Python interview questions. Part III. Senior

Python interview questions. Part III. Senior

I am starting a series of posts about my own base of interviewing questions. Of course, it is not full and it doesn't have any answers and maybe some of the questions seem weird or even stupid, but I think they are good for finding the right candidate for Python position.

We all know that senior is not just a technical role that bound with years of experience and knowledge about his tools, they also have mentoring skills, some management skills in order to measure tasks and their time, and they tend to have some architecture skills etc. My questions here is only for technical side of Python senior developers.


Q: Is it possible to use the construction True = False? What about Python 2?

Q: When the else part of try...except...else will be executed?

Q: What is monkey patching? How to use it in Python? Give an example. Is it ever a good idea?

Q: How are dict and set implemented internally?

Q: What is MRO in Python? How does it work?

Q: Does Python have assignments(or assignment operator)?

Q: What is descriptor? Is there a difference between a descriptor and a decorator?

Q: How are arguments passed to function in Python - by value or by reference?

Q: What are the tools that help to find bugs or perform the static analysis? What static code analyzers do you know/used?

Q: Whenever Python exits, why isn’t all the memory de-allocated?

Q: Is it possible to have a producer thread reading from the network and a consumer thread writing to a file, really work in parallel? What about GIL?

Q: What is GIL? Why GIL is still existing?

Q: How to package code in Python? What package managers do you know?

Q: How to work with transitive dependencies in Python?

Q:What is wheels and eggs? What is the difference?

Q: How to package binary dependencies in Python?

Q: What is Cython? Why it exists?

Q: What are virtualenvs?

Q: Is Python a functional language? Specify the requirements for code written in a functional style.

Q: Identify the pitfalls/limitations in the function code.

Q: Explain how can you access a module written in Python from C? Vise versa?

Q: What advantages do NumPy arrays offer over (nested) Python lists?

Q: What is the process of compilation and linking in python?


Code involving questions

Q: Give an example of filter and reduce over an iterable object.

Q: You have a function that takes other function as an argument. How to validate the value of an argument?

Q: Explain how to reverse a Python generator?

Q: You need to implement a function that should use a static variable (for example, a call counter). You cannot write any code outside the function and you do not have information about external variables (outside your function). How to do it?

Q: You have a function that takes an argument that must be in given range [a, b]. Arrange the implementation options by speed at which they will perform.


    • argument in list [a, b]
    • a <= argument <= b
    • a in range (a, b + 1)

Q: What methods and in what order are called when print (A() + B()) is executed?

Q: What is the output?

    def Foo(): 
    	yield 42;
    	return 666

Q: What will be the output of the following code?

    >>> a = [[]]*3
    >>> a[1].append(1)
    >>> print(a)  # [[1], [1], [1]]


Q: Place the following functions below in order of their efficiency. How would you test your answer?

def f1(lIn):
    l1 = sorted(lIn)
    l2 = [i for i in l1 if i<0.5]
    return [i*i for i in l2]
def f2(lIn):
    l1 = [i for i in lIn if i<0.5]
    l2 = sorted(l1)
    return [i*i for i in l2]
def f3(lIn):
    l1 = [i*i for i in lIn]
    l2 = sorted(l1)
    return [i for i in l1 if i<(0.5*0.5)]

Q: Write a one-liner that will count the number of capital letters in a file. Your code should work even if the file is too big to fit in memory.

Q: Output? Why? Is this inheritance?

class C:
type (C ())
type (C)

Q: What's the output we get from running the following?

big_num_1   = 1000
big_num_2   = 1000
small_num_1 = 1
small_num_2 = 1
big_num_1 is big_num_2
small_num_1 is small_num_2

Q: How is this possible?

_MangledGlobal__mangled = 23
class MangledGlobal:
     def test(self):
         return __mangled

>>> MangledGlobal().test()

Q: What's the output?


Q: You saw the following piece of code. What is wrong with this code? Why is it needed?

    if __debug__:
    	assert False, ("error")

Q: What does the PYTHONOPTIMIZE flag do?


Python interview questions. Part I. Junior
Python interview questions. Part II. Middle

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