Python的Import机制的模块与包深入理解

# 导入模块
import math

# 使用模块中的函数
result = math.sqrt(25)
print(result)

import math as m

result = m.sqrt(25)
print(result)

from math import sqrt

result = sqrt(25)
print(result)

from math import *

result = sqrt(25)
print(result)

# module_example.py
local_variable = 10

def print_local_variable():
    print(local_variable)

# main.py
import module_example

print(module_example.local_variable)  # 正确
module_example.print_local_variable()  # 正确
print(local_variable)  # 错误，局部变量无法直接访问

# package/__init__.py
from .module import some_function

# package/module.py
def some_function():
    print("Some function in module")

my_package/
|-- __init__.py
|-- module1.py
|-- module2.py
|-- subpackage/
    |-- __init__.py
    |-- module3.py

# 导入整个包
import my_package

# 导入包中的模块或对象
from my_package import module1
from my_package.module2 import some_function

# my_package/__init__.py
print("Initializing my_package")

# my_package/module1.py
def some_function():
    print("Some function in module1")

module_name = "math"  # 可以根据条件选择不同的模块

import importlib
my_module = importlib.import_module(module_name)

result = my_module.sqrt(25)
print(result)

# module_with_execution.py
print("This code will be executed during import")

def some_function():
    print("Some function in module")