Hiring guide for Cython Engineers

Cython Developer Hiring Guide

Cython is a programming language designed to bridge the gap between Python and C/C++. It was developed by Robert Bradshaw, Stefan Behnel, Dag Sverre Seljebotn, Greg Ewing and others in 2007 as an optimization to Python's execution speed. Cython allows for both static and dynamic typing, enabling developers to write C extensions for Python in a more straightforward manner. The language has been widely adopted due its ability to handle computationally intensive tasks with ease. Its development is open-source under the Apache License which encourages community contributions.

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

First 20 minutes

General Cython app knowledge and experience

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

How would you install Cython on your system?
You can install Cython using pip, the Python package installer. The command is 'pip install Cython'.
What are the main benefits of using Cython?
Cython can increase the execution speed of Python code and allow the calling of C functions. It also provides type safety.
Describe the difference between Python and Cython.
Python is an interpreted language while Cython is a programming language that aims to be a superset of Python to also include calling C functions and declaring C types on variables and class attributes.
How would you compile a Cython file?
You can compile a Cython file by using the command 'cython filename.pyx' which will generate a .c file. You then compile this .c file with a C compiler.
What are the ways to declare C variables in Cython?
C variables can be declared in Cython using the 'cdef' keyword followed by the type and the variable name.
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What you’re looking for early on

Does the candidate have a strong understanding of both Python and C?
Has the candidate demonstrated experience with Cython-specific concepts?
Can the candidate effectively debug Cython code?
Is the candidate familiar with the process of optimizing Python code with Cython?

Next 20 minutes

Specific Cython 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.

How would you call a C function from a Cython file?
You can call a C function from a Cython file by using the 'cdef extern' keyword to declare the function and then simply call it as you would in Python.
Describe the difference between 'cdef' and 'cpdef' in Cython.
'cdef' is used to declare C variables, functions, and classes. 'cpdef' is used to declare C functions that can be called from Python and C.
What is the role of the 'pyx' file extension in Cython?
The 'pyx' file extension is used for Cython source files. These files contain code that is a mix of Python and C.
How would you improve the performance of Python code using Cython?
You can improve the performance of Python code using Cython by declaring types for variables, converting Python classes to C classes, and calling C functions directly.
What are the limitations of using Cython?
One limitation of Cython is that it can make the code harder to read and write. It also requires a compilation step which makes the development process slower.
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The ideal back-end app developer

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

At this point, a skilled Cython engineer should demonstrate strong problem-solving abilities, proficiency in Cython 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 Cython.

What does this simple Cython code do?
def add_numbers(int a, int b):
    return a + b
This code defines a function in Cython that adds two integers together and returns the result.
What does the 'cdef' keyword do in this Cython code?
cdef int a = 5
The 'cdef' keyword is used to declare C variables. In this code, it is used to declare an integer 'a' with a value of 5.
What will be the output of this Cython code that manipulates an array?
cdef int[:] arr = [1, 2, 3, 4, 5]
arr[2] = 10
This code will output the array [1, 2, 10, 4, 5]. It creates an array and then changes the third element to 10.
What does this Cython code do that involves threading?
from cython.parallel import prange
cdef int i
for i in prange(5, nogil=True):
This code uses the 'prange' function from the 'cython.parallel' module to create a parallel for loop that runs 5 iterations concurrently. It prints the index of each iteration.

Wrap-up questions

Final candidate for Cython 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 Cython application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

Describe the difference between 'cdef' and 'def' functions in Cython.
'cdef' functions are C functions and can't be called from Python, while 'def' functions are Python functions and can be called from both Python and C.
How would you handle exceptions in Cython?
Exceptions in Cython can be handled using the same 'try' and 'except' blocks as in Python. Cython also supports the 'finally' block.
What is the purpose of the 'cimport' statement in Cython?
The 'cimport' statement is used to import C functions, types, and variables from .pxd files.

Cython application related

Product Perfect's Cython development capabilities

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