Python Built‑in Functions for Data Type Casting

Python provides several built‑in functions such as int() , float() , str() , bool() , list() , tuple() , set() and dict() to explicitly cast objects between data types.

int() and float()

Convert strings to numbers:

num_str = "42"
num = int(num_str)
print(num)  # 42

Convert strings to floating‑point numbers:

pi_str = "3.14159"
pi = float(pi_str)
print(pi)  # 3.14159

Convert booleans and floats to integers (True → 1, False → 0, truncates decimals):

is_true = True
num = int(is_true)
print(num)  # 1

pi = 3.14159
num = int(pi)
print(num)  # 3

Convert integers to floats:

num = 42
pi = float(num)
print(pi)  # 42.0

str()

Convert various objects to their string representation:

num = 42
num_str = str(num)
print(num_str)  # "42"

pi = 3.14159
pi_str = str(pi)
print(pi_str)  # "3.14159"

is_true = True
is_true_str = str(is_true)
print(is_true_str)  # "True"

my_list = [1, 2, 3]
list_str = str(my_list)
print(list_str)  # "[1, 2, 3]"

my_dict = {'a': 1, 'b': 2, 'c': 3}
dict_str = str(my_dict)
print(dict_str)  # "{'a': 1, 'b': 2, 'c': 3}"

bool()

Convert values to boolean based on truthiness:

num = 42
is_true = bool(num)
print(is_true)  # True

pi = 3.14159
is_true = bool(pi)
print(is_true)  # True

empty_str = ""
is_true = bool(empty_str)
print(is_true)  # False

nonempty_str = "Hello"
is_true = bool(nonempty_str)
print(is_true)  # True

empty_list = []
is_true = bool(empty_list)
print(is_true)  # False

list()

Convert iterables to lists:

text = "Hello, World!"
char_list = list(text)
print(char_list)  # ['H', 'e', 'l', 'l', 'o', ',', ' ', 'W', 'o', 'r', 'l', 'd', '!']

tuple_data = (1, 2, 3, 4, 5)
list_data = list(tuple_data)
print(list_data)  # [1, 2, 3, 4, 5]

set_data = {1, 2, 3, 4, 5}
list_data = list(set_data)
print(list_data)  # order may vary

sentence = "I love Python"
word_list = sentence.split()
print(word_list)  # ['I', 'love', 'Python']

numbers = "1 2 3 4 5"
number_list = [int(num) for num in numbers.split()]
print(number_list)  # [1, 2, 3, 4, 5]

tuple()

Convert iterables to tuples:

list_data = [1, 2, 3, 4, 5]
tuple_data = tuple(list_data)
print(tuple_data)  # (1, 2, 3, 4, 5)

text = "Hello, World!"
char_tuple = tuple(text)
print(char_tuple)  # ('H', 'e', 'l', 'l', 'o', ',', ' ', 'W', 'o', 'r', 'l', 'd', '!')

set_data = {1, 2, 3, 4, 5}
tuple_data = tuple(set_data)
print(tuple_data)  # order may vary

sentence = "I love Python"
word_tuple = tuple(sentence.split())
print(word_tuple)  # ('I', 'love', 'Python')

numbers = "1 2 3 4 5"
number_tuple = tuple(int(num) for num in numbers.split())
print(number_tuple)  # (1, 2, 3, 4, 5)

set()

Convert iterables to sets (unique, unordered):

list_data = [1, 2, 3, 4, 5]
set_data = set(list_data)
print(set_data)  # {1, 2, 3, 4, 5}

tuple_data = (1, 2, 3, 4, 5)
set_data = set(tuple_data)
print(set_data)  # {1, 2, 3, 4, 5}

text = "Hello, World!"
set_data = set(text)
print(set_data)  # unique characters

sentence = "I love Python"
word_set = set(sentence.split())
print(word_set)  # {'I', 'love', 'Python'}

list_data = [1, 2, 3, 3, 4, 4, 5, 5]
unique_set = set(list_data)
print(unique_set)  # {1, 2, 3, 4, 5}

dict()

Convert iterable key‑value pairs to dictionaries:

list_data = [('a', 1), ('b', 2), ('c', 3)]
dict_data = dict(list_data)
print(dict_data)  # {'a': 1, 'b': 2, 'c': 3}

tuple_data = (('a', 1), ('b', 2), ('c', 3))
dict_data = dict(tuple_data)
print(dict_data)  # {'a': 1, 'b': 2, 'c': 3}

keys = ['a', 'b', 'c']
values = [1, 2, 3]
dict_data = dict(zip(keys, values))
print(dict_data)  # {'a': 1, 'b': 2, 'c': 3}

set_data = {('a', 1), ('b', 2), ('c', 3)}
dict_data = dict(set_data)
print(dict_data)  # {'a': 1, 'b': 2, 'c': 3}

keys = ['a', 'b', 'c']
values = [1, 2, 3]
dict_data = {key: value for key, value in zip(keys, values)}
print(dict_data)  # {'a': 1, 'b': 2, 'c': 3}