Python Tips 01
This page keeps a "scattered but useful" style, collecting small tips that don't deserve their own full chapter but are great for quick reference later.
sorted() sorts in ascending order by default
numbers = [3, 1, 4, 1, 5, 9]
print(sorted(numbers))
print(sorted(numbers, reverse=True))
Use list.sort() for in-place sorting
numbers = [3, 1, 4]
numbers.sort()
sorted() returns a new list; sort() modifies in place.
Checking if two lists contain the same elements
If order doesn't matter:
list1 = [3, 2, 1]
list2 = [1, 2, 3]
print(sorted(list1) == sorted(list2))
If you also care about duplicate counts:
from collections import Counter
list1 = [1, 2, 2, 3]
list2 = [3, 2, 1, 2]
print(Counter(list1) == Counter(list2))
ord() and chr()
print(ord("a")) # 97
print(chr(97)) # a
These are common in character encoding, input processing for competitive programming, and simple mapping tasks.
key= is the core of sorting
words = ["apple", "kiwi", "banana"]
print(sorted(words, key=len))
Whenever you need to sort by length, by field, or by a custom rule, think of key= first.