20 Essential Python Interview Questions You Should Know

Python is the 4th most in-demand programming languages sought after by employers. Many IT companies hunt for good Python programmers and ready to shell out higher pays for the right candidate. So here are 20 essential Python interview questions to acquaint you with the skills and knowledge required to succeed in a job interview.

In this post, you’ll see that we’ve covered a wide range of Python programming areas by adding the most relevant questions. Our team which includes experienced Python developers have made a careful selection of the questions keeping our focus on the language, rather limiting to a particular topic. So that, you can get the full advantage.

Not only the job aspirants but also the recruiters can refer this post to know the right set of questions to evaluate a candidate. Let’s now step-in to explore the Python Q&A section.

20 Essential Python Interview Questions You Should Know.

Q-1: What is Python? What are the benefits of using Python? What do you understand of PEP 8?
Q-2: What is the output of the following Python code fragment? Justify your answer.
Q-3: What is the statement that can be used in Python if the program requires no action but requires it syntactically?
Q-4: What’s the process to get the home directory using ‘~’ in Python?
Q-5: What are the built-in types available in Python?
Q-6: How to find bugs or perform static analysis in a Python application?
Q-7: When is the Python decorator used?
Q-8: What is the key difference between a list and the tuple?
Q-9: How does Python handle the memory management?
Q-10: What are the principal differences between the lambda and def?
Q-11: Write a reg expression that confirms an email id using the python reg expression module <re>?
Q-12: What do you think is the output of the following code fragment? Is there any error in the code?
Q-13: Is there a switch or case statement in Python? If not then what is the reason for the same?
Q-14: What is a built-in function that Python uses to iterate over a number sequence?
Q-15: What are the optional statements that can be used inside a <try-except> block in Python?
Q-16: How does the ternary operator work in Python?
Q-17: What does the “self” keyword do?
Q-18: How to copy an object in Python?
Q-19: What is the purpose of doc strings in Python?
Q-20: Which Python function will you use to convert a number to a string?

Python Interview Questions and Answers.

Essential Python Interview Questions for Programmers

Essential Python Interview Questions.

Let’s begin answering the first ten intermediate-level interview questions.

 

Q-1: What is Python? What are the benefits of using Python? What do you understand of PEP 8?

Python is one of the most successful interpreted languages. When you write a Python script, it doesn’t need to get compiled before execution. Few other interpreted languages are PHP and Javascript.

Benefits of Python Programming.

  • Python is a dynamic-typed language, this means that you don’t need to mention the date type of variables during their declaration. It allows to set variables like var1=101 and var2 =” You are an engineer.” without any error.
  • Python supports object orientated programming as you can define classes along with the composition and inheritance. It doesn’t use access specifiers like public or private).
  • Functions in Python are like first-class objects. It suggests you can assign them to variables, return from other methods and pass as arguments.
  • Developing using Python is quick but running it is often slower than compiled languages. Luckily, Python enables to include the “C” language extensions so you can optimize your scripts.
  • Python has several usages like web-based applications, test automation, data modeling, big data analytics and much more. Alternatively, you can utilize it as “glue” layer to work with other languages.

PEP 8.

PEP 8 is the latest Python coding standard, a set of coding recommendations. It guides to deliver more readable Python code.

 

Q-2: What is the output of the following Python code fragment? Justify your answer.

The result of the above Python code snippet is:

You may erroneously expect list1 to be equal to [10] and list3 to be equal to [‘a’], thinking that the list argument will initialize to its default value of [] every time there is a call to the extendList.

However, the flow is like that a new list gets created once after the function is defined. And the same list is used whenever someone calls the extendList method without a list argument. It works like this because the calculation of expressions (in default arguments) occurs at the time of function definition, not during its invocation.

The list1 and list3 are hence operating on the same default list, whereas list2 is running on a separate list that it has created on its own (by passing an empty list as the value of the list parameter).

The definition of the extendList function can get changed in the following manner.

With this revised implementation, the output would be:

 

Q-3: What is the statement that can be used in Python if the program requires no action but requires it syntactically?

The pass statement is a null operation. Nothing happens when it executes. You should use “pass” keyword in lowercase. If you write “Pass” you’ll face an error like “NameError: name Pass is not defined.” Python statements are case sensitive.

 

Q-4: What’s the process to get the home directory using ‘~’ in Python?

You need to import the os module, and then just a single line would do the rest.

Output:

 

Q-5: What are the built-in types available in Python?

Here is the list of most commonly used built-in types that Python supports:

  • Immutable built-in types of Python
    • Numbers
    • Strings
    • Tuples
  • Mutable built-in types of Python
    • List
    • Dictionaries
    • Sets

 

Q-6: How to find bugs or perform static analysis in a Python application?

  • You can use PyChecker, which is a static analyzer. It identifies the bugs in Python project and also reveals the style and complexity related bugs.
  • Another tool is Pylint, which checks whether the Python module satisfies the coding standard.

 

Q-7: When is the Python decorator used?

Python decorator is a relative change that you do in Python syntax to adjust the functions quickly.

 

Q-8: What is the key difference between a list and the tuple?

List vs Tuple.

The major difference between a list and the tuple is that the list is mutable while tuple is not. A tuple is allowed to be hashed, for example, using it as a key for dictionaries.

 

Q-9: How does Python handle the memory management?

  • Python uses private heaps to maintain its memory. So the heap holds all the Python objects and the data structures. This area is only accessible to the Python interpreter; programmers can’t use it.
  • And it’s the Python memory manager that handles the Private heap. It does the required allocation of the heap for Python objects.
  • Python employs a built-in garbage collector, which salvages all the unused memory and offloads it to the heap space.

 

Let’s now answer the remaining ten advanced-level interview questions.

 

Q-10: What are the principal differences between the lambda and def?

lambda vs def.

  • def can hold multiple expressions while lambda is a uni-expression function.
  • def generates a function and designates a name so as to call it later. lambda forms a function and returns the function itself.
  • def can have a return statement. lambda can’t have return statements
  • lambda supports to get used inside a list and dictionary.

 

Q-11: Write a reg expression that confirms an email id using the python reg expression module <re>?

Python has a regular expression module <re>.

Check out the <re> expression that can check the email id for .com and .co.in subdomain.

 

Q-12: What do you think is the output of the following code fragment? Is there any error in the code?

The result of the above lines of code is []. There won’t be any error like an IndexError.

You should know that trying to fetch a member from the list using an index that exceeds the member count (for example, attempting to access list[10] as given in the question) would yield an IndexError. By the way, retrieving only a slice at an opening index that surpasses the no. of items in the list won’t result in an IndexError. It will just return an empty list.

 

Q-13: Is there a switch or case statement in Python? If not then what is the reason for the same?

No, Python does not have a Switch statement, but you can write a Switch function and then use it.

 

Q-14: What is a built-in function that Python uses to iterate over a number sequence?

range() generates a list of numbers, which is used to iterate over for loops.

The range() function accompanies two sets of parameters.

  • range(stop)
    • stop: It is the no. of integers to generate and starts from zero. eg. range(3) == [0, 1, 2].
  • range([start], stop[, step])
    • start: It is the starting no. of the sequence.
    • stop: It specifies the upper limit of the sequence.
    • step: It is the incrementing factor for generating the sequence.
  • Points to note:
    • Only integer arguments are allowed.
    • Parameters can be positive or negative.
    • The <range()> function in Python starts from the zeroth index.

 

Q-15: What are the optional statements that can be used inside a <try-except> block in Python?

There are two optional clauses you can use in the <try-except> block.

  • The <else> clause
    • It is useful if you want to run a piece of code when the try block doesn’t create any exception.
  • The <finally> clause
    • It is useful when you want to execute some steps which run, irrespective of whether there occurs an exception or not.

 

Q-16: How does the ternary operator work in Python?

The ternary operator is an alternative for the conditional statements. It combines of the true or false values with a statement that you need to test. The syntax would look like the one given below.

[onTrue] if [Condition] else [onFalse]

 

Q-17: What does the <self> keyword do?

The <self> keyword is a variable that holds the instance of an object. In almost, all the object-oriented languages, it is passed to the methods as hidden parameter.

 

Q-18: What are different methods to copy an object in Python?

There are two ways to copy objects in Python.

  • copy.copy() function
    • It makes a copy of the file from source to destination.
    • It’ll return a shallow copy of the parameter.
  • copy.deepcopy() function
    • It also produces the copy of an object from the source to destination.
    • It’ll return a deep copy of the parameter that you can pass to the function.

 

Q-19: What is the purpose of doc strings in Python?

In Python, documentation string is popularly known as doc strings. It sets a process of recording Python functions, modules, and classes.

 

Q-20: Which Python function will you use to convert a number to a string?

For converting a number into a string, you can use the built-in function <str()>.  If you want an octal or hexadecimal representation, use the inbuilt function <oct()> or <hex()>.

 

Summary – 20 Essential Python Interview Questions.

We always try to bring the fresh set of questions and attempt to provide reasonable answers. We hope the latest edition of Python interview questions would be as useful as the previous one was. If you want us to take upon a new subject, then please do let us know. We’ll certainly add it to our roadmap.

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