Python Coding challenge - Day 220 | What is the output of the following Python Code?

 

Let's break down and explain the function foo and the print statement:

Function Definition: foo

def foo(a, b, *args, **kwargs):

    return a + b + sum(args) + sum(kwargs.values())

Parameters:

1. a and b: These are positional parameters, meaning the first two arguments passed to foo will be assigned to a and b respectively.
2. *args: This parameter allows the function to accept an arbitrary number of additional positional arguments. These arguments are captured as a tuple named args.
3. **kwargs: This parameter allows the function to accept an arbitrary number of keyword arguments. These arguments are captured as a dictionary named kwargs.

Return Statement:

• a + b: This adds the values of a and b.
• sum(args): This calculates the sum of all additional positional arguments captured in args.
• sum(kwargs.values()): This calculates the sum of all the values of the keyword arguments captured in kwargs.

The function returns the sum of these three components.

Function Call and Print Statement:

print(foo(1, 2, 3, 4, x=5, y=6))

Arguments:

• 1 and 2: These are the first two positional arguments, so a = 1 and b = 2.
• 3 and 4: These are additional positional arguments, so args = (3, 4).
• x=5 and y=6: These are keyword arguments, so kwargs = {'x': 5, 'y': 6}.

Calculation:

1. a + b: $1+2=3$
2. sum(args): $3+4=7$
3. sum(kwargs.values()): $5+6=11$

Adding these together: $3+7+11=21$

Output:

The print statement will output 21.

So, when you run: print(foo(1, 2, 3, 4, x=5, y=6))

The output will be: 21

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How to Write Clean Code in Python?

 

Writing clean code in Python involves adhering to best practices that make your code readable, maintainable, and efficient. Here are some key principles and practices to help you write clean Python code:

1. Follow PEP 8

PEP 8 is the style guide for Python code. It covers a wide range of topics from naming conventions to indentation. Here are some highlights:

• Indentation: Use 4 spaces per indentation level.
• Maximum Line Length: Limit all lines to a maximum of 79 characters.
• Blank Lines: Use blank lines to separate top-level function and class definitions, and methods within classes.
• Imports: Group imports in the following order:
  1. Standard library imports.
  2. Related third-party imports.
  3. Local application/library-specific imports.
• Naming Conventions:
  • Function names should be lowercase, with words separated by underscores (snake_case).
  • Variable names should be lowercase, with words separated by underscores (snake_case).
  • Class names should use the CamelCase convention.

2. Write Meaningful Names

Choose descriptive and unambiguous names for variables, functions, classes, and modules.

# Bad a = 10 # Good timeout_seconds = 10

3. Keep Functions Small and Focused

A function should do one thing and do it well. If a function is too long or does multiple things, consider breaking it into smaller functions.

# Bad def process_data(data): # Process data clean_data = clean(data) # Analyze data result = analyze(clean_data) return result # Good def process_data(data): clean_data = clean(data) return analyze(clean_data) def clean(data): # Cleaning logic pass def analyze(clean_data): # Analysis logic pass

4. Use List Comprehensions and Generator Expressions

List comprehensions and generator expressions are concise and readable.

# Bad squares = [] for x in range(10): squares.append(x**2) # Good squares = [x**2 for x in range(10)]

5. Handle Exceptions Properly

Use exceptions to handle errors and exceptional cases. Avoid using exceptions for control flow.

# Bad try: value = my_dict[key] except KeyError: value = default_value # Good value = my_dict.get(key, default_value)

6. Use Docstrings

Write docstrings for all public modules, functions, classes, and methods. This helps others (and yourself) understand what your code does.

def add(a, b): """ Add two numbers and return the result. Parameters: a (int or float): The first number. b (int or float): The second number. Returns: int or float: The sum of the two numbers. """ return a + b

7. Avoid Global Variables

Global variables can lead to code that is difficult to debug and understand. Prefer local variables and function parameters.

8. Use Libraries and Built-in Functions

Leverage Python's standard library and built-in functions to write concise and efficient code.

# Bad result = [] for item in items: result.append(item.upper()) # Good result = list(map(str.upper, items))

9. Write Tests

Writing tests ensures that your code works as expected and helps prevent bugs.

import unittest def add(a, b): return a + b class TestMathFunctions(unittest.TestCase): def test_add(self): self.assertEqual(add(1, 2), 3) self.assertEqual(add(-1, 1), 0) self.assertEqual(add(-1, -1), -2) if __name__ == '__main__': unittest.main()

10. Refactor Regularly

Regularly refactor your code to improve readability and maintainability. This involves renaming variables, breaking down large functions, and simplifying complex logic.

Example of Clean Code

Here is an example of a clean Python function that adheres to these principles:

import math from typing import List def calculate_distances(points: List[tuple], origin: tuple = (0, 0)) -> List[float]: """ Calculate the Euclidean distances of a list of points from a given origin. Parameters: points (List[tuple]): A list of tuples representing points (x, y). origin (tuple): A tuple representing the origin point (default is (0, 0)). Returns: List[float]: A list of distances of the points from the origin. """ return [math.sqrt((x - origin[0])**2 + (y - origin[1])**2) for x, y in points] # Example usage points = [(1, 2), (3, 4), (5, 6)] distances = calculate_distances(points) print(distances) # Output: [2.23606797749979, 5.0, 7.810249675906654]

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Python Coding challenge - Day 219 | What is the output of the following Python Code?

 

The code snippet defines a function foo with three parameters: a, b, and c. The parameters b and c have default values of 5 and 10, respectively. Here's a detailed explanation of the function and its usage:

Function Definition

def foo(a, b=5, c=10):

    return a + b + c

a: This is a required positional parameter. It does not have a default value, so it must be provided when the function is called.

b: This parameter has a default value of 5. If the caller does not provide a value for b, it will default to 5.

c: This parameter has a default value of 10. If the caller does not provide a value for c, it will default to 10.

The function foo returns the sum of a, b, and c.

Function Call

print(foo(1, 2))

When the function foo is called with the arguments 1 and 2:

a is assigned the value 1 (from the first argument).

b is assigned the value 2 (from the second argument).

c is not provided, so it uses its default value of 10.

Thus, the function calculates the sum as follows:

a + b + c

1 + 2 + 10

13

Output

The print function outputs the result of the function call:

print(foo(1, 2))  # Output: 13

Summary

The foo function calculates the sum of its three parameters, using default values for b and c if they are not provided. In this specific call, foo(1, 2), it returns 13 because 1 + 2 + 10 equals 13.

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Python Coding challenge - Day 218 | What is the output of the following Python Code?

 

Code:

p = 256

q = 256

print(p is q)

r = 257

s = 257

print(r is s)

Solution and Explanation:

First Block:

p = 256

q = 256

print(p is q)

Variable Assignment:

p is assigned the value 256.

q is also assigned the value 256.

Integer Caching:

Python has a mechanism called integer caching where small integers (typically between -5 and 256, inclusive) are pre-allocated and reused. This means that any assignment of these integers will reference the same object in memory.

Identity Check (is operator):

When we do print(p is q), it checks if p and q refer to the same memory location.

Since 256 is within the integer caching range, both p and q refer to the same pre-allocated object.

Hence, p is q evaluates to True.

Second Block:

r = 257

s = 257

print(r is s)

Variable Assignment:

r is assigned the value 257.

s is also assigned the value 257.

Integer Caching:

257 is outside the typical integer caching range.

This means that r and s may not necessarily reference the same object in memory, even though they have the same value.

Identity Check (is operator):

When we do print(r is s), it checks if r and s refer to the same memory location.

Since 257 is not within the caching range, r and s will generally be different objects in memory.

Hence, r is s evaluates to False.

Summary

For small integers (typically -5 to 256), Python uses a single shared object to represent each integer value, resulting in is being True when comparing such integers.

For integers outside this range, Python creates separate objects, resulting in is being False when comparing such integers.

Output

The output of the provided code will be:

True

False

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Python Coding challenge - Day 217 | What is the output of the following Python Code?

 

The function foo is defined with a default argument x which is an empty list []. Here is the breakdown of the function and the output:

Function Definition

def foo(x=[]):

    x.append(1)

    return x

Key Points

• Default Argument: The default value of x is [], an empty list.
• Appending to List: Inside the function, 1 is appended to the list x.
• Returning the List: The modified list x is returned.

Default Mutable Arguments

In Python, default arguments are evaluated only once when the function is defined, not each time the function is called. This means that if the default argument is a mutable object like a list, and you modify this object, the changes will persist across function calls.

Execution

First Call:

print(foo())

foo is called without any arguments, so the default empty list [] is used.

1 is appended to the list, making it [1].

The list [1] is returned and printed.

Second Call:

print(foo())

foo is called again without any arguments.

This time, the same list (now [1] from the first call) is used as the default value.

1 is appended again, making the list [1, 1].

The list [1, 1] is returned and printed.

Output

Here is the complete code and its output:

def foo(x=[]):

    x.append(1)

    return x

print(foo())  # Output: [1]

print(foo())  # Output: [1, 1]

Explanation

First print(foo()):

The default list x is [].

1 is appended to x, resulting in [1].

[1] is printed.

Second print(foo()):

The default list x is now [1] (the same list used in the previous call).

1 is appended again, resulting in [1, 1].

[1, 1] is printed.

Conclusion

The key takeaway is that the default argument x=[] is not re-evaluated each time foo is called. Instead, the same list object is used across all calls to the function, leading to the list accumulating all the appended 1s over multiple calls.

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Download YouTube Videos using Python - pytube

 

Code:

from pytube import YouTube

# YouTube video URL

video_url = "https://www.youtube.com/watch?v=6VYtgkl3HPQ"

# Initialize a YouTube object

yt = YouTube(video_url)

# Select the highest resolution stream

stream = yt.streams.get_highest_resolution()

# Download the video

stream.download()

Explanantion:

This Python script uses the pytube library to download a YouTube video.

Let's break down the code:

Importing the necessary module:

from pytube import YouTube

This line imports the YouTube class from the pytube module, which provides functionality to interact with YouTube videos.

Defining the YouTube video URL:

video_url = "https://www.youtube.com/watch?v=6VYtgkl3HPQ"

Here, you specify the URL of the YouTube video you want to download. Replace "https://www.youtube.com/watch?v=6VYtgkl3HPQ" with the URL of the video you want to download.

Initializing a YouTube object:

yt = YouTube(video_url)

This line creates a YouTube object using the specified video URL. This object represents the YouTube video and allows you to access various properties and methods associated with the video.

Selecting the highest resolution stream:

stream = yt.streams.get_highest_resolution()

Here, you retrieve the stream with the highest resolution available for the video. The get_highest_resolution() method returns a Stream object representing the highest resolution stream.

Downloading the video:

stream.download()

Finally, you call the download() method on the Stream object to download the video. This method saves the video file to the current working directory with the default filename.

In summary, this script downloads the YouTube video specified by the video_url variable using the pytube library, selecting the highest resolution available.

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Python Coding challenge - Day 216 | What is the output of the following Python Code?

 

Code:

s = "hello"

t = s

s += " world"

print(s)

Solution and Explanation:

This code demonstrates the concept of mutable and immutable objects in Python, particularly focusing on strings.

Let's break it down step by step:

s = "hello": This line initializes a string variable s with the value "hello". Strings in Python are immutable, meaning once created, their contents cannot be changed.

t = s: This line creates another variable t and assigns it the same value as s. At this point, both s and t refer to the same string "hello".

s += " world": Here, a new string "hello world" is created by concatenating "hello" (the original value of s) with " world". However, since strings are immutable, this operation does not modify the existing string. Instead, it creates a new string and assigns it to s.

print(s): This line prints the value of s, which is now "hello world".

Now, let's see why t remains unchanged:

When t was assigned the value of s (t = s), it only received a reference to the original string "hello". Subsequent modifications to s do not affect t because t still refers to the original string "hello", which remains unchanged. Therefore, print(t) would output "hello".

This behavior occurs because strings are immutable in Python. If s were a mutable object, such as a list, modifying s would also affect t since they would both reference the same underlying object.

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Python Coding challenge - Day 215 | What is the output of the following Python Code?

 

Let's break down the code and understand what's happening step by step.

Code Breakdown:

a = (1, [2, 3], 4)

a[1].append(5)

print(a)

Step-by-Step Explanation:

Tuple Creation:

a = (1, [2, 3], 4)

Here, a is a tuple containing three elements: 1, [2, 3] (a list), and 4.

Tuples are immutable, meaning their elements cannot be changed directly. However, if a tuple contains a mutable object, like a list, the contents of that mutable object can be changed.

Modifying the List Inside the Tuple:

a[1].append(5)

a[1] accesses the second element of the tuple, which is the list [2, 3].

The append(5) method is called on this list, which modifies the list in place by adding 5 to the end.

After this operation, the list inside the tuple becomes [2, 3, 5].

Printing the Tuple:

print(a)

When print(a) is called, it prints the entire tuple.

The tuple now looks like this: (1, [2, 3, 5], 4).

Final Output:

The output of the code will be:

(1, [2, 3, 5], 4)

Detailed Explanation:

• Tuples are immutable: This means you cannot change, add, or remove elements directly in the tuple. However, if a tuple contains a mutable object (like a list), the contents of that object can be changed.
• Lists are mutable: Lists can be modified after their creation. You can add, remove, or change elements in a list.
• When a list inside a tuple is modified, the modification affects the list within the tuple. The tuple itself remains structurally unchanged, meaning the references it holds do not change, but the contents of the list referenced by the tuple can change.

This example illustrates the interplay between immutable and mutable types in Python and how modifying a mutable object within an immutable container affects the overall structure.

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5 Tricky Python code snippets

 1. Misleading Variable Scope

This snippet demonstrates the tricky nature of variable scope in Python, particularly with nested functions.

def outer_function():

    x = "outer"

    def inner_function():

        nonlocal x

        x = "inner"

        print("Inner x:", x)

    inner_function()

    print("Outer x:", x)

outer_function()

#clcoding.com

Inner x: inner

Outer x: inner

2. Mutable Default Arguments

This snippet shows the common pitfall of using mutable default arguments in function definitions.

def append_to_list(value, my_list=[]):

    my_list.append(value)

    return my_list

print(append_to_list(1))

print(append_to_list(2))

print(append_to_list(3))

#clcoding.com

[1]

[1, 2]

[1, 2, 3]

3. Unexpected Behavior with Floating Point Arithmetic

Floating-point arithmetic can be non-intuitive due to precision issues.

a = 0.1

b = 0.2

c = 0.3

print(a + b == c)  

print(f"{a + b:.17f}")  

#clcoding.com

False

0.30000000000000004

4. Changing a List While Iterating

This snippet demonstrates the pitfalls of modifying a list while iterating over it.

numbers = [1, 2, 3, 4, 5]

for i in numbers:

    if i % 2 == 0:

        numbers.remove(i)

print(numbers)

#clcoding.com

[1, 3, 5]

5. Unpacking and Extended Unpacking

Python allows for complex unpacking operations which can be tricky to understand at first glance.

a, b, *c, d = range(6)

print(a)  

print(b)  

print(c)  

print(d)  

# Nested unpacking

x, (y, z) = (1, (2, 3))

print(x)  

print(y) 

print(z)  

#clcoding.com

0

1

[2, 3, 4]

5

1

2

3

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Python Coding challenge - Day 214 | What is the output of the following Python Code?

 

Code: 

a = 0.1

b = 0.2

c = 0.3

print(a + b == c) 

Solution and Explanation:

The code snippet:

a = 0.1

b = 0.2

c = 0.3

print(a + b == c)

produces False as output. This result can be surprising, but it stems from the way floating-point numbers are represented in computer hardware. Here’s a detailed explanation:

Floating-Point Representation

Binary Representation:

Computers represent floating-point numbers in binary (base-2) format, which can lead to precision issues because not all decimal fractions can be represented exactly as binary fractions.

For example, 0.1 in binary is an infinitely repeating sequence: 0.00011001100110011....

Precision Limitations:

When 0.1 and 0.2 are stored in a computer's memory, they are approximated to the nearest value that can be represented in the finite number of bits available.

The same approximation happens for 0.3.

Summation Inaccuracy:

When adding 0.1 and 0.2, the result is not exactly 0.3 due to these approximations. Instead, the result is a value very close to 0.3, but not exactly 0.3.

The actual value of a + b might be something like 0.30000000000000004.

Comparison:

When Python compares a + b to c, it is comparing 0.30000000000000004 (the result of a + b) to 0.3 (the stored value of c), and since these are not exactly equal, the comparison returns False.

Demonstration with More Precision

You can observe this behavior by printing the values with higher precision:

print(f"{a + b:.17f}")  # Shows the precision error

print(f"{c:.17f}")

This will output:

0.30000000000000004

0.29999999999999999

As you can see, the two numbers are very close but not exactly the same, which explains why the comparison a + b == c evaluates to False.

Best Practices

To avoid issues with floating-point comparisons:

Use a Tolerance:

Instead of direct comparison, use a small tolerance value to check if the numbers are "close enough":

tolerance = 1e-10

print(abs((a + b) - c) < tolerance)  # True

Decimal Module:

For financial and other high-precision calculations, use Python's decimal module which can handle decimal arithmetic more accurately.

from decimal import Decimal

a = Decimal('0.1')

b = Decimal('0.2')

c = Decimal('0.3')

print(a + b == c)  # True

This approach avoids the pitfalls of floating-point arithmetic by using a representation that can exactly represent decimal fractions.

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Python 201: Intermediate Python

Python 201 is the sequel to my first book, Python 101. If you already know the basics of Python and now you want to go to the next level, then this is the book for you! This book is for intermediate level Python programmers only. There won't be any beginner chapters here. This book is based on Python 3.

The book will be broken up into five parts. Here's how:

Part I - Intermediate Modules

Chapter 1 - The argparse module

Chapter 2 - The collections module

Chapter 3 - The contextlib module (Context Managers)

Chapter 4 - The functools module (Function overloading, caching, etc)

Chapter 5 - All about imports

Chapter 6 - The importlib module

Chapter 7 - Iterators and Generators

Chapter 8 - The itertools module

Chapter 9 - The re module (An Intro to Regex in Python)

Chapter 10 - The typing module (Type Hinting)

Part II - Odds and Ends

Chapter 11 - map, filter and more

Chapter 12 - unicode

Chapter 13 - benchmarking

Chapter 14 - encryption

Chapter 15 - Connecting to databases

Chapter 16 - super

Chapter 17 - descriptors

Chapter 18 - Scope (local, global and the new non_local)

Part III - Web

Chapter 19 - Web scraping

Chapter 20 - Working with web APIs

Chapter 21 - ftplib

Chapter 22 - urllib

Part IV - Testing

Chapter 23 - Doctest

Chapter 24 - unittest

Chapter 25 - mock

Chapter 26 - coverage.py

Part V - Concurrency

Chapter 27 - The asyncio module

Chapter 28 - The threading module

Chapter 29 - The multiprocessing module

Chapter 30 - The concurrent.futures module

Join the course: Python 201: Intermediate Python

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Convert to mathematical symbols using Python 🧵

 

import math

import latexify

@latexify.function

def quadratic_roots(a, b, c):

    discriminant = b ** 2 - 4 * a * c

    root1 = (-b + math.sqrt(discriminant)) / (2 * a)

    root2 = (-b - math.sqrt(discriminant)) / (2 * a)

    return root1, root2

quadratic_roots

#clcoding.com

import math

import latexify

@latexify.function

def pythagorean_theorem(a, b):

    return math.sqrt(a ** 2 + b ** 2)

pythagorean_theorem

#clcoding.com

import math

import latexify

@latexify.function

def compound_interest(P, r, n, t):

    return P * (1 + r/n) ** (n*t)

compound_interest

#clcoding.com

import math

import latexify

@latexify.function

def distance(x1, y1, x2, y2):

  return math.sqrt((x2-x1)**2 + (y2-y1)**2)

distance

import math

import latexify

@latexify.function

def factorial(n):

  if n == 0:

    return 1

  elif n == 1:

    return 1

  else:

    return n * factorial(n-1)

factorial

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Python Coding challenge - Day 213 | What is the output of the following Python Code?

 

Code:

a = [1, 2, 3, 4]

b = [1, 2, 5]

if sorted(a) < sorted(b):

    print(True)

else:

    print(False)

Solution and Explanation: 

Let's break down the code step by step to understand what it does:

List Initialization:

a = [1, 2, 3, 4]

b = [1, 2, 5]

Here, two lists a and b are initialized with the values [1, 2, 3, 4] and [1, 2, 5], respectively.

Sorting the Lists:

sorted(a)

sorted(b)

The sorted() function is used to sort the lists a and b. However, since both lists are already sorted in ascending order, the sorted versions will be the same as the original:

sorted(a) results in [1, 2, 3, 4]

sorted(b) results in [1, 2, 5]

Comparison:

sorted(a) < sorted(b)

In Python, comparing lists using < compares them lexicographically (element by element from left to right, like in a dictionary). The comparison proceeds as follows:

Compare the first elements: 1 (from a) and 1 (from b). Since they are equal, move to the next element.

Compare the second elements: 2 (from a) and 2 (from b). Since they are equal, move to the next element.

Compare the third elements: 3 (from a) and 5 (from b). Since 3 is less than 5, the comparison sorted(a) < sorted(b) evaluates to True.

Conditional Statement:

if sorted(a) < sorted(b):

    print(True)

else:

    print(False)

Given that sorted(a) < sorted(b) is True, the code enters the if block and executes print(True).

Putting it all together, the code prints True because, when compared lexicographically, the sorted list a ([1, 2, 3, 4]) is indeed less than the sorted list b ([1, 2, 5]).

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13 Powerful Python Features You're Probably Not Using Enough

Python is a versatile and powerful language, and while many developers use it extensively, there are numerous features that often go underutilized.

List Comprehensions

List comprehensions provide a concise way to create lists. This can replace the need for using loops to generate lists.

squares = [x**2 for x in range(10)]

Generator Expressions

Similar to list comprehensions but with parentheses, generator expressions are used for creating generators. These are memory-efficient and suitable for large data sets.

squares_gen = (x**2 for x in range(10))

Default Dictionary

The defaultdict from the collections module is a dictionary-like class that provides default values for missing keys.

from collections import defaultdict

dd = defaultdict(int)

dd['key'] += 1

Named Tuples

namedtuple creates tuple subclasses with named fields. This makes code more readable by accessing fields by name instead of position.

from collections import namedtuple

Point = namedtuple('Point', 'x y')

p = Point(10, 20)

Enumerate Function

The enumerate function adds a counter to an iterable and returns it as an enumerate object. This is useful for obtaining both the index and the value in a loop.

for index, value in enumerate(['a', 'b', 'c']):

    print(index, value)

Zip Function

The zip function combines multiple iterables into a single iterable of tuples. This is useful for iterating over multiple sequences simultaneously.

names = ['a', 'b', 'c']

ages = [20, 25, 30]

combined = list(zip(names, ages))

Set Comprehensions

Similar to list comprehensions, set comprehensions create sets in a concise way.

unique_squares = {x**2 for x in range(10)}

Frozenset

A frozenset is an immutable set. It's useful when you need a set that cannot be changed after creation.

fs = frozenset([1, 2, 3, 2, 1])

Counter

The Counter class from the collections module counts the occurrences of elements in a collection. It's useful for counting hashable objects.

from collections import Counter

counts = Counter(['a', 'b', 'c', 'a', 'b', 'b'])

Context Managers

Using the with statement, context managers handle resource management, like file I/O, efficiently and cleanly.

with open('file.txt', 'r') as file:

    contents = file.read()

dataclass

The dataclass decorator simplifies class creation by automatically adding special methods like init and repr.

from dataclasses import dataclass

@dataclass

class Point:

    x: int

    y: int

Decorators

Decorators are functions that modify the behavior of other functions. They are useful for logging, access control, memoization, and more.

def my_decorator(func):

    def wrapper():

        print("Something is happening before the function is called.")

        func()

        print("Something is happening after the function is called.")

    return wrapper

@my_decorator

def say_hello():

    print("Hello!")

Asyncio

The asyncio module provides a framework for asynchronous programming. This is useful for I/O-bound and high-level structured network code.

import asyncio

async def main():

    print('Hello')

    await asyncio.sleep(1)

    print('World')

asyncio.run(main())

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