Python跨文件实例化、跨文件调用及导入库示例代码

a.py
b.py

x = 10

def bar():
    print("bar")

class Foo:
    def hello(self):
        print("hello")

foo = Foo()

from a import Foo, bar, x, foo

f = Foo()
bar()
print(x)
foo.hello()

import a

f = a.Foo()
a.bar()
print(a.x)
a.foo.hello()

# config.py
import requests
session = requests.Session()

# main.py
from config import session
response = session.get("https://api.example.com")

# logger.py
import logging
logger = logging.getLogger("app")

# main.py
from logger import logger
logger.info("Application started")

# 解决方案：函数内导入
def get_processor():
    from file_b import DataProcessor  # 延迟导入
    return DataProcessor()

# 解决方案：使用别名
from module_a import Logger as LoggerA
from module_b import Logger as LoggerB

# 解决方案：条件导入
try:
    import pandas as pd
    HAS_PANDAS = True
except ImportError:
    HAS_PANDAS = False

def process_data(data):
    if HAS_PANDAS:
        return pd.DataFrame(data)
    else:
        return data  # 降级处理

import module                    # 导入模块
from module import obj          # 导入对象
from module import obj as alias # 导入并重命名
from package.module import obj  # 包中模块导入
from . import module           # 相对导入（包内）
from ..parent import module    # 上级包导入