10 Advanced Python Interview Questions

Nail your next interview

Image provided by the author.

With Python becoming more and more popular lately, many of you are probably undergoing technical interviews dealing with Python right now. In this post, I will list ten advanced Python interview questions and answers.

These can be confusing and are directed at mid-level developers, who need an excellent understanding of Python as a language and how it works under the hood.

What Are Nolocal and Global Keywords Used For?

These two keywords are used to change the scope of a previously declared variable. nolocal is often used when you need to access a variable in a nested function:

def func1(): 
    x = 5
    def func2(): 
        nolocal x 
        print(x) 
    func2()

global is a more straightforward instruction. It makes a previously declared variable global. For example, consider this code:

x = 5 
def func1(): 
    print(x) 
func1() 
> 5

Since x is declared before the function call, func1 can access it. However, if you try to change it:

x = 5 
def func2(): 
    x += 3 
func2() 
> UnboundLocalError: local variable 'c' referenced before assignment

To make it work, we need to indicate that by x we mean the global variable x:

x = 5 
def func2(): 
    global x 
    x += 3 
func2()

What Is the Difference Between Classmethod and Staticmethod?

Both of them define a class method that can be called without instantiating an object of the class. The only difference is in their signature:

class A: 
    @staticmethod 
    def func1(): 
        pass 
    @classmethod 
    def func2(cls): 
        pass

As you can see, the classmethod accepts an implicit argument cls, which will be set to the class A itself. One common use case for classmethod is creating alternative inheritable constructors.

What Is GIL and What Are Some of the Ways to Get Around It?