10 questions and answers to help you ace the Python interview

What to expect from interviewers, plus fundamental concepts you need to know

Oct 13, 2022

Hey Grokking Python readers, and happy Thursday!

In September, we dove deeply into careers and how you can become the Python developer you aspire to be. We devoted three editions to:

Today, we'll continue this theme and focus on an essential ingredient for landing your dream job: succeeding at interviews! Because of Python's popularity, many hiring managers and recruiters ask candidates about their Python knowledge during job interviews, even if the role is not Python-specific. If you want to be a Python developer, meanwhile, you can be sure you'll hear questions specifically about it!

Now, it can be challenging to prepare for an interview when you're unfamiliar with the types of questions that come up or how to answer them. So, in this edition, we'll start by covering the fundamental knowledge and concepts you need. We'll then run through 10 general Python questions you might encounter, along with brief answers covering essential points. (We won't be covering coding problems.)

Let's get to it!

Key areas of knowledge

During a technical interview for a Python developer position, you'll likely be asked a short series of technical questions to test your familiarity and comfort with the language, followed by some live coding exercises.

We'll focus on the first portion of the Python developer interview to help you get comfortable articulating abstract concepts and connecting them to your projects. You may be expected to explain and compare technical concepts, weigh the advantages and disadvantages of different approaches, or provide insight into your personal preferences as a developer.

Here are some key areas of Python that you'll need to understand for technical interviews:

Fundamentals like syntax, variables, data types, and control flow (if/else)
Data structures like lists, linked lists, stacks, queues, trees, tuples, sets, dictionaries, etc.
Implementing algorithms in Python for searching, sorting, graph traversal, and more.
- Algorithm design techniques such as brute-force, greedy, dynamic programming, divide-and-conquer, etc.
Object-oriented programming concepts like classes, objects, inheritance, polymorphism, encapsulation, and abstraction
Recursion and iteration for efficient problem solving
Exception handling for errors

Other topics may come up in your technical interview as well. You may end up discussing modules, packages, or libraries like NumPy and SciPy. Some advanced topics include concurrency, parallel processing, system design patterns, and Python tools used for profile or performance analysis.

Python interview questions

1. What are the main features of Python?

Ease of use: Python is very readable, even for beginners. It is often said that Python code looks like English, making programming much easier.
Open source: The Python programming language is freely available to everyone, so there are no licensing risks. You can use it to develop your applications without getting permission from anyone.
Cross-platform: Python supports many platforms, including Windows, Linux, and Mac OS X, and this high portability makes it suitable for use in a wide variety of different environments. It can also compile and run on a wide variety of different processor architectures.
Debugging support: Python comes with an integrated debugger that allows you to track the execution of your program, identify and resolve errors quickly, and troubleshoot issues as they arise. Many Python programmers also use third-party debugging tools like PyCharm, which provides a graphical user interface for interacting with your programs and making changes.
Extensible: Python code can be written into C or C++ and then compiled into those languages.
High-level: Python is very high-level compared to most programming languages, so you don't have to spend a lot of time learning a lot of technical jargon before you start using it. This makes it a great option for people just starting to program.
Object-oriented paradigm: Python supports the object-oriented programming paradigm, which means that you can develop a wide range of applications using objects to represent data and manipulate that data in the form of lists, dictionaries, tuples, and other data structures.
GUI programming support: Python modules like Tkinter enable you to create graphical user interfaces for your programs using the popular Tk graphical toolkit. These interfaces allow the user to interact with your application using mouse gestures and typing on the keyboard.
Multi-purpose language: Python is used for app development, machine/deep learning AI, data science, and more.

2. What are the benefits of using Python?

Simplicity: Python is easy to learn and use, and its simple syntax makes it easy to read and interpret. This means that it's much easier to write high-quality code in Python than in other languages.
Speed: Python is very lightweight compared to many other languages, which makes it much faster to execute on computers with limited resources. It's not as fast as some low-level languages like C or C++, but it's fast enough for most applications.
Dynamically typed: Python allows you to perform type inference when a variable is declared without specifying the data type, so there's no need to define the type of each variable explicitly.
Easy debugging: Python has several built-in functions that facilitate debugging your code, including the trace function, which displays information about the execution of a program and allows you to display variables at certain points in execution, and the debug module, which provides a debugger that you can use to display the values of variables at runtime and examine the state of your program at specific points in its execution.
Use by tech giants: Knowing Python will put you in the company of engineers at companies like Google, Meta, and more.

3. What are Python's built-in data types?

Assigning a value to a variable in Python assigns a data type at the same time. Eight data types are built into Python by default: numeric, text, boolean, sequence, mapping, set, binary, and none.

Numeric: int, float, complex
Text: str
Boolean: bool
Sequence: list, tuple, range
Mapping: dict
Set: set, frozenset
Binary: bytes, bytearray, memoryview
None: NoneType

You can find the type of any object by using the type() function.

# numeric types a = 123 b = 4.49 c = 64j # text types d = "Sphinx of black quartz, judge my vow." # booleans e = True f = False # sequence types g = ["red", "yellow", "blue"] h = ("Mario", "Luigi", "Alexander Hamilton") i = range(10) # mapping types j = {"Favorite food": "Coffee Jelly", "Power Level": 9001} # sets k = {"Dr. Frankenstein", "Dr. Jekyll", "Dr. Leonard McCoy" } l = frozenset({red, yellow, blue}) # binary types m = b"Archipelago" n = bytearray(7) o = memoryview(bytes(8)) # None type p = None # try using the type function with the variables to see what data type is returned print(type(a))

4. What is a class in Python?

Classes are code templates used to create objects using the class constructor. Objects contain data and functions that represent the properties of that object.

For example, you could have a class that represents a cat. Each cat has properties like color, weight, favorite food, etc. You can retrieve information about the cat stored in the cat object with functions like get_color() or get_weight().

Reflection time!: Can you think of a few examples drawn from real life where you could apply this information? What are other examples of classes and objects in your life?

5. What's the difference between a dictionary and a set in Python?

Both dictionaries and sets are collections or data structures that provide a way to store multiple values.

The main difference between them is that dictionaries can store key-value pairs with immutable values whereas sets can contain unique values that are mutable. Both sets and dictionaries are unordered collections of items.

Sets can be declared using the set() function, while dictionaries can be declared using the dict() function.

Reflection time!: How would you apply these two types of collection structures in a program? What are some practical examples that illustrate their similarities and differences?

6. What are Python modules?

A Python module is a .py file containing Python definitions and statements. Modules are often used to make larger programs easier to maintain. Instead of having to rewrite the same code, you can write a module containing a set of reusable functions to include in your application.

Note: You can easily make a Python module by saving your code with the .py file extension. Using the 'import' statement, you can import it into another project file.

7. What is a package in Python?

A Python package is a directory of modules that can be imported into another project. It is a standard way of distributing Python code. These modules contain Python code, including functions, classes, constants, variables, and more.

Note: Packages are sometimes referred to as libraries, and it's important to note that these are not the same as the Python standard library.

8. What is the Python standard library?

The Python standard library is the set of Python modules included with each version of Python and is not customizable by the end user.

It includes modules for things like parsing text, performing mathematical operations, and working with dates and times. It also includes modules for more complex tasks like networking and interacting with the OS. These modules provide basic functionality you can use in your code without needing to write your code from scratch.

The standard library is an important part of the Python language, and it's worth taking the time to get familiar with it.

9. What is the difference between a list and a tuple?

Lists and tuples represent sequences of values, but the main difference between a list and a tuple is that a list is mutable, and a tuple is immutable.

There are some more key differences as well.

Lists:

Lists have more memory
Elements of a list can be removed or replaced
Lists use square brackets []
Lists can be declared using the list() function.

Tuples

Tuples have less memory
Elements of a tuple cannot be removed or replaced
Tuples use parentheses ()
Tuples can be declared using the tuple() function.

Reflection time!: What are a few cases where you would want to use a tuple over a list and vice versa?

10. What is a Python namespace?

A namespace is a mapping from names to objects. Namespaces help organize variables and functions in Python. When objects are created, the object's address is assigned a namespace to help define its scope. This can prevent naming conflicts when your code base includes multiple libraries.

There are three types of namespaces:

Built-in namespaces contain functions of all the built-in objects in Python such as the abs() function.
Global namespaces are for variable names declared at the main level of a program, and exist until the interpreter terminates.
Local namespaces are for variable names declared on a local level, like classes, functions, loops, and other blocks of code.

Next steps for your interview preparation

That's all for this edition of Grokking Python!

We hope we've given you a taste of what you might encounter in an interview. Obviously, the universe of possible Python questions extends much further than the 10 we've included today. We'll return next month with an edition covering even more Python questions to help you prepare!

In the meantime, you can practice today's questions while working on Python coding problems and another area of the interview process that candidates often overlook: behavioral interviews.

As always, happy learning!

Grokking Python