30‑Second Python Snippets That Unlock Powerful Programming Tricks

30‑Second Python Snippets

Today we share a handful of Python code snippets that can be learned in about 30 seconds. Each snippet demonstrates a useful programming idea, is easy to understand, and can be applied in many contexts.

1. 2D List

Given a width, height, and optional initial value, return a two‑dimensional list.

def initialize_2d_list(w, h, val=None):
    return [[val for x in range(w)] for y in range(h)]

Example:

>> initialize_2d_list(2, 2)
[[None, None], [None, None]]
>>> initialize_2d_list(2, 2, 0)
[[0, 0], [0, 0]]

2. Function Split Array

Apply a predicate function to each element of a list and split the list into two parts: elements for which the function returns True and those for which it returns False.

def bifurcate_by(lst, fn):
    return [
        [x for x in lst if fn(x)],
        [x for x in lst if not fn(x)]
    ]

Example:

>> bifurcate_by(['beep', 'boop', 'foo', 'bar'], lambda x: x[0] == 'b')
[['beep', 'boop', 'bar'], ['foo']]

3. Intersection By

Return the elements from the first list that have matching values in the second list according to a mapping function.

def intersection_by(a, b, fn):
    _b = set(map(fn, b))
    return [item for item in a if fn(item) in _b]

Example:

>> from math import floor
>>> intersection_by([2.1, 1.2], [2.3, 3.4], floor)
[2.1]

4. Max Value Index

Return the index of the maximum element in a list.

def max_element_index(arr):
    return arr.index(max(arr))

Example:

>> max_element_index([5, 8, 9, 7, 10, 3, 0])
4

5. Symmetric Difference

Return the elements that appear in only one of the two lists.

def symmetric_difference(a, b):
    _a, _b = set(a), set(b)
    return [item for item in a if item not in _b] + [item for item in b if item not in _a]

Example:

>> symmetric_difference([1, 2, 3], [1, 2, 4])
[3, 4]

6. Clamp Number

Clamp a number to stay within a given range.

def clamp_number(num, a, b):
    return max(min(num, max(a, b)), min(a, b))

Examples:

>> clamp_number(2, 3, 10)
3
>>> clamp_number(7, 3, 10)
7
>>> clamp_number(124, 3, 10)
10

7. Map Values

Create a new dictionary by applying a function to each value of the original dictionary.

def map_values(obj, fn):
    ret = {}
    for key in obj.keys():
        ret[key] = fn(obj[key])
    return ret

Example:

>> users = {'fred': {'user': 'fred', 'age': 40}, 'pebbles': {'user': 'pebbles', 'age': 1}}
>>> map_values(users, lambda u: u['age'])
{'fred': 40, 'pebbles': 1}
>>> map_values(users, lambda u: u['age'] + 1)
{'fred': 41, 'pebbles': 2}

8. Decapitalize

Lowercase the first character of a string; optionally uppercase the rest.

def decapitalize(s, upper_rest=False):
    return s[:1].lower() + (s[1:].upper() if upper_rest else s[1:])

Examples:

>> decapitalize('FooBar')
'fooBar'
>>> decapitalize('FooBar', True)
'fOOBAR'

9. Sum By

Sum the results of applying a function to each element of a list.

def sum_by(lst, fn):
    return sum(map(fn, lst))

Example:

>> sum_by([{'n': 4}, {'n': 2}, {'n': 8}], lambda v: v['n'])
14

10. Count Occurrences

Count how many times a specific value appears in a list (type‑matched).

def count_occurrences(lst, val):
    return len([x for x in lst if x == val and type(x) == type(val)])

Example:

>> count_occurrences([1, 1, 2, 1, 2, 3], 1)
3

11. Chunk (Array Re‑group)

Split a list into sub‑lists of a given size; the last chunk may contain fewer elements.

def chunk(lst, size):
    return [lst[i:i+size] for i in range(0, len(lst), size)]

Example:

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

12. Digitize (Number to Array)

Convert an integer into a list of its digits.

def digitize(n):
    return list(map(int, str(n)))

Example:

>> digitize(123)
[1, 2, 3]

13. Non‑Recursive Fibonacci

Generate the Fibonacci sequence up to the n‑th index without recursion.

def fibonacci(n):
    a, b = 0, 1
    result = [a]
    for _ in range(n):
        result.append(b)
        a, b = b, a + b
    return result

Example:

>> fibonacci(7)
[0, 1, 1, 2, 3, 5, 8, 13]

14. Snake Case Conversion

Convert any string to snake_case, handling spaces, hyphens, and camelCase.

def snake(s):
    import re
    s = re.sub(r'[-\s]+', '_', s)
    s = re.sub(r'([A-Z]+)', r' \1', s)
    s = re.sub(r'([A-Z][a-z]+)', r' \1', s)
    return '_'.join(s.lower().split())

Examples:

>> snake('camelCase')
'camel_case'
>>> snake('some text')
'some_text'
>>> snake('some-mixed_string With spaces_underscores-and-hyphens')
'some_mixed_string_with_spaces_underscores_and_hyphens'
>>> snake('AllThe-small Things')
'all_the_small_things'

This collection of short, practical Python functions can boost productivity and deepen understanding of common programming patterns.