diff --git a/Doc/faq/design.rst b/Doc/faq/design.rst index 962b4ef4fc8..25c72db89b7 100644 --- a/Doc/faq/design.rst +++ b/Doc/faq/design.rst @@ -297,8 +297,9 @@ use the ``join()`` function from the string module, which allows you to write :: How fast are exceptions? ------------------------ -A try/except block is extremely efficient. Actually catching an exception is -expensive. In versions of Python prior to 2.0 it was common to use this idiom:: +A try/except block is extremely efficient if no exceptions are raised. Actually +catching an exception is expensive. In versions of Python prior to 2.0 it was +common to use this idiom:: try: value = mydict[key] @@ -309,11 +310,10 @@ expensive. In versions of Python prior to 2.0 it was common to use this idiom:: This only made sense when you expected the dict to have the key almost all the time. If that wasn't the case, you coded it like this:: - if mydict.has_key(key): + if key in mydict: value = mydict[key] else: - mydict[key] = getvalue(key) - value = mydict[key] + value = mydict[key] = getvalue(key) .. note::