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Question

This code

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

equivalent to this

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

or next?

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

This article: http://effbot.org/zone/python-with-statement.htm suggests (if I understand it correctly) that the latter is true. However, the first would make sense to me. If I am wrong, what am I missing?

Answer 1

It is equivalent to the latter, because until open()it returns, it fdoes not matter and should not be closed.

Answer 2

According to the documentation :

The syntax proposes a new statement:

with EXPR as VAR:
    BLOCK

Translation of the above statement:

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)

. try ... finaly.