python必背代码大全

理解和熟练掌握一门编程语言的关键部分是掌握一些基本的代码片段和常用的语法结构。

python
print("Hello, World!")

变量和数据类型

python
x = 10
y = 3.14
name = "John"
is_true = True

条件语句

python
if x > 0:
    print("x is positive")
elif x == 0:
    print("x is zero")
else:
    print("x is negative")

循环语句

python
for i in range(5):
    print(i)

while x > 0:
    print(x)
    x -= 1

数据结构

列表

python
my_list = [1, 2, 3, 4, 5]
print(my_list[2])

元组

python
my_tuple = (1, "apple", 3.14)
print(my_tuple[1])

字典

python
my_dict = {"name": "John", "age": 25, "city": "New York"}
print(my_dict["age"])

集合

python
my_set = {1, 2, 3, 4, 5}

函数

定义函数

python
def greet(name):
    return "Hello, " + name + "!"

result = greet("Alice")
print(result)

匿名函数 (lambda)

python
add = lambda x, y: x + y
print(add(3, 4))

文件操作

读取文件

python
with open("filename.txt", "r") as file:
    content = file.read()
    print(content)

写入文件

python
with open("output.txt", "w") as file:
    file.write("Hello, World!")

异常处理

Try-Except

python
try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero.")

面向对象编程 (OOP)

类和对象

python
class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def bark(self):
        print("Woof!")

my_dog = Dog("Buddy", 3)
print(my_dog.name)
my_dog.bark()

继承

python
class Cat(Dog):
    def purr(self):
        print("Meow!")

my_cat = Cat("Whiskers", 2)
my_cat.bark()
my_cat.purr()

模块和包

导入模块

python
import math
print(math.sqrt(25))

创建自定义模块

python
# mymodule.py
def greet(name):
    return "Hello, " + name + "!"

# main.py
import mymodule
print(mymodule.greet("Alice"))

使用第三方库

python
# 安装库：pip install library_name
import requests
response = requests.get("https://www.example.com")
print(response.text)

并发编程

多线程

python
import threading

def print_numbers():
    for i in range(5):
        print(i)

def print_letters():
    for letter in 'ABCDE':
        print(letter)

thread1 = threading.Thread(target=print_numbers)
thread2 = threading.Thread(target=print_letters)

thread1.start()
thread2.start()

thread1.join()
thread2.join()

多进程

python
import multiprocessing

def square_numbers(numbers, result):
    for index, num in enumerate(numbers):
        result[index] = num * num

if __name__ == "__main__":
    numbers = [1, 2, 3, 4, 5]
    result = multiprocessing.Array('i', len(numbers))

    process = multiprocessing.Process(target=square_numbers, args=(numbers, result))
    process.start()
    process.join()

    print(result[:])