50 Most Commonly Used Python Code Snippets for Everyday Programming

Python, owing to its simplicity and expressiveness, remains one of the most loved programming languages in the world. Whether you are a beginner or a seasoned developer, having a handy set of frequently used code snippets can save considerable time. This article presents 50 widely used Python code snippets, categorised for clarity and practical use.

🔁 List Operations

1. List Comprehension with Condition

squares = [x**2 for x in range(10) if x % 2 == 0]

2. Flatten a Nested List

nested = [[1, 2], [3, 4]]
flat = [item for sublist in nested for item in sublist]

3. Remove Duplicates from a List

unique_items = list(set(my_list))

4. Reverse a List

reversed_list = my_list[::-1]

5. Sort List of Dictionaries by Key

sorted_list = sorted(dicts_list, key=lambda x: x['key_name'])

📁 File Handling

6. Read a File

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

7. Write to a File

with open('file.txt', 'w') as file:
    file.write('Hello, World!')

8. Append to a File

with open('file.txt', 'a') as file:
    file.write('\nAppended line.')

9. Read a File Line by Line

with open('file.txt', 'r') as file:
    for line in file:
        print(line.strip())

10. Check if File Exists

import os
exists = os.path.isfile('file.txt')

🔍 String Manipulation

11. Reverse a String

reversed_str = my_string[::-1]

12. Check for Palindrome

is_palindrome = my_string == my_string[::-1]

13. Count Occurrences of a Substring

count = my_string.count('substring')

14. Replace Substring

new_string = my_string.replace('old', 'new')

15. Split String into List

words = my_string.split()

📏 Mathematical Operations

16. Calculate Factorial

import math
result = math.factorial(5)

17. Generate Fibonacci Sequence

def fibonacci(n):
    a, b = 0, 1
    for _ in range(n):
        yield a
        a, b = b, a + b

18. Check for Prime Number

def is_prime(n):
    return n > 1 and all(n % i for i in range(2, int(n**0.5) + 1))

19. Find GCD of Two Numbers

import math
gcd = math.gcd(a, b)

20. Calculate Square Root

import math
sqrt = math.sqrt(16)

📊 Data Structures

21. Merge Two Dictionaries

merged_dict = {**dict1, **dict2}

22. Invert a Dictionary

inverted = {v: k for k, v in original.items()}

23. Create Dictionary from Two Lists

dict_from_lists = dict(zip(keys, values))

24. Count Frequency of Elements

from collections import Counter
freq = Counter(my_list)

25. Sort Dictionary by Value

sorted_dict = dict(sorted(my_dict.items(), key=lambda item: item[1]))

🧪 Conditionals and Loops

26. Ternary Conditional Operator

result = 'Yes' if condition else 'No'

27. Enumerate in Loop

for index, value in enumerate(my_list):
    print(index, value)

28. Zip Multiple Lists

for a, b in zip(list1, list2):
    print(a, b)

29. List Comprehension with Multiple Conditions

result = [x for x in range(100) if x % 2 == 0 and x % 5 == 0]

30. Nested Loops in List Comprehension

pairs = [(x, y) for x in list1 for y in list2]

🛠️ Utilities

31. Measure Execution Time

import time
start = time.time()
# code block
end = time.time()
print(f"Execution Time: {end - start}")

32. Shuffle a List

import random
random.shuffle(my_list)

33. Generate Random Number

import random
num = random.randint(1, 100)

34. Check if List is Empty

if not my_list:
    print("List is empty")

35. Swap Two Variables

a, b = b, a

📦 Modules and Packages

36. Install Package via pip

pip install package_name

37. Import Module with Alias

import numpy as np

38. Handle Import Errors

try:
    import module
except ImportError:
    # handle error

39. List Installed Packages

pip list

40. Get Current Working Directory

import os
cwd = os.getcwd()

🧰 Advanced Techniques

41. Lambda Function

square = lambda x: x * x

42. Map Function

squares = list(map(lambda x: x**2, my_list))

43. Filter Function

evens = list(filter(lambda x: x % 2 == 0, my_list))

44. Reduce Function

from functools import reduce
product = reduce((lambda x, y: x * y), my_list)

45. List All Attributes of an Object

attributes = dir(object)

🗒️ Miscellaneous

46. Check Data Type

type_of_var = type(variable)

47. Convert String to Integer

num = int('123')

48. Convert Integer to String

s = str(123)

49. Format String with f-Strings

name = 'Alice'
greeting = f'Hello, {name}!'

50. Use of Any and All

any_true = any([False, True, False])
all_true = all([True, True, True])

These code snippets are practical, often used in day-to-day tasks, and should be part of every Python developer's toolkit. Feel free to bookmark or adapt them to your projects.