Python is a popular language used for a wide range of programming applications. One of the benefits of Python is the vast array of built-in functions that simplify programming and make it easier to write efficient code. In this article, we’ll explore some of the most commonly used built-in functions in Python, and provide examples of how they can be used.
What are Built-in Functions?
Built-in functions are pre-defined functions that are included in the Python language. They are designed to perform specific tasks, such as manipulating strings, performing mathematical operations, or handling files. Unlike user-defined functions, built-in functions do not require any explicit definition or import statements. They are always available to the programmer.
Python has many built-in functions that can be used to perform a variety of tasks. In this guide, we’ll take a look at some of the most commonly used built-in functions in Python, and provide examples of how they can be used.
Examples of Built-in Functions
Mathematical Functions
Python includes a number of built-in mathematical functions that can be used to perform basic arithmetic operations. Some of the most commonly used mathematical functions in Python include:
abs() – returns the absolute value of a number
pow() – raises a number to a specified power
round() – rounds a number to a specified number of decimal places
max() – returns the largest value in a list or tuple
min() – returns the smallest value in a list or tuple
print(abs(-10)) # Output: 10
print(pow(2, 3)) # Output: 8
print(round(3.14159, 2)) # Output: 3.14
print(max(2, 5, 8, 1)) # Output: 8
print(min(2, 5, 8, 1)) # Output: 1
Here are a few more examples of mathematical built-in functions in Python:
divmod() - returns the quotient and remainder when one number is divided by another
sum() - returns the sum of all the elements in a list or tuple
round() - rounds a number to the nearest integer
floor() - returns the largest integer less than or equal to a given number
ceil() - returns the smallest integer greater than or equal to a given number
print(divmod(10, 3)) # Output: (3, 1)
my_list = [1, 2, 3, 4, 5]
print(sum(my_list)) # Output: 15
print(round(3.7)) # Output: 4
import math
print(math.floor(3.9)) # Output: 3
print(math.ceil(3.1)) # Output: 4
String Functions
Python also includes a number of built-in functions for manipulating strings. Strings are a fundamental data type in Python, and they are used extensively in programming. Some of the most commonly used string functions in Python include:
len() – returns the length of a string
capitalize() – capitalizes the first letter of a string
replace() – replaces a specified substring with another substring
split() – splits a string into a list of substrings based on a specified delimiter
join() – joins a list of strings into a single string using a specified delimiter
text = "hello world"
print(len(text)) # Output: 11
print(text.capitalize()) # Output: Hello world
print(text.replace("world", "Python")) # Output: hello Python
print(text.split(" ")) # Output: ['hello', 'world']
words = ["hello", "world"]
print(" ".join(words)) # Output: hello world
Here are a few more examples of string built-in functions in Python:
lower() – returns a string in all lowercase letters
upper() – returns a string in all uppercase letters
strip() – removes leading and trailing whitespace from a string
startswith() – returns True if a string starts with a specified substring
endswith() – returns True if a string ends with a specified substring
text = " Hello, World! "
print(text.lower()) # Output: " hello, world! "
print(text.upper()) # Output: " HELLO, WORLD! "
print(text.strip()) # Output: "Hello, World!"
print(text.startswith("Hello")) # Output: False
print(text.endswith("!")) # Output: True
List Functions
Python includes a number of built-in functions for manipulating lists. Lists are another fundamental data type in Python, and they are used extensively in programming. Some of the most commonly used list functions in Python include:
append() – adds an element to the end of a list
remove() – removes the first occurrence of a specified element from a list
sort() – sorts the elements of a list
reverse() – reverses the order of the elements in a list
count() – returns the number of times a specified element appears in a list
fruits = ["apple", "banana", "cherry"]
fruits.append("orange")
print(fruits) # Output: ['apple', 'banana', 'cherry', 'orange']
fruits.remove("banana")
print(fruits) # Output: ['apple', 'cherry', 'orange']
fruits.sort()
print(fruits) # Output: ['apple', 'cherry', 'orange']
fruits.reverse()
print(fruits) # Output: ['orange', 'cherry', 'apple']
print(fruits.count("cherry")) # Output: 1
Here are a few more examples of list built-in functions in Python:
extend() – adds the elements of one list to the end of another list
index() – returns the index of the first occurrence of a specified element in a list
insert() – inserts an element at a specified index in a list
pop() – removes and returns the element at a specified index in a list
clear() – removes all the elements from a list
my_list = [1, 2, 3]
my_list.extend([4, 5])
print(my_list) # Output: [1, 2, 3, 4, 5]
print(my_list.index(3)) # Output: 2
my_list.insert(1, 6)
print(my_list) # Output: [1, 6, 2, 3, 4, 5]
removed_element = my_list.pop(2)
print(my_list) # Output: [1, 6, 3, 4, 5]
print(removed_element) # Output: 2
my_list.clear()
print(my_list) # Output: []
Dictionary Functions
Python dictionaries are another fundamental data type in Python, and they are used extensively in programming. Dictionaries are a collection of key-value pairs, and they can be used to store and retrieve data efficiently. Some of the most commonly used dictionary functions in Python include:
keys() – returns a list of all the keys in a dictionary
values() – returns a list of all the values in a dictionary
items() – returns a list of all the key-value pairs in a dictionary
get() – returns the value associated with a specified key
pop() – removes the key-value pair associated with a specified key
person = {"name": "John", "age": 25, "country": "USA"}
print(person.keys()) # Output: dict_keys(['name', 'age', 'country'])
print(person.values()) # Output: dict_values(['John', 25, 'USA'])
print(person.items()) # Output: dict_items([('name', 'John'), ('age', 25), ('country', 'USA')])
print(person.get("name")) # Output: John
person.pop("age")
print(person) # Output: {'name': 'John', 'country': 'USA'}
Here are a few more examples of built-in dictionary functions in Python:
update() - updates the keys and values in a dictionary with another dictionary or key-value pairs
clear() - removes all the key-value pairs from a dictionary
copy() - returns a shallow copy of a dictionary
popitem() - removes and returns a random key-value pair from a dictionary
person = {"name": "John", "age": 25, "country": "USA"}
person2 = {"name": "Jane", "city": "New York"}
person.update(person2)
print(person) # Output: {'name': 'Jane', 'age': 25, 'country': 'USA', 'city': 'New York'}
person.clear()
print(person) # Output: {}
person = person2.copy()
print(person) # Output: {'name': 'Jane', 'city': 'New York'}
person.popitem()
print(person) # Output: {'name': 'Jane'}
File Handling Functions
Python provides built-in functions for handling files. These functions can be used to open, read, write, and close files in Python. Some of the most commonly used file handling functions in Python include:
open() – opens a file and returns a file object
read() – reads the contents of a file
write() – writes data to a file
close() – closes a file object
# Open a file
file = open("example.txt", "w")
# Write data to the file
file.write("Hello, world!")
# Close the file
file.close()
# Open the file again and read its contents
file = open("example.txt", "r")
print(file.read()) # Output: Hello, world!
file.close()
File Handling Functions (continued)
Here are a few more examples of built-in file handling functions in Python:
readline() – reads a single line from a file
readlines() – reads all the lines from a file and returns them as a list
writelines() – writes a list of strings to a file
seek() – sets the current position in a file
tell() – returns the current position in a file
# Open a file
file = open("example.txt", "r")
# Read a single line from the file
line = file.readline()
print(line) # Output: Hello, world!
# Read all the lines from the file and return them as a list
lines = file.readlines()
print(lines) # Output: ['Hello, world!\\\\n', 'This is a test file.\\\\n']
# Close the file
file.close()
# Open the file again and write a list of strings to it
file = open("example.txt", "w")
file.writelines(["This is line 1.\\\\n", "This is line 2.\\\\n", "This is line 3.\\\\n"])
file.close()
# Open the file again and read its contents
file = open("example.txt", "r")
print(file.read()) # Output: This is line 1.\\\\nThis is line 2.\\\\nThis is line 3.\\\\n
file.close()
# Open the file again and set the current position to the beginning of the file
file = open("example.txt", "r")
file.seek(0)
# Read the first two characters from the file
print(file.read(2)) # Output: Th
# Get the current position in the file
print(file.tell()) # Output: 2
# Close the file
file.close()
Type Conversion Functions
Python provides built-in functions for converting data from one type to another. These functions can be used to convert between different data types, such as integers, floats, strings, and lists. Some of the most commonly used type conversion functions in Python include:
int() – converts a string or float to an integer
float() – converts a string or integer to a float
str() – converts any data type to a string
list() – converts any iterable to a list
print(int("42")) # Output: 42
print(float("3.14")) # Output: 3.14
print(str(42)) # Output: "42"
print(list("hello")) # Output: ['h', 'e', 'l', 'l', 'o']
Here are a few more examples of built-in type conversion functions in Python:
bool() – converts a value to a Boolean (True or False) value
tuple() – converts any iterable to a tuple
set() – converts any iterable to a set
dict() – converts a sequence of key-value pairs to a dictionary
print(bool(0)) # Output: False
print(bool(1)) # Output: True
print(tuple("hello")) # Output: ('h', 'e', 'l', 'l', 'o')
print(set([1, 2, 3, 2, 1])) # Output: {1, 2, 3}
print(dict([("name", "John"), ("age", 25), ("country", "USA")])) # Output: {'name': 'John', 'age': 25, 'country': 'USA'}
Input and Output Functions
Python provides built-in functions for getting input from the user and printing output to the console. These functions can be used to interact with the user and display information in the console. Some of the most commonly used input and output functions in Python include:
input() – gets input from the user
print() – prints output to the console
name = input("What is your name? ")
print("Hello, " + name + "!")
Conclusion
In this guide, we’ve explored some of the most commonly used built-in functions in Python. These functions can simplify programming and make it easier to write efficient code. Whether you’re manipulating strings, performing mathematical operations, handling lists, working with dictionaries, handling files, or getting input from the user and printing output to the console, Python’s built-in functions can help you get the job done. By mastering these functions, you’ll be well on your way to becoming a proficient Python programmer.