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Diffstat (limited to 'Doc/reference/compound_stmts.rst')
| -rw-r--r-- | Doc/reference/compound_stmts.rst | 28 |
1 files changed, 18 insertions, 10 deletions
diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst index 5e093cc..52fc283 100644 --- a/Doc/reference/compound_stmts.rst +++ b/Doc/reference/compound_stmts.rst @@ -22,14 +22,14 @@ also syntactically compound statements. single: clause single: suite -Compound statements consist of one or more 'clauses.' A clause consists of a +A compound statement consists of one or more 'clauses.' A clause consists of a header and a 'suite.' The clause headers of a particular compound statement are all at the same indentation level. Each clause header begins with a uniquely identifying keyword and ends with a colon. A suite is a group of statements controlled by a clause. A suite can be one or more semicolon-separated simple statements on the same line as the header, following the header's colon, or it can be one or more indented statements on subsequent lines. Only the latter -form of suite can contain nested compound statements; the following is illegal, +form of a suite can contain nested compound statements; the following is illegal, mostly because it wouldn't be clear to which :keyword:`if` clause a following :keyword:`else` clause would belong:: @@ -156,8 +156,8 @@ The :keyword:`for` statement is used to iterate over the elements of a sequence The expression list is evaluated once; it should yield an iterable object. An iterator is created for the result of the ``expression_list``. The suite is -then executed once for each item provided by the iterator, in the order of -ascending indices. Each item in turn is assigned to the target list using the +then executed once for each item provided by the iterator, in the order returned +by the iterator. Each item in turn is assigned to the target list using the standard rules for assignments (see :ref:`assignment`), and then the suite is executed. When the items are exhausted (which is immediately when the sequence is empty or an iterator raises a :exc:`StopIteration` exception), the suite in @@ -170,17 +170,25 @@ the :keyword:`else` clause, if present, is executed, and the loop terminates. A :keyword:`break` statement executed in the first suite terminates the loop without executing the :keyword:`else` clause's suite. A :keyword:`continue` statement executed in the first suite skips the rest of the suite and continues -with the next item, or with the :keyword:`else` clause if there was no next +with the next item, or with the :keyword:`else` clause if there is no next item. -The suite may assign to the variable(s) in the target list; this does not affect -the next item assigned to it. +The for-loop makes assignments to the variables(s) in the target list. +This overwrites all previous assignments to those variables including +those made in the suite of the for-loop:: + + for i in range(10): + print(i) + i = 5 # this will not affect the for-loop + # be i will be overwritten with the next + # index in the range + .. index:: builtin: range Names in the target list are not deleted when the loop is finished, but if the -sequence is empty, it will not have been assigned to at all by the loop. Hint: +sequence is empty, they will not have been assigned to at all by the loop. Hint: the built-in function :func:`range` returns an iterator of integers suitable to emulate the effect of Pascal's ``for i := a to b do``; e.g., ``list(range(3))`` returns the list ``[0, 1, 2]``. @@ -284,7 +292,7 @@ keeping all locals in that frame alive until the next garbage collection occurs. object: traceback Before an except clause's suite is executed, details about the exception are -stored in the :mod:`sys` module and can be access via :func:`sys.exc_info`. +stored in the :mod:`sys` module and can be accessed via :func:`sys.exc_info`. :func:`sys.exc_info` returns a 3-tuple consisting of the exception class, the exception instance and a traceback object (see section :ref:`types`) identifying the point in the program where the exception occurred. :func:`sys.exc_info` @@ -461,7 +469,7 @@ A function definition defines a user-defined function object (see section decorator: "@" `dotted_name` ["(" [`parameter_list` [","]] ")"] NEWLINE dotted_name: `identifier` ("." `identifier`)* parameter_list: (`defparameter` ",")* - : ( "*" [`parameter`] ("," `defparameter`)* ["," "**" `parameter`] + : | "*" [`parameter`] ("," `defparameter`)* ["," "**" `parameter`] : | "**" `parameter` : | `defparameter` [","] ) parameter: `identifier` [":" `expression`] |