Common Python Built‑in Functions: map, filter, reduce, sorted and More

map(function, iterable, ...) applies a function to each item of an iterable and returns an iterator of results. def square(x): return x ** 2 numbers = [1, 2, 3, 4, 5] squared_numbers = map(square, numbers) print(list(squared_numbers)) # [1, 4, 9, 16, 25]

filter(function, iterable) returns an iterator containing only the elements for which the function returns True. def is_even(x): return x % 2 == 0 numbers = [1, 2, 3, 4, 5, 6] even_numbers = filter(is_even, numbers) print(list(even_numbers)) # [2, 4, 6]

reduce(function, iterable[, initializer]) cumulatively applies a binary function to the items of an iterable, optionally starting with an initializer. from functools import reduce numbers = [1, 2, 3, 4, 5] sum_result = reduce(lambda x, y: x + y, numbers) print(sum_result) # 15

sorted(iterable[, key, reverse]) returns a new list containing all items from the iterable in sorted order, with optional key and reverse arguments. words = ["apple", "orange", "banana", "cherry"] sorted_words = sorted(words, key=len) print(sorted_words) # ['apple', 'cherry', 'banana', 'orange']

any(iterable) returns True if at least one element of the iterable is true, otherwise False. numbers = [0, False, "", None] has_true_value = any(numbers) print(has_true_value) # False

all(iterable) returns True only if every element of the iterable is true, otherwise False. bool_values = [True, True, True] all_true = all(bool_values) print(all_true) # True

zip(*iterables) aggregates elements from each of the iterables into tuples. names = ["Alice", "Bob", "Charlie"] ages = [25, 30, 35] name_age_pairs = zip(names, ages) print(list(name_age_pairs)) # [('Alice', 25), ('Bob', 30), ('Charlie', 35)]

enumerate(iterable[, start]) yields pairs containing a count (from start) and the corresponding value from the iterable. fruits = ["apple", "banana", "cherry"] indexed_fruits = enumerate(fruits) print(list(indexed_fruits)) # [(0, 'apple'), (1, 'banana'), (2, 'cherry')]

reversed(seq) returns an iterator that accesses the given sequence in the reverse order. numbers = [1, 2, 3, 4, 5] reversed_numbers = reversed(numbers) print(list(reversed_numbers)) # [5, 4, 3, 2, 1]

chr(i) returns the string representing a character whose Unicode code point is the integer i. code_point = 97 character = chr(code_point) print(character) # 'a'

max(iterable[, default=obj, key=func]) returns the largest item in an iterable. numbers = [1, 2, 3, 4, 5] largest_number = max(numbers) print(largest_number) # 5

min(iterable[, default=obj, key=func]) returns the smallest item in an iterable. numbers = [1, 2, 3, 4, 5] smallest_number = min(numbers) print(smallest_number) # 1

sum(iterable[, start]) returns the total of all elements in the iterable, optionally adding a start value. numbers = [1, 2, 3, 4, 5] total_sum = sum(numbers) print(total_sum) # 15

str.join(iterable) concatenates the string representations of an iterable's items using the string as a separator. words = ["apple", "banana", "cherry"] joined_words = "-".join(words) print(joined_words) # apple-banana-cherry

list(iterable) converts an iterable into a list. range_iterator = range(5) numbers_list = list(range_iterator) print(numbers_list) # [0, 1, 2, 3, 4]

tuple(iterable) converts an iterable into a tuple. numbers_list = [1, 2, 3, 4, 5] numbers_tuple = tuple(numbers_list) print(numbers_tuple) # (1, 2, 3, 4, 5)

set(iterable) creates a set from an iterable, removing duplicate elements. numbers_list = [1, 2, 3, 2, 1, 4, 5] unique_numbers_set = set(numbers_list) print(unique_numbers_set) # {1, 2, 3, 4, 5}

frozenset(iterable) creates an immutable set from an iterable, also removing duplicates. numbers_list = [1, 2, 3, 2, 1, 4, 5] unique_numbers_frozenset = frozenset(numbers_list) print(unique_numbers_frozenset) # frozenset({1, 2, 3, 4, 5})

type(obj) returns the type of the given object. number = 123 number_type = type(number) print(number_type) #

dir(obj) returns a list of the attributes and methods of the object. import os os_dir = dir(os) print(os_dir) # ['__all__', '__builtins__', '__cached__', ...]