py：python基础语法学习

下面介绍一下关于python的基础语法学习

注释

# 单行注释
print("Hello, World!")

# 多行注释。
"""这是一段多行注释"""
print("Hello, World!")

变量和数据类型

# 变量赋值
name = "Alice"
age = 30
print(name, age)  # 输出 Alice 30

# 数据类型
number = 10
floating_point = 3.14
boolean = True
string = "Hello, World!"
print(number, floating_point, boolean, string)  # 输出 10 3.14 True Hello, World!

字符串操作

# 字符串拼接
first_name = "John"
last_name = "Doe"
full_name = first_name + " " + last_name
print(int(full_name) ) # 输出 John Doe

# 字符串格式化
age = 30
print(f"My name is {first_name} {last_name} and I am {age} years old.")  # 输出 My name is John Doe and I am 30 years old.

列表

# 创建列表
numbers = [1, 2, 3, 4, 5]
print(numbers)  # 输出 [1, 2, 3, 4, 5]

# 列表操作
numbers.append(6)
print(numbers)  # 输出 [1, 2, 3, 4, 5, 6]

元组

# 创建元组
point = (1, 2, 3)
print(point)  # 输出 (1, 2, 3)

字典

# 创建字典
person = {"name": "Alice", "age": 30}
print(person)  # 输出 {'name': 'Alice', 'age': 30}

if条件语句

age = 18
if age >= 18:
    print("You are an adult.")
else:
    print("You are not an adult yet.")  # 输出 You are an adult.

for 循环

# for 循环
for i in range(5):
    print(i)  # 输出 0 1 2 3 4

while 循环

count = 0
while count < 5:
    print(count)
    count += 1  # 输出 0 1 2 3 4

函数定义

# 定义函数


def greet(name):
    print(f"Hello, {name}!")
    greet("Alice")  # 输出 Hello, Alice!

模块导入

# 导入模块


import math

print(math.sqrt(16))  # 输出 4.0

异常处理

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

文件操作

with open("example.txt", "w") as file:
    file.write("Hello, World!")
    with open("example.txt", "r") as file:
        content = file.read()
        print(content)  # 输出 Hello, World!

类和对象

# 类定义
class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def introduce(self):
        print(f"My name is {self.name} and I am {self.age} years old.")
        alice = Person("Alice", 30)
        alice.introduce()  # 输出 My name is Alice and I am 30 years old.

列表推导式

# 快速创建列表

squares = [x ** 2 for x in range(5)]
print(squares)  # 输出 [0, 1, 4, 9, 16]

# 字典推导式快速创建字典
square_dict = {x: x ** 2 for x in range(5)}
print(square_dict)  # 输出 {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

集合

# 创建集合
unique_chars = {char for char in "hello"}
print(unique_chars)  # 输出 {'h', 'e', 'l', 'o'}

排序

# 对列表排序
numbers = [3, 1, 4, 1, 5, 9]
sorted_numbers = sorted(numbers)
print(sorted_numbers)  # 输出 [1, 1, 3, 4, 5, 9]

过滤

# 使用filter()过滤列表
numbers = [1, 2, 3, 4, 5]
evens = list(filter(lambda x: x % 2 == 0, numbers))
print(evens)  # 输出 [2, 4]

映射

numbers = [1, 2, 3]
squared = list(map(lambda x: x ** 2, numbers))
print(squared)  # 输出 [1, 4, 9]

枚举

# enumerate()循环带索引
for i, val in enumerate(['a', 'b', 'c']): print(i, val)  # 输出 0 a 1 b 2 c