A Guided Tour of Python's Built-in Magic

Python comes with a treasure chest of “built-in” functions that are available to you at all times, without needing to import anything. Mastering these functions is a key step toward writing clean, efficient, and “Pythonic” code.

Let’s go on a guided tour of some of the most useful and powerful ones!

Iteration & Collections

These functions are your best friends when working with lists, tuples, and other iterables.

enumerate()

Adds a counter to an iterable. Instead of managing an index manually, enumerate gives you both the index and the item.

fruits = ["apple", "banana", "cherry"]
for index, fruit in enumerate(fruits):
    print(f"{index}: {fruit}")
# Output:
# 0: apple
# 1: banana
# 2: cherry

zip()

Combines multiple iterables into a single iterator of tuples. It stops when the shortest iterable is exhausted.

students = ["Alice", "Bob", "Charlie"]
scores = [85, 92, 78]
for student, score in zip(students, scores):
    print(f"{student}'s score is {score}")
# Output:
# Alice's score is 85
# Bob's score is 92
# Charlie's score is 78

map()

Applies a function to every item of an iterable and returns a map object (which you can convert to a list).

numbers = [1, 2, 3, 4]
squared = map(lambda x: x**2, numbers)
print(list(squared)) # Output: [1, 4, 9, 16]

filter()

Filters an iterable by keeping only the items that return True for a given function.

numbers = [1, 2, 3, 4, 5, 6]
evens = filter(lambda x: x % 2 == 0, numbers)
print(list(evens)) # Output: [2, 4, 6]

sorted()

Returns a new sorted list from the items in an iterable.

numbers = [3, 1, 4, 1, 5, 9, 2]
print(sorted(numbers)) # Output: [1, 1, 2, 3, 4, 5, 9]
print(sorted(numbers, reverse=True)) # Output: [9, 5, 4, 3, 2, 1, 1]

Math & Numbers

Quick and easy functions for common mathematical operations.

sum()

Calculates the sum of all items in an iterable.

numbers = [10, 20, 30]
print(sum(numbers)) # Output: 60

max() & min()

Find the largest and smallest items in an iterable.

numbers = [10, 5, 25, 15]
print(max(numbers)) # Output: 25
print(min(numbers)) # Output: 5

abs()

Returns the absolute value of a number.

print(abs(-42)) # Output: 42

round()

Rounds a number to a given precision in decimal digits.

print(round(3.14159, 2)) # Output: 3.14

Type Conversion

Functions to convert data from one type to another.

# str(), int(), float()
num_str = "123"
num_int = int(num_str) # 123 (integer)
num_float = float(num_str) # 123.0 (float)

# list(), tuple(), set(), dict()
my_tuple = (1, 2, 3)
my_list = list(my_tuple) # [1, 2, 3]

my_list_with_dupes = [1, 2, 2, 3]
my_set = set(my_list_with_dupes) # {1, 2, 3} (duplicates removed)

Object Introspection & I/O

Functions for inspecting objects and handling basic input/output.

len()

Returns the number of items in an object.

my_list = [1, 2, 3, 4]
print(len(my_list)) # Output: 4

type()

Returns the type of an object.

print(type(123)) # Output: <class 'int'>
print(type("hello")) # Output: <class 'str'>

isinstance()

Checks if an object is an instance of a class.

if isinstance("hello", str):
    print("It's a string!")

print() & input()

The most fundamental I/O functions. print() displays output to the console, and input() reads a line of text from the user.

print("Hello, world!")
name = input("What's your name? ")
print(f"Hello, {name}!")

Conclusion

This is just a glimpse into the world of Python’s built-in functions. By familiarizing yourself with them, you can solve common problems more elegantly and write code that is both more readable and more efficient. Dive in and explore!