Top 10 Python Developer Interview Questions & Answers in 2024

1. Explain the Global Interpreter Lock (GIL) in Python and its impact on multi-threaded programs.

The Global Interpreter Lock (GIL) is a mechanism in CPython (the reference implementation of Python) that allows only one thread to execute Python bytecode at a time. This can impact the performance of multi-threaded programs, as it prevents multiple threads from executing Python code concurrently. However, it is important to note that the GIL only affects CPython and not other Python implementations like Jython or IronPython.

2. What is the difference between deep copy and shallow copy in Python?

A shallow copy creates a new object, but does not create copies of nested objects. It references the objects found in the original. In contrast, a deep copy creates a new object and recursively copies the objects found in the original, creating completely independent copies. The copy module in Python provides functions copy() for shallow copy and deepcopy() for deep copy.

3. How does Python's garbage collection work?

Python uses automatic memory management via a garbage collector to reclaim memory occupied by objects that are no longer in use. The primary mechanism is reference counting, where each object keeps track of how many references point to it. When an object's reference count drops to zero, the memory is freed. Additionally, Python also employs a cyclic garbage collector to detect and collect reference cycles.

4. Explain the use of decorators in Python with an example.

Decorators in Python are functions that modify the behavior of other functions. They are applied using the @decorator syntax. Here's a simple example of a decorator that logs the arguments and return value of a function:

def logger(func):
    def wrapper(*args, **kwargs):
        result = func(*args, **kwargs)
        print(f"Called {func.__name__} with args {args} and kwargs {kwargs}. Result: {result}")
        return result
    return wrapper

@logger
def add(a, b):
    return a + b

5. What is the Global Value Table (GVT) in Python's memory management?

The Global Value Table (GVT) is part of Python's memory management system. It maintains a table of all global variables in the program along with their values. This allows the garbage collector to identify and manage objects that are referenced by global variables. Understanding GVT is crucial for efficient memory management and preventing memory leaks in Python programs.

6. Explain the purpose of the if __name__ == "__main__": statement in Python scripts.

The if __name__ == "__main__": statement is used to check whether a Python script is being run as the main program or if it is being imported as a module into another script. It allows you to write code that will only be executed when the script is run directly and not when it is imported as a module. This is commonly used to define the main entry point for a Python script.

7. What is the Global Value Table (GVT) in Python's memory management?

The Global Value Table (GVT) is part of Python's memory management system. It maintains a table of all global variables in the program along with their values. This allows the garbage collector to identify and manage objects that are referenced by global variables. Understanding GVT is crucial for efficient memory management and preventing memory leaks in Python programs.

8. Discuss the differences between range and xrange in Python 2.

In Python 2, range returns a list, which can be memory-intensive for large ranges. xrange returns an xrange object, representing a range, but it generates values on-the-fly and does not create a list in memory. This makes xrange more memory-efficient for iterating over large ranges. In Python 3, range itself behaves like Python 2's xrange, and there is no separate xrange function.

9. Explain the purpose of the __slots__ attribute in Python classes.

The __slots__ attribute in Python classes is used to explicitly declare which attributes a class should have. It restricts the creation of new attributes at runtime, which can lead to reduced memory overhead and faster attribute access. However, it's essential to use __slots__ judiciously, as it can limit the flexibility of your classes.

10. How does the Global Positioning System (GPS) work, and how can you implement a simple GPS tracking system in Python?

GPS works by triangulating signals from multiple satellites to determine the receiver's location. Implementing a simple GPS tracking system in Python involves accessing a GPS module (such as a GPS receiver connected to a Raspberry Pi) to retrieve latitude, longitude, and other data. Libraries like gpsd can be used for interfacing with the GPS module, and the obtained data can be processed and displayed using mapping libraries like folium or geopy.