Hiring guide for Python Engineers

Python Developer Hiring Guide

Python is a high-level, interpreted programming language that was created by Guido van Rossum and first released in 1991. It is designed with an emphasis on code readability, and its syntax allows programmers to express concepts in fewer lines of code than would be possible in languages such as C++ or Java. Python supports multiple programming paradigms, including procedural, object-oriented, and functional programming. It also provides a large standard library that includes areas like internet protocols, string operations, web services tools and operating system interfaces. Many third-party libraries are also available for Python which makes it applicable to a wide range of tasks such as web development, data analysis, artificial intelligence and machine learning. Python's simplicity and versatility have made it one of the most popular programming languages today.

Ask the right questions secure the right Python talent among an increasingly shrinking pool of talent.

First 20 minutes

General Python app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Python application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you explain the use of indentation in Python?
Indentation in Python is used to delimit blocks of code. Unlike other programming languages that use braces or keywords, Python uses indentation. This makes the code more readable and clean.
What are the basic data types in Python?
Python has several data types. These include numeric types like int, float, and complex, sequence types like list, tuple, and range, mapping type like dict, set types like set and frozenset, and boolean type bool.
Describe the difference between a list and a tuple in Python.
The main difference between lists and tuples in Python is that lists are mutable while tuples are immutable. This means that lists can be changed, and tuples cannot be changed. So, you would use a list when you want to contain items that may change, and a tuple when you want to contain items that won’t change.
How would you handle exceptions in Python?
Exceptions in Python can be handled using a try/except statement. The code that could potentially have an exception is put in the try block. The code that is executed if an error happens is put in the except block.
What are decorators in Python?
Decorators allow us to wrap another function in order to extend the behavior of the wrapped function, without permanently modifying it. In Python, decorators are implemented as functions or classes that take a function as an argument, and return a function.
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What you’re looking for early on

Has the candidate demonstrated a solid understanding of Python?
Does the candidate show good problem-solving skills?
Is the candidate familiar with Python frameworks such as Django or Flask?
Can the candidate effectively communicate technical information?

Next 20 minutes

Specific Python development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

Describe the difference between deep and shallow copy in Python.
Shallow copy is used when a new instance type gets created and it keeps the values that are copied in the new instance. Deep copy is used to store the values that are already copied. Deep copy doesn’t copy the reference pointers to the objects. It makes the reference to an object and the new object that is pointed by some other object gets stored.
How would you implement caching in Python?
Caching in Python can be implemented using the lru_cache decorator from the functools module. It allows us to specify how many results of the function we want to cache.
What are metaclasses in Python?
Metaclasses are the 'stuff' that creates classes. We define classes in order to create objects, right? But we create metaclasses in order to create classes. They are classes of classes.
Describe the difference between instance, static and class methods in Python.
Instance methods need a class instance and can access the instance through self. Class methods don’t need a class instance. They can’t access the instance (self) but they have access to the class itself via cls. Static methods don’t have access to cls or self. They work like regular functions but belong to the class’s namespace.
How would you implement multithreading in Python?
Multithreading in Python can be achieved using the threading module. We can create a new thread using threading.Thread() and use the start() method to start it. Python's Global Interpreter Lock (GIL) allows only one thread to execute at a time in a single process, so for CPU-bound tasks, it's better to use multiprocessing.
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The ideal back-end app developer

What you’re looking to see on the Python engineer at this point.

At this point, a skilled Python engineer should demonstrate strong problem-solving abilities, proficiency in Python programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Python.

What does the following Python code do? def greet(name): return 'Hello, ' + name
def greet(name):
	return 'Hello, ' + name
This code defines a function called 'greet' that takes one argument, 'name'. It concatenates 'Hello, ' with the 'name' argument and returns the result.
What will be the output of the following code? print(5 == 5.0)
print(5 == 5.0)
The output of this code will be 'True'. In Python, the '==' operator compares the values of the operands, not their types. So, 5 (an integer) is equal to 5.0 (a float) in value.
What does the following Python code do? def reverse_list(input_list): return input_list[::-1]
def reverse_list(input_list):
	return input_list[::-1]
This code defines a function called 'reverse_list' that takes a list as an argument and returns a new list which is the reverse of the input list. The '::-1' slice operation is used to reverse the list.
What does the following Python code do? import threading def print_numbers(): for i in range(10): print(i) t = threading.Thread(target=print_numbers) t.start()
import threading
def print_numbers():
	for i in range(10):
t = threading.Thread(target=print_numbers)
This code creates a new thread that executes the 'print_numbers' function concurrently with the rest of the program. The 'print_numbers' function simply prints the numbers from 0 to 9.

Wrap-up questions

Final candidate for Python Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Python application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are generators in Python?
Generators are a type of iterable, like lists or tuples. Unlike lists, they don’t allow indexing with arbitrary indices, but they can still be iterated through with for loops. They are created using functions and the yield statement.
Describe the difference between 'is' and '==' in Python.
'is' checks if both the variables point to the same object whereas '==' checks if the values for the two variables are the same. So, 'is' is for reference equality and '==' is for value equality.
How would you manage memory in Python?
Python's memory 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. 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.

Python application related

Product Perfect's Python development capabilities

Beyond hiring for your Python engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Python projects, and can engage in multiple capacities.