Curated collection of useful Python snippets that you can understand in 30 seconds or less.

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Check if all elements in a list are equal.

Use [1:] and [:-1] to compare all the values in the given list.

def all_equal(lst): return lst[1:] == lst[:-1]

all_equal([1, 2, 3, 4, 5, 6]) # False all_equal([1, 1, 1, 1]) # True

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Returns True if all the values in a flat list are unique, False otherwise.

Use set() on the given list to remove duplicates, compare its length with the length of the list.

def all_unique(lst): return len(lst) == len(set(lst))

x = [1,2,3,4,5,6] y = [1,2,2,3,4,5] all_unique(x) # True all_unique(y) # False

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Splits values into two groups. If an element in filter is True, the corresponding element in the collection belongs to the first group; otherwise, it belongs to the second group.

Use list comprehension and enumerate() to add elements to groups, based on filter.

def bifurcate(lst, filter): return [ [x for i,x in enumerate(lst) if filter[i] == True], [x for i,x in enumerate(lst) if filter[i] == False] ]

bifurcate(['beep', 'boop', 'foo', 'bar'], [True, True, False, True]) # [ ['beep', 'boop', 'bar'], ['foo'] ]

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Splits values into two groups according to a function, which specifies which group an element in the input list belongs to. If the function returns True, the element belongs to the first group; otherwise, it belongs to the second group.

Use list comprehension to add elements to groups, based on fn.

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

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

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Chunks a list into smaller lists of a specified size.

Use list() and range() to create a list of the desired size. Use map() on the list and fill it with splices of the given list. Finally, return use created list.

from math import ceil def chunk(lst, size): return list( map(lambda x: lst[x * size:x * size + size], list(range(0, ceil(len(lst) / size)))))

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

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Removes falsey values from a list.

Use filter() to filter out falsey values (False, None, 0, and "").

def compact(lst): return list(filter(bool, lst))

compact([0, 1, False, 2, '', 3, 'a', 's', 34]) # [ 1, 2, 3, 'a', 's', 34 ]

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Groups the elements of a list based on the given function and returns the count of elements in each group.

Use map() to map the values of the given list using the given function. Iterate over the map and increase the element count each time it occurs.

def count_by(arr, fn=lambda x: x): key = {} for el in map(fn, arr): key[el] = 0 if el not in key else key[el] key[el] += 1 return key

from math import floor count_by([6.1, 4.2, 6.3], floor) # {4: 1, 6: 2} count_by(['one', 'two', 'three'], len) # {3: 2, 5: 1}

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Counts the occurrences of a value in a list.

Increment a counter for every item in the list that has the given value and is of the same type.

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

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

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Deep flattens a list.

Use recursion. Define a function, spread, that uses either list.extend() or list.append() on each element in a list to flatten it. Use list.extend() with an empty list and the spread function to flatten a list. Recursively flatten each element that is a list.

def spread(arg): ret = [] for i in arg: if isinstance(i, list): ret.extend(i) else: ret.append(i) return ret def deep_flatten(lst): result = [] result.extend( spread(list(map(lambda x: deep_flatten(x) if type(x) == list else x, lst)))) return result

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

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Returns the difference between two iterables.

Create a set from b, then use list comprehension on a to only keep values not contained in the previously created set, _b.

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

difference([1, 2, 3], [1, 2, 4]) # [3]

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Returns the difference between two lists, after applying the provided function to each list element of both.

Create a set by applying fn to each element in b, then use list comprehension in combination with fn on a to only keep values not contained in the previously created set, _b.

def difference_by(a, b, fn): _b = set(map(fn, b)) return [item for item in a if fn(item) not in _b]

from math import floor difference_by([2.1, 1.2], [2.3, 3.4],floor) # [1.2] difference_by([{ 'x': 2 }, { 'x': 1 }], [{ 'x': 1 }], lambda v : v['x']) # [ { x: 2 } ]

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Returns True if the provided function returns True for every element in the list, False otherwise.

Iterate over the elements of the list to test if every element in the list returns True based on fn. Omit the seconds argument, fn, to check if all elements are True.

def every(lst, fn=lambda x: not not x): for el in lst: if not fn(el): return False return True

every([4, 2, 3], lambda x: x > 1) # True every([1, 2, 3]) # True

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Returns every nth element in a list.

Use [1::nth] to create a new list that contains every nth element of the given list.

def every_nth(lst, nth): return lst[1::nth]

every_nth([1, 2, 3, 4, 5, 6], 2) # [ 2, 4, 6 ]

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Filters out the non-unique values in a list.

Use list comprehension and list.count() to create a list containing only the unique values.

def filter_non_unique(lst): return [item for item in lst if lst.count(item) == 1]

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

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Groups the elements of a list based on the given function.

Use list() in combination with map() and fn to map the values of the list to the keys of an object. Use list comprehension to map each element to the appropriate key.

def group_by(lst, fn): groups = {} for key in list(map(fn,lst)): groups[key] = [item for item in lst if fn(item) == key] return groups

import math group_by([6.1, 4.2, 6.3], math.floor); # {4: [4.2], 6: [6.1, 6.3]} group_by(['one', 'two', 'three'], 'length'); # {3: ['one', 'two'], 5: ['three']}

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Returns True if there are duplicate values in a flast list, False otherwise.

Use set() on the given list to remove duplicates, compare its length with the length of the list.

def has_duplicates(lst): return len(lst) != len(set(lst))

x = [1,2,3,4,5,5] y = [1,2,3,4,5] has_duplicates(x) # True has_duplicates(y) # False

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Returns the head of a list.

use lst[0] to return the first element of the passed list.

def head(lst): return lst[0]

head([1, 2, 3]); # 1

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Returns all the elements of a list except the last one.

Use lst[0:-1] to return all but the last element of the list.

def initial(lst): return lst[0:-1]

initial([1, 2, 3]); # [1,2]

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Initializes a 2D list of given width and height and value.

Use list comprehension and range() to generate h rows where each is a list with length h, initialized with val. If val is not provided, default to None.

Explain briefly how the snippet works.

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

initialize_2d_list(2, 2, 0) # [[0,0], [0,0]]

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Initializes a list containing the numbers in the specified range where start and end are inclusive with their common difference step.

Use list and range() to generate a list of the appropriate length, filled with the desired values in the given range. Omit start to use the default value of 0. Omit step to use the default value of 1.

def initialize_list_with_range(end, start = 0, step = 1): return list(range(start, end + 1, step))

initialize_list_with_range(5) # [0, 1, 2, 3, 4, 5] initialize_list_with_range(7,3) # [3, 4, 5, 6, 7] initialize_list_with_range(9,0,2) # [0, 2, 4, 6, 8]

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Initializes and fills a list with the specified value.

Use list comprehension and range() to generate a list of length equal to n, filled with the desired values. Omit val to use the default value of 0.

def initialize_list_with_values(n, val = 0): return [val for x in range(n)]

initialize_list_with_values(5, 2) # [2, 2, 2, 2, 2]

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Returns a list of elements that exist in both lists.

Create a set from b, then use list comprehension on a to only keep values contained in both lists.

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

intersection([1, 2, 3], [4, 3, 2]) # [2, 3]

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Returns a list of elements that exist in both lists, after applying the provided function to each list element of both.

Create a set by applying fn to each element in b, then use list comprehension in combination with fn on a to only keep values contained in both lists.

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

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

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Returns the last element in a list.

use lst[-1] to return the last element of the passed list.

def last(lst): return lst[-1]

last([1, 2, 3]) # 3

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Takes any number of iterable objects or objects with a length property and returns the longest one. If multiple objects have the same length, the first one will be returned.

Use max() with len as the key to return the item with the greatest length.

def longest_item(*args): return max(args, key = len)

longest_item('this', 'is', 'a', 'testcase') # 'testcase' longest_item([1, 2, 3], [1, 2], [1, 2, 3, 4, 5]) # [1, 2, 3, 4, 5] longest_item([1, 2, 3], 'foobar') # 'foobar'

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Returns the n maximum elements from the provided list. If n is greater than or equal to the provided list's length, then return the original list (sorted in descending order).

Use sorted() to sort the list, [:n] to get the specified number of elements. Omit the second argument, n, to get a one-element list.

def max_n(lst, n=1): return sorted(lst, reverse=True)[:n]

max_n([1, 2, 3]) # [3] max_n([1, 2, 3], 2) # [3,2]

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Returns the n minimum elements from the provided list. If n is greater than or equal to the provided list's length, then return the original list (sorted in ascending order).

Use sorted() to sort the list, [:n]to get the specified number of elements. Omit the second argument,n`, to get a one-element list.

def min_n(lst, n=1): return sorted(lst, reverse=False)[:n]

min_n([1, 2, 3]) # [1] min_n([1, 2, 3], 2) # [1,2]

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Returns False if the provided function returns True for at least one element in the list, True otherwise.

Iterate over the elements of the list to test if every element in the list returns False based on fn. Omit the seconds argument, fn, to check if all elements are False.

def none(lst, fn=lambda x: not not x): for el in lst: if fn(el): return False return True

none([0, 1, 2, 0], lambda x: x >= 2 ) # False none([0, 0, 0]) # True

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Moves the specified amount of elements to the end of the list.

Use lst[offset:] and lst[:offset] to get the two slices of the list and combine them before returning.

Explain briefly how the snippet works.

def offset(lst, offset): return lst[offset:] + lst[:offset]

offset([1, 2, 3, 4, 5], 2) # [3, 4, 5, 1, 2] offset([1, 2, 3, 4, 5], -2) # [4, 5, 1, 2, 3]

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Returns a random element from an array.

Use randint() to generate a random number that corresponds to an index in the list, return the element at that index.

from random import randint def sample(lst): return lst[randint(0, len(lst) - 1)]

sample([3, 7, 9, 11]) # 9

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Randomizes the order of the values of an list, returning a new list.

Uses the Fisher-Yates algorithm to reorder the elements of the list.

from copy import deepcopy from random import randint def shuffle(lst): temp_lst = deepcopy(lst) m = len(temp_lst) while (m): m -= 1 i = randint(0, m) temp_lst[m], temp_lst[i] = temp_lst[i], temp_lst[m] return temp_lst

foo = [1,2,3] shuffle(foo) # [2,3,1] , foo = [1,2,3]

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Returns a list of elements that exist in both lists.

Use list comprehension on a to only keep values contained in both lists.

def similarity(a, b): return [item for item in a if item in b]

similarity([1, 2, 3], [1, 2, 4]) # [1, 2]

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Returns True if the provided function returns True for at least one element in the list, False otherwise.

Iterate over the elements of the list to test if every element in the list returns True based on fn. Omit the seconds argument, fn, to check if all elements are True.

def some(lst, fn=lambda x: not not x): for el in lst: if fn(el): return True return False

some([0, 1, 2, 0], lambda x: x >= 2 ) # True some([0, 0, 1, 0]) # True

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Flattens a list, by spreading its elements into a new list.

Loop over elements, use list.extend() if the element is a list, list.append() otherwise.

def spread(arg): ret = [] for i in arg: if isinstance(i, list): ret.extend(i) else: ret.append(i) return ret

spread([1,2,3,[4,5,6],[7],8,9]) # [1,2,3,4,5,6,7,8,9]

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Returns the symmetric difference between two iterables, without filtering out duplicate values.

Create a set from each list, then use list comprehension on each one to only keep values not contained in the previously created set of the other.

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]

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

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Returns the symmetric difference between two lists, after applying the provided function to each list element of both.

Create a set by applying fn to each element in every list, then use list comprehension in combination with fn on each one to only keep values not contained in the previously created set of the other.

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

from math import floor symmetric_difference_by([2.1, 1.2], [2.3, 3.4],floor) # [1.2, 3.4]

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Returns all elements in a list except for the first one.

Return lst[1:] if the list's length is more than 1, otherwise, return the whole list.

def tail(lst): return lst[1:] if len(lst) > 1 else lst

tail([1, 2, 3]); # [2,3] tail([1]); # [1]

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Returns every element that exists in any of the two lists once.

Create a set with all values of a and b and convert to a list.

def union(a,b): return list(set(a + b))

union([1, 2, 3], [4, 3, 2]) # [1,2,3,4]

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Returns every element that exists in any of the two lists once, after applying the provided function to each element of both.

Create a set by applying fn to each element in a, then use list comprehension in combination with fn on b to only keep values not contained in the previously created set, _a. Finally, create a set from the previous result and a and transform it into a list

def union_by(a,b,fn): _a = set(map(fn, a)) return list(set(a + [item for item in b if fn(item) not in _a]))

from math import floor union_by([2.1], [1.2, 2.3], floor) # [2.1, 1.2]

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Returns the unique elements in a given list.

Create a set from the list to discard duplicated values, then return a list from it.

def unique_elements(li): return list(set(li))

unique_elements([1, 2, 2, 3, 4, 3]) # [1, 2, 3, 4]

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Creates a list of elements, grouped based on the position in the original lists.

Use max combined with list comprehension to get the length of the longest list in the arguments. Loop for max_length times grouping elements. If lengths of lists vary, use fill_value (defaults to None).

def zip(*args, fillvalue=None): max_length = max([len(lst) for lst in args]) result = [] for i in range(max_length): result.append([ args[k][i] if i < len(args[k]) else fillvalue for k in range(len(args)) ]) return result

zip(['a', 'b'], [1, 2], [True, False]) # [['a', 1, True], ['b', 2, False]] zip(['a'], [1, 2], [True, False]) # [['a', 1, True], [None, 2, False]] zip(['a'], [1, 2], [True, False], fill_value = '_') # [['a', 1, True], ['_', 2, False]]

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Returns the average of two or more numbers.

Use sum() to sum all of the args provided, divide by len(args).

def average(*args): return sum(args, 0.0) / len(args)

average(*[1, 2, 3]) # 2.0 average(1, 2, 3) # 2.0

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Returns the average of a list, after mapping each element to a value using the provided function.

Use map() to map each element to the value returned by fn. Use sum() to sum all of the mapped values, divide by len(lst).

def average_by(lst, fn=lambda x: x): return sum(map(fn, lst), 0.0) / len(lst)

average_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda x: x['n']) # 5.0

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Clamps num within the inclusive range specified by the boundary values a and b.

If num falls within the range, return num. Otherwise, return the nearest number in the range.

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

clamp_number(2, 3, 5) # 3 clamp_number(1, -1, -5) # -1

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Converts a number to an array of digits.

Use map() combined with int on the string representation of n and return a list from the result.

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

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

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Calculates the factorial of a number.

Use recursion. If num is less than or equal to 1, return 1. Otherwise, return the product of num and the factorial of num - 1. Throws an exception if num is a negative or a floating point number.

def factorial(num): if not ((num >= 0) & (num % 1 == 0)): raise Exception( f"Number( {num} ) can't be floating point or negative ") return 1 if num == 0 else num * factorial(num - 1)

factorial(6) # 720

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Generates an array, containing the Fibonacci sequence, up until the nth term.

Starting with 0 and 1, use list.apoend() to add the sum of the last two numbers of the list to the end of the list, until the length of the list reaches n. If nis less or equal to0, return a list containing 0`.

def fibonacci(n): if n <= 0: return [0] sequence = [0, 1] while len(sequence) <= n: next_value = sequence[len(sequence) - 1] + sequence[len(sequence) - 2] sequence.append(next_value) return sequence

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

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Calculates the greatest common divisor of a list of numbers.

Use reduce() and math.gcd over the given list.

from functools import reduce import math def gcd(numbers): return reduce(math.gcd, numbers)

gcd([8,36,28]) # 4

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Checks if the given number falls within the given range.

Use arithmetic comparison to check if the given number is in the specified range. If the second parameter, end, is not specified, the range is considered to be from 0 to start.

def in_range(n, start, end = 0): if (start > end): end, start = start, end return start <= n <= end

in_range(3, 2, 5); # True in_range(3, 4); # True in_range(2, 3, 5); # False in_range(3, 2); # False

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Checks if the first numeric argument is divisible by the second one.

Use the modulo operator (%) to check if the remainder is equal to 0.

def is_divisible(dividend, divisor): return dividend % divisor == 0

is_divisible(6, 3) # True

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Returns True if the given number is even, False otherwise.

Checks whether a number is odd or even using the modulo (%) operator. Returns True if the number is even, False if the number is odd.

def is_even(num): return num % 2 == 0

is_even(3) # False

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Returns True if the given number is odd, False otherwise.

Checks whether a number is even or odd using the modulo (%) operator. Returns True if the number is odd, False if the number is even.

def is_odd(num): return num % 2 != 0

is_odd(3) # True

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Returns the least common multiple of two or more numbers.

Define a function, spread, that uses either list.extend() or list.append() on each element in a list to flatten it. Use math.gcd() and lcm(x,y) = x * y / gcd(x,y) to determine the least common multiple.

from functools import reduce import math def spread(arg): ret = [] for i in arg: if isinstance(i, list): ret.extend(i) else: ret.append(i) return ret def lcm(*args): numbers = [] numbers.extend(spread(list(args))) def _lcm(x, y): return int(x * y / math.gcd(x, y)) return reduce((lambda x, y: _lcm(x, y)), numbers)

lcm(12, 7) # 84 lcm([1, 3, 4], 5) # 60

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Returns the maximum value of a list, after mapping each element to a value using the provided function.

Use map() with fn to map each element to a value using the provided function, convert to a list and use max() to return the maximum value.

def max_by(lst, fn): return max(list(map(fn,lst)))

max_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda v : v['n']) # 8

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Returns the minimum value of a list, after mapping each element to a value using the provided function.

Use map() with fn to map each element to a value using the provided function, convert to a list and use min() to return the minimum value.

def min_by(lst, fn): return min(list(map(fn,lst)))

min_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda v : v['n']) # 2

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Converts an angle from radians to degrees.

Use math.pi and the radian to degree formula to convert the angle from radians to degrees.

import math def rads_to_degrees(rad): return (rad * 180.0) / math.pi

import math rads_to_degrees(math.pi / 2) # 90.0

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Returns the sum of a list, after mapping each element to a value using the provided function.

Use map() with fn to map each element to a value using the provided function, convert to a list and use sum() to return the sum of the values.

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

sum_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda v : v['n']) # 20

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Returns a flat list of all the keys in a flat dictionary.

Use dict.keys() to return the keys in the given dictionary. Return a list() of the previous result.

def keys_only(flat_dict): return list(flat_dict.keys())

ages = { "Peter": 10, "Isabel": 11, "Anna": 9, } keys_only(ages) # ['Peter', 'Isabel', 'Anna']

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Creates an object with the same keys as the provided object and values generated by running the provided function for each value.

Use dict.keys() to iterate over the object's keys, assigning the values produced by fn to each key of a new object.

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

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

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Returns a flat list of all the values in a flat dictionary.

Use dict.values() to return the values in the given dictionary. Return a list() of the previous result.

def values_only(dict): return list(flat_dict.values())

ages = { "Peter": 10, "Isabel": 11, "Anna": 9, } values_only(ages) # [10, 11, 9]

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Returns the length of a string in bytes.

Use string.encode('utf-8') to encode the given string and return its length.

def byte_size(string): return len(string.encode('utf-8'))

byte_size('😀') # 4 byte_size('Hello World') # 11

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Converts a string to camelcase.

Break the string into words and combine them capitalizing the first letter of each word, using a regexp, title() and lower.

import re def camel(s): s = re.sub(r"(\s|_|-)+", " ", s).title().replace(" ", "") return s[0].lower() + s[1:]

camel('some_database_field_name'); # 'someDatabaseFieldName' camel('Some label that needs to be camelized'); # 'someLabelThatNeedsToBeCamelized' camel('some-javascript-property'); # 'someJavascriptProperty' camel('some-mixed_string with spaces_underscores-and-hyphens'); # 'someMixedStringWithSpacesUnderscoresAndHyphens'

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Capitalizes the first letter of a string.

Capitalize the first letter of the string and then add it with rest of the string. Omit the lower_rest parameter to keep the rest of the string intact, or set it to True to convert to lowercase.

def capitalize(string, lower_rest=False): return string[:1].upper() + (string[1:].lower() if lower_rest else string[1:])

capitalize('fooBar') # 'FooBar' capitalize('fooBar', True) # 'Foobar'

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Capitalizes the first letter of every word in a string.

Use string.title() to capitalize first letter of every word in the string.

def capitalize_every_word(string): return string.title()

capitalize_every_word('hello world!') # 'Hello World!'

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Decapitalizes the first letter of a string.

Decapitalize the first letter of the string and then add it with rest of the string. Omit the upper_rest parameter to keep the rest of the string intact, or set it to True to convert to uppercase.

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

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

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Checks if a string is an anagram of another string (case-insensitive, ignores spaces, punctuation and special characters).

Use str.replace() to remove spaces from both strings. Compare the lengths of the two strings, return False if they are not equal. Use sorted() on both strings and compare the results.

def is_anagram(str1, str2): _str1, _str2 = str1.replace(" ", ""), str2.replace(" ", "") if len(_str1) != len(_str2): return False else: return sorted(_str1.lower()) == sorted(_str2.lower())

is_anagram("anagram", "Nag a ram") # True

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Checks if a string is lower case.

Convert the given string to lower case, using str.lower() and compare it to the original.

def is_lower_case(string): return string == string.lower()

is_lower_case('abc') # True is_lower_case('a3@$') # True is_lower_case('Ab4') # False

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Checks if a string is upper case.

Convert the given string to upper case, using str.upper() and compare it to the original.

def is_upper_case(string): return string == string.upper()

is_upper_case('ABC') # True is_upper_case('a3@$') # False is_upper_case('aB4') # False

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Converts a string to kebab case.

Break the string into words and combine them adding - as a separator, using a regexp.

import re def kebab(str): return re.sub(r"(\s|_|-)+","-", re.sub(r"[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+", lambda mo: mo.group(0).lower(),str) )

kebab('camelCase'); # 'camel-case' kebab('some text'); # 'some-text' kebab('some-mixed_string With spaces_underscores-and-hyphens'); # 'some-mixed-string-with-spaces-underscores-and-hyphens' kebab('AllThe-small Things'); # "all-the-small-things"

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Returns True if the given string is a palindrome, False otherwise.

Use str.lower() and re.sub() to convert to lowercase and remove non-alphanumeric characters from the given string. Then, compare the new string with its reverse.

from re import sub def palindrome(string): s = sub('[\W_]', '', string.lower()) return s == s[::-1]

palindrome('taco cat') # True

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Converts a string to snake case.

Break the string into words and combine them adding _-_ as a separator, using a regexp.

import re def snake(str): return re.sub(r"(\s|_|-)+","-", re.sub(r"[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+", lambda mo: mo.group(0).lower(),str) )

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_smal_things"

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Splits a multiline string into a list of lines.

Use str.split() and '\n' to match line breaks and create a list.

def split_lines(str): str.split('\n')

split_lines('This\nis a\nmultiline\nstring.\n') # 'This\nis a\nmultiline\nstring.\n'

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Casts the provided value as an array if it's not one.

Use isinstance() to check if the given value is a list and return it as-is or encapsulated in a list accordingly.

def cast_list(val): return val if isinstance(val, list) else [val]

cast_list('foo'); # ['foo'] cast_list([1]); # [1]

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Angelos Chalaris	Stefan Feješ	Rohit Tanwar

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