Built-in Functions

Python provides a rich set of built-in functions that are always available for use. These functions are part of the Python Standard Library and perform a variety of tasks, such as data type conversion, mathematical operations, input/output operations, and more. Here is an overview of some of the most commonly used built-in functions in Python:

Common Built-in Functions

Data Type Conversion Functions

int(): Converts a value to an integer.

num = int("10")  # Output: 10

float(): Converts a value to a floating-point number.

num = float("10.5") # Output: 10.5

str(): Converts a value to a string.

text = str(10) # Output: '10'

bool(): Converts a value to a boolean.

flag = bool(1) # Output: True

list(): Converts an iterable (e.g., tuple, string) to a list.

my_list = list("hello") # Output: ['h', 'e', 'l', 'l', 'o']

tuple(): Converts an iterable to a tuple.

my_tuple = tuple([1, 2, 3]) # Output: (1, 2, 3)

dict(): Creates a dictionary.

my_dict = dict([('a', 1), ('b', 2)])  # Output: {'a': 1, 'b': 2}

Mathematical Functions

abs(): Returns the absolute value of a number.

result = abs(-5)  # Output: 5

print(result)

round(): Rounds a number to a specified number of decimal places.

result = round(5.678, 2) # Output: 5.68

max(): Returns the largest item in an iterable or the largest of two or more arguments.

result = max(1, 2, 3) # Output: 3

min(): Returns the smallest item in an iterable or the smallest of two or more arguments.

result = min(1, 2, 3) # Output: 1

sum(): Sums the items of an iterable.

result = sum([1, 2, 3]) # Output: 6

Sequence Functions

len(): Returns the length of an object.

result = len("hello")  # Output: 5

range(): Generates a sequence of numbers.

numbers = list(range(1, 5)) # Output: [1, 2, 3, 4]

enumerate(): Adds a counter to an iterable and returns it as an enumerate object.

for index, value in enumerate(['a', 'b', 'c']): print(index, value) # Output: # 0 a # 1 b # 2 c

zip(): Aggregates elements from two or more iterables.

names = ['Alice', 'Bob'] scores = [85, 90] combined = list(zip(names, scores)) # Output: [('Alice', 85), ('Bob', 90)]

Input/Output Functions

print(): Prints the specified message to the console or other standard output device.

print("Hello, world!")  # Output: Hello, world!

input(): Reads a line from input, converts it to a string.

name = input("Enter your name: ") print(f"Hello, {name}!")

Object and Class Functions

type(): Returns the type of an object

result = type(123) # Output: <class 'int'>

isinstance(): Checks if an object is an instance of a class or a tuple of classes.

result = isinstance(123, int) # Output: True

dir(): Returns a list of the specified object's attributes and methods.

attributes = dir([]) # Output: ['__add__', '__class__', ..., 'append', 'clear', ...]

id(): Returns the identity of an object.

obj = "hello" obj_id = id(obj) # Output: 140248162356656 (the actual number will vary)

Other Useful Functions

open(): Opens a file and returns a file object.

file = open("example.txt", "r")

content = file.read()

file.close()

sorted(): Returns a new sorted list from the elements of any iterable.

numbers = [3, 1, 4, 1, 5] sorted_numbers = sorted(numbers) # Output: [1, 1, 3, 4, 5]

reversed(): Returns a reverse iterator.

reversed_list = list(reversed([1, 2, 3])) # Output: [3, 2, 1]

any(): Returns True if any element of the iterable is true.

result = any([0, 1, 2]) # Output: True

all(): Returns True if all elements of the iterable are true.

result = all([1, 2, 3]) # Output: True

eval(): Evaluates a Python expression from a string-based input.

result = eval("2 + 2") # Output: 4

exec(): Executes a dynamic Python code block.

code = "for i in range(3): print(i)" exec(code) # Output: # 0 # 1 # 2

Python's built-in functions provide a powerful toolkit for performing a wide range of tasks efficiently. Familiarity with these functions can greatly enhance your ability to write concise and readable Python code. For a full list of Python's built-in functions, you can refer to the official Python documentation.