diff options
Diffstat (limited to 'Doc/library/stdtypes.rst')
| -rw-r--r-- | Doc/library/stdtypes.rst | 33 |
1 files changed, 28 insertions, 5 deletions
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst index 554cbc5..92183a4 100644 --- a/Doc/library/stdtypes.rst +++ b/Doc/library/stdtypes.rst @@ -352,6 +352,23 @@ Notes: or "-" for Not a Number (NaN) and positive or negative infinity. +All :class:`numbers.Real` types (:class:`int` and +:class:`float`) also include the following operations: + ++--------------------+--------------------------------+--------+ +| Operation | Result | Notes | ++====================+================================+========+ +| ``trunc(x)`` | *x* truncated to Integral | | ++--------------------+--------------------------------+--------+ +| ``round(x[, n])`` | *x* rounded to n digits, | | +| | rounding half to even. If n is | | +| | omitted, it defaults to 0. | | ++--------------------+--------------------------------+--------+ +| ``math.floor(x)`` | the greatest Integral <= *x* | | ++--------------------+--------------------------------+--------+ +| ``math.ceil(x)`` | the least Integral >= *x* | | ++--------------------+--------------------------------+--------+ + .. XXXJH exceptions: overflow (when? what operations?) zerodivision @@ -366,7 +383,7 @@ Integers support additional operations that make sense only for bit-strings. Negative numbers are treated as their 2's complement value (this assumes a sufficiently large number of bits that no overflow occurs during the operation). -The priorities of the binary bit-wise operations are all lower than the numeric +The priorities of the binary bitwise operations are all lower than the numeric operations and higher than the comparisons; the unary operation ``~`` has the same priority as the other unary numeric operations (``+`` and ``-``). @@ -1319,10 +1336,11 @@ Notes: *cmp* specifies a custom comparison function of two arguments (list items) which should return a negative, zero or positive number depending on whether the first argument is considered smaller than, equal to, or larger than the second - argument: ``cmp=lambda x,y: cmp(x.lower(), y.lower())`` + argument: ``cmp=lambda x,y: cmp(x.lower(), y.lower())``. The default value + is ``None``. *key* specifies a function of one argument that is used to extract a comparison - key from each list element: ``key=str.lower`` + key from each list element: ``key=str.lower``. The default value is ``None``. *reverse* is a boolean value. If set to ``True``, then the list elements are sorted as if each comparison were reversed. @@ -2005,7 +2023,12 @@ Files have the following methods: argument is optional and defaults to ``os.SEEK_SET`` or ``0`` (absolute file positioning); other values are ``os.SEEK_CUR`` or ``1`` (seek relative to the current position) and ``os.SEEK_END`` or ``2`` (seek relative to the file's - end). There is no return value. Note that if the file is opened for appending + end). There is no return value. + + For example, ``f.seek(2, os.SEEK_CUR)`` advances the position by two and + ``f.seek(-3, os.SEEK_END)`` sets the position to the third to last. + + Note that if the file is opened for appending (mode ``'a'`` or ``'a+'``), any :meth:`seek` operations will be undone at the next write. If the file is only opened for writing in append mode (mode ``'a'``), this method is essentially a no-op, but it remains useful for files @@ -2138,7 +2161,7 @@ to be provided for a context manager object to define a runtime context: the context expression in a :keyword:`with` statement. An example of a context manager that returns a related object is the one - returned by ``decimal.Context.get_manager()``. These managers set the active + returned by :func:`decimal.localcontext`. These managers set the active decimal context to a copy of the original decimal context and then return the copy. This allows changes to be made to the current decimal context in the body of the :keyword:`with` statement without affecting code outside the |