36 Frequently Used Python Built-in Functions with Usage Scenarios and Code Examples

print() prints output, useful for debugging, logging, and displaying information. Example: print("Hello, World!")

len() returns the length or number of items of an object, such as strings, lists, tuples, or dictionaries. Example: my_list = [1, 2, 3, 4, 5] print(len(my_list)) # 输出: 5

type() returns the type of an object, useful for checking variable types. Example: x = 10 print(type(x)) # 输出:

str() converts an object to a string, e.g., numbers or lists. Example: num = 123 print(str(num)) # 输出: '123'

int() converts an object to an integer, useful for strings or floats. Example: num_str = "123" print(int(num_str)) # 输出: 123

float() converts an object to a floating‑point number. Example: num_str = "123.45" print(float(num_str)) # 输出: 123.45

bool() converts an object to a boolean value. Example: empty_list = [] print(bool(empty_list)) # 输出: False

list() converts an iterable to a list. Example: my_tuple = (1, 2, 3) print(list(my_tuple)) # 输出: [1, 2, 3]

tuple() converts an iterable to a tuple. Example: my_list = [1, 2, 3] print(tuple(my_list)) # 输出: (1, 2, 3)

dict() creates a dictionary from a sequence of key‑value pairs. Example: my_list = [('name', 'Alice'), ('age', 30)] print(dict(my_list)) # 输出: {'name': 'Alice', 'age': 30}

set() converts an iterable to a set, useful for deduplication. Example: my_list = [1, 2, 2, 3, 4, 4] print(set(my_list)) # 输出: {1, 2, 3, 4}

range() generates an integer sequence, often used in loops. Example: for i in range(5): print(i) # 输出: 0 1 2 3 4

enumerate() yields index‑value pairs while iterating. Example: my_list = ['a', 'b', 'c'] for index, value in enumerate(my_list): print(index, value) # 输出: 0 a 1 b 2 c

zip() aggregates elements from multiple iterables into tuples. Example: names = ['Alice', 'Bob', 'Charlie'] ages = [25, 30, 35] for name, age in zip(names, ages): print(name, age) # 输出: Alice 25 Bob 30 Charlie 35

map() applies a function to each item of an iterable. Example: numbers = [1, 2, 3, 4, 5] squared = map(lambda x: x**2, numbers) print(list(squared)) # 输出: [1, 4, 9, 16, 25]

filter() filters elements of an iterable based on a predicate. Example: numbers = [1, 2, 3, 4, 5] even_numbers = filter(lambda x: x % 2 == 0, numbers) print(list(even_numbers)) # 输出: [2, 4]

reduce() performs cumulative computation on an iterable (requires functools ). Example: from functools import reduce numbers = [1, 2, 3, 4, 5] product = reduce(lambda x, y: x * y, numbers) print(product) # 输出: 120

sorted() returns a sorted list from an iterable. Example: numbers = [3, 1, 4, 1, 5, 9] sorted_numbers = sorted(numbers) print(sorted_numbers) # 输出: [1, 1, 3, 4, 5, 9]

reversed() returns an iterator that accesses the given sequence in reverse order. Example: my_list = [1, 2, 3, 4, 5] reversed_list = list(reversed(my_list)) print(reversed_list) # 输出: [5, 4, 3, 2, 1]

sum() computes the total of an iterable of numbers. Example: numbers = [1, 2, 3, 4, 5] total = sum(numbers) print(total) # 输出: 15

min() returns the smallest item of an iterable. Example: numbers = [1, 2, 3, 4, 5] minimum = min(numbers) print(minimum) # 输出: 1

max() returns the largest item of an iterable. Example: numbers = [1, 2, 3, 4, 5] maximum = max(numbers) print(maximum) # 输出: 5

any() checks if any element of an iterable is true. Example: numbers = [0, 1, 2, 3, 4] has_non_zero = any(numbers) print(has_non_zero) # 输出: True

all() checks if all elements of an iterable are true. Example: numbers = [1, 2, 3, 4, 5] all_positive = all(numbers) print(all_positive) # 输出: True

abs() returns the absolute value of a number. Example: num = -10 absolute_value = abs(num) print(absolute_value) # 输出: 10

round() rounds a number to a given precision. Example: num = 3.14159 rounded_num = round(num, 2) print(rounded_num) # 输出: 3.14

pow() computes exponentiation. Example: base = 2 exponent = 3 result = pow(base, exponent) print(result) # 输出: 8

divmod() returns a tuple of (quotient, remainder). Example: a = 10 b = 3 quotient, remainder = divmod(a, b) print(quotient, remainder) # 输出: 3 1

chr() returns the character represented by an integer Unicode code point. Example: ascii_code = 65 char = chr(ascii_code) print(char) # 输出: A

ord() returns an integer representing the Unicode code point of a character. Example: char = 'A' ascii_code = ord(char) print(ascii_code) # 输出: 65

bin() returns the binary representation of an integer. Example: num = 10 binary_representation = bin(num) print(binary_representation) # 输出: 0b1010

hex() returns the hexadecimal representation of an integer. Example: num = 255 hex_representation = hex(num) print(hex_representation) # 输出: 0xff

oct() returns the octal representation of an integer. Example: num = 10 octal_representation = oct(num) print(octal_representation) # 输出: 0o12

id() returns the unique identifier of an object. Example: a = [1, 2, 3] b = a print(id(a) == id(b)) # 输出: True

input() reads a line from input. Example: name = input("请输入您的名字: ") print(f"您好，{name}!")

open() opens a file and returns a file object. Example: with open('example.txt', 'r') as file: content = file.read() print(content)

In summary, mastering these 36 high‑frequency Python built‑in functions can greatly improve coding efficiency and problem‑solving capability.