Python“with”命令

是这个代码吗

with open(myfile) as f:
    data = f.read()
    process(data)

相当于这个

try:
    f = open(myfile)
    data = f.read()
    process(f)
finally:
    f.close()

或者下面的一个？

f = open(myfile)
try:
    data = f.read()
    process(f)
finally:
    f.close()

本文：http://effbot.org/zone/python-with-statement.htm http://effbot.org/zone/python-with-statement.htm表明（如果我理解正确的话）后者是正确的。然而，前者对我来说更有意义。如果我错了，我错过了什么？

根据文档 https://www.python.org/dev/peps/pep-0343/:

提出了一个新的语句，其语法如下：

with EXPR as VAR:
    BLOCK

上述声明的翻译是：

mgr = (EXPR)
exit = type(mgr).__exit__  # Not calling it yet
value = type(mgr).__enter__(mgr)
exc = True
try:
    try:
        VAR = value  # Only if "as VAR" is present
        BLOCK
    except:
        # The exceptional case is handled here
        exc = False
        if not exit(mgr, *sys.exc_info()):
            raise
        # The exception is swallowed if exit() returns true
finally:
    # The normal and non-local-goto cases are handled here
    if exc:
        exit(mgr, None, None, None)

这是你的扩展版本second代码片段。初始化先于try ... finaly block.