier will violate PEP-8 and PEP-20.
 

20) How would you convert a string into lowercase? 

We use the lower() method for this.

 
21) What is the pass statement in Python? 

There may be times in our code when we haven’t decided what to do yet, but we must type something for it to be syntactically correct. In such a case, we use the pass statement.
 

22) What are Python's dictionaries? 

Python's dictionaries are kind of hash table type. They work like associative arrays or hashes found in Perl and consist of key-value pairs. A dictionary key can be almost any Python type, but are usually numbers or strings. Values, on the other hand, can be any arbitrary Python object.

 
23) How will you create a dictionary using tuples in python? 

dict(d) − Creates a dictionary. d must be a sequence of (key,value) tuples.

 
24) How will you convert a string to a frozen set in python? 

frozenset(s) − Converts s to a frozen set.
 

25) How will you convert an integer to a character in python? 

chr(x) − Converts an integer to a character.

 
26) How will you convert an integer to an unicode character in python? 

unichr(x) − Converts an integer to a Unicode character.
 

27) How will you convert a single character to its integer value in python? 

ord(x) − Converts a single character to its integer value.
 

28) What is pass in Python? 

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

 
29) In Python what are iterators? 

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

 
30) What is unittest in Python? 

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.

 
31) What are generators in Python? 

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

 
32) What is docstring in Python? 

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

33)  How would you define a block in Python? 

For any kind of statements, we possibly need to define a block of code under them. However, Python does not support curly braces. This means we must end such statements with colons and then indent the blocks under those with the same amount.
 

34) Why do we need break and continue in Python?

Both break and continue are statements that control flow in Python loops. break stops the current loop from executing further and transfers the control to the next block. continue jumps to the next iteration of the loop without exhausting it.

 
35) What is the purpose of // operator?

 // Floor Division − The division of operands where the result is the quotient in which the digits after the decimal point are removed.
 

36)  What is the purpose of "is" operator?

 is − Evaluates to true if the variables on either side of the operator point to the same object and false otherwise. x is y, here is results in 1 if id(x) equals id(y).
 

37) What is the purpose of "not in" operator? 

not in − Evaluates to true if it does not finds a variable in the specified sequence and false otherwise. x not in y, here not in results in a 1 if x is not a member of sequence y.

 
38) What is negative index in Python? 

Python sequences can be index in positive and negative numbers. For positive index, 0 is the first index, 1 is the second index and so forth. For negative index, (-1) is the last index and (-2) is the second last index and so forth.
 

39) What is the difference between Xrange and range? 

Xrange returns the xrange object while range returns the list, and uses the same memory and no matter what the range size is.
 

40) What is module and package in Python? 

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

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