Python3：with open() as

读写文件：with open() as

实例：

def get_env():
    with open(f'{CONF_PATH}/env.ini', encoding='utf-8') as file:
        env = file.read()
    return env

读取文件内容的过程：

file = open(f'{CONF_PATH}/env.ini', encoding='utf-8')
print(file.read())
file.close()

读取文件时可能会产生IOError，一旦出错后面的file.close()就不会被调用，所以使用try … finally来保证无论读取文件是否产生错误都会调用file.close()。

try:
    file = open(f'{CONF_PATH}/env.ini', encoding='utf-8')
    print(file.read())
finally:
    if file:
        file.close()

为了解决复杂性，python引入with语句来调用：

with open(f'{CONF_PATH}/env.ini', encoding='utf-8') as file:
    print(file.read())