Cookbooks
Practical recipes for real-world Python programming tasks.
How to Convert a String to an Integer in Python
Convert strings to integers using int() with error handling for invalid input.
How to check if a key exists in a dictionary in Python
Check if a dictionary key exists using in, .get(), or catching KeyError. The in operator is the most Pythonic.
How to flatten a nested list in Python
Flatten a nested list using list comprehension, itertools, or recursion.
How to count occurrences of an item in a list in Python
Count how many times an element appears in a list using list.count(), Counter, or a manual loop.
How to get the current date and time in Python
Get the current date and time using datetime.now() or timezone-aware datetime with zoneinfo. Also covers date only and time only.
How to read a file line by line in Python
Read a file line by line using for loops, readlines(), or iter(). Compare memory efficiency and use cases.
How to find the maximum value in a list in Python
Find the maximum value in a list using max(), sorted(), or a loop. Includes handling empty lists and custom objects.
How to Generate a Random Number in Python
Generate random numbers using the random module — integers, floats, and within ranges.
How to merge two dictionaries in Python
Merge dictionaries using the | operator, ** unpacking, or .update(). The | operator is the cleanest for Python 3.9+.
How to Join a List into a String in Python
Learn how to convert a list to a string in Python using str.join, with examples for strings, numbers, custom separators, and edge cases.
How to remove duplicates from a list in Python
Remove duplicates while preserving order using dict.fromkeys() or a loop. The simplest solution is list(dict.fromkeys(items)).
How to reverse a string in Python
Reverse a string using slicing or reversed(). The fastest method is slicing with [::-1].
How to total a CSV column with csv.DictReader
Read a CSV file with csv.DictReader and total one column in Python with a simple loop.
How to sort a list by a key in Python
Sort lists by custom criteria using the key parameter in sorted() and list.sort().
How to Swap Two Variables in Python
Swap two variables in Python using tuple unpacking or a temporary variable. Tuple unpacking is the most Pythonic way.
How to write to a file in Python
Write text or binary data to files using Python built-in open function with different modes.