Python Built-in Functions and Common Usage Guide

Python offers 68 built-in functions (as of version 3.6.2) such as print , input , abs , len , and many others that can be used directly without import.

Numeric related functions

Data types: bool , int , float , complex

Base conversion: bin() (binary), oct() (octal), hex() (hexadecimal)

<code><span>print(bin(10))   # 二进制:0b1010</span></code><code><span>print(hex(10))   # 十六进制:0xa</span></code><code><span>print(oct(10))   # 八进制:0o12</span></code>

Mathematical operations

abs() – absolute value

divmod() – quotient and remainder

round() – rounding

pow(a, b, mod=None) – exponentiation (optional modulus)

sum() , min() , max() – aggregation

<code><span>print(abs(-2))               # 2</span></code><code><span>print(divmod(20, 3))        # (6, 2)</span></code><code><span>print(round(4.51))           # 5</span></code><code><span>print(pow(10, 2, 3))        # 1</span></code><code><span>print(sum([1,2,3,4,5,6,7,8,9,10]))  # 55</span></code><code><span>print(min(5,3,9,12,7,2))   # 2</span></code><code><span>print(max(7,3,15,9,4,13))   # 15</span></code>

Sequences and collections

list() converts an iterable to a list; tuple() converts to a tuple.

reversed() returns an iterator that yields items in reverse order.

slice() creates a slice object for list slicing.

<code><span>lst = ["你好啊"]</span></code><code><span>it = reversed(lst)</span></code><code><span>print(list(it))   # ['啊', '好', '你']</span></code><code><span>lst = [1,2,3,4,5,6,7]</span></code><code><span>print(lst[1:3:1])   # [2, 3]</span></code><code><span>s = slice(1,3,1)</span></code><code><span>print(lst[s])       # [2, 3]</span></code>

String handling

str() converts a value to a string.

format() formats strings with alignment, base conversion, and scientific notation.

<code><span>print(str(123) + '456')               # 123456</span></code><code><span>print(format('hello world!', '^20')) #   hello world!   </span></code><code><span>print(format('hello world!', '<20')) # hello world!        </span></code><code><span>print(format('hello world!', '>20')) #        hello world!</span></code><code><span>print(format(11, 'b'))               # 1011</span></code><code><span>print(format(11, 'c'))               # k</span></code><code><span>print(format(123456789, 'e'))         # 1.234568e+08</span></code>

Bytes and encoding

bytes() creates a bytes object from a string.

bytearray() creates a mutable byte array.

ord() returns the Unicode code point of a character; chr() returns the character for a code point.

<code><span>bs = bytes("今天吃饭了吗", encoding="utf-8")</span></code><code><span>print(bs)   # b'\xe4\xbb\x8a\xe5\xa4\xa9\xe5\x90\x83\xe9\xa5\xad\xe4\xba\x86\xe5\x90\x97'</span></code><code><span>ret = bytearray("alex", encoding="utf-8")</span></code><code><span>print(ret[0])   # 97</span></code><code><span>print(ret)      # bytearray(b'alex')</span></code><code><span>ret[0] = 65</span></code><code><span>print(str(ret)) # bytearray(b'Alex')</span></code><code><span>print(ord('a'))   # 97</span></code><code><span>print(chr(65))    # A</span></code>

Collections utilities

len() – number of items.

sorted() – returns a new sorted list; supports key and reverse arguments.

enumerate() – yields (index, element) pairs.

all() / any() – logical aggregation over iterables.

zip() – aggregates elements from multiple iterables.

filter() – filters items using a predicate function.

map() – applies a function to each item.

<code><span>lst = [5,7,6,12,1,13,9,18,5]</span></code><code><span>print(sorted(lst))                # [1, 5, 5, 6, 7, 9, 12, 13, 18]</span></code><code><span>print(sorted(lst, reverse=True)) # [18, 13, 12, 9, 7, 6, 5, 5, 1]</span></code><code><span>def f(s): return len(s)</span></code><code><span>print(sorted(['one','two','three','four','five','six'], key=f))</span></code><code><span>print(all([1,'hello',True,9]))   # True</span></code><code><span>print(any([0,0,0,False,1,'good'])) # True</span></code><code><span>lst1 = [1,2,3,4,5,6]</span></code><code><span>lst2 = ['醉乡民谣','驴得水','放牛班的春天','美丽人生','辩护人','被嫌弃的松子的一生']</span></code><code><span>lst3 = ['美国','中国','法国','意大利','韩国','日本']</span></code><code><span>for el in zip(lst1, lst2, lst3): print(el)</span></code>

Scope utilities

locals() – dictionary of current local symbol table.

globals() – dictionary of global symbol table.

<code><span>def func():</span></code><code><span>    a = 10</span></code><code><span>    print(locals())   # {'a': 10}</span></code><code><span>    print(globals())  # {...}</span></code><span>func()</span></code>

Iterator and generator helpers

range() – generates arithmetic progressions.

iter() – returns an iterator from an iterable.

next() – fetches the next item from an iterator.

<code><span>for i in range(15, -1, -5): print(i)</span></code><code><span># 15 10 5 0</span></code><code><span>lst = [1,2,3,4,5]</span></code><code><span>it = iter(lst)</span></code><code><span>print(next(it))   # 1</span></code>

Dynamic code execution

eval() – evaluates an expression string and returns the result.

exec() – executes a block of code.

compile() – compiles source code to a code object.

<code><span>s1 = input("请输入a+b:")   # e.g., 8+9</span></code><code><span>print(eval(s1))               # 17</span></code><code><span>s2 = "for i in range(5): print(i)"</span></code><code><span>exec(s2)                     # prints 0-4</span></code><code><span>code1 = "for i in range(3): print(i)"</span></code><code><span>com = compile(code1, "", mode="exec")</span></code><code><span>exec(com)                     # 0 1 2</span></code>

Input/Output

print() – prints to stdout with optional sep and end parameters.

input() – reads a line from stdin.

<code><span>print("hello", "world", sep="*", end="@")   # hello*world@</span></code>

Memory utilities

hash() – returns the hash value of an object.

id() – returns the memory address of an object.

<code><span>s = 'alex'</span></code><code><span>print(hash(s))   # e.g., -168324845050430382</span></code><code><span>print(id(s))     # e.g., 2278345368944</span></code>

File operations

open() – opens a file and returns a file object.

<code><span>f = open('file', mode='r', encoding='utf-8')</span></code><code><span>content = f.read()</span></code><code><span>f.close()</span></code>

Module handling

__import__() – imports a module dynamically.

help() – displays the help page for an object.

callable() – checks if an object appears callable.

dir() – lists the attributes of an object.

<code><span>name = input("请输入你要导入的模块:")</span></code><code><span>__import__(name)</span></code><code><span>print(help(str))</span></code><code><span>a = 10</span></code><code><span>print(callable(a))   # False</span></code><code><span>def f(): print("hello")</span></code><code><span>print(callable(f))   # True</span></code><code><span>print(dir(tuple))</span></code>

This guide consolidates essential Python built‑in functions and utilities, providing clear explanations and ready‑to‑run code snippets for learners and developers seeking a solid foundation in Python programming.