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author | Andrew M. Kuchling <amk@amk.ca> | 2003-01-09 13:46:30 (GMT) |
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committer | Andrew M. Kuchling <amk@amk.ca> | 2003-01-09 13:46:30 (GMT) |
commit | 9b44571caae9771fb1f6261aaacc4c001701774a (patch) | |
tree | 5b8665804422573446aa90a6948df43deab3511e /Doc | |
parent | 0f0e6b9d48e2740026fa208e4cdc199d236b3052 (diff) | |
download | cpython-9b44571caae9771fb1f6261aaacc4c001701774a.zip cpython-9b44571caae9771fb1f6261aaacc4c001701774a.tar.gz cpython-9b44571caae9771fb1f6261aaacc4c001701774a.tar.bz2 |
Various minor edits
Diffstat (limited to 'Doc')
-rw-r--r-- | Doc/lib/libdatetime.tex | 57 |
1 files changed, 30 insertions, 27 deletions
diff --git a/Doc/lib/libdatetime.tex b/Doc/lib/libdatetime.tex index 9bd3b52..18edc32 100644 --- a/Doc/lib/libdatetime.tex +++ b/Doc/lib/libdatetime.tex @@ -16,7 +16,7 @@ The \module{datetime} module supplies classes for manipulating dates and times in both simple and complex ways. While date and time arithmetic is supported, the focus of the implementation is on -efficient member extraction, for output formatting and manipulation. +efficient member extraction for output formatting and manipulation. There are two kinds of date and time objects: ``naive'' and ``aware''. This distinction refers to whether the object has any notion of time @@ -28,15 +28,17 @@ whether a particular number represents meters, miles, or mass. Naive \class{datetime} objects are easy to understand and to work with, at the cost of ignoring some aspects of reality. -For applications requiring more, \class{datetime} and \class{time} objects -have an optional time zone information member. -These \class{tzinfo} objects capture information about the offset from -UTC time, the time zone name, and whether Daylight Saving Time is in -effect. Note that no concrete \class{tzinfo} classes are supplied by -the \module{datetime} module. Instead, they provide a framework for -incorporating the level of detail an app may require. The rules for -time adjustment across the world are more political than rational, and -there is no standard suitable for every app. +For applications requiring more, \class{datetime} and \class{time} +objects have an optional time zone information member, +\member{tzinfo}, that can contain an instance of a subclass of +the abstract \class{tzinfo} class. These \class{tzinfo} objects +capture information about the offset from UTC time, the time zone +name, and whether Daylight Saving Time is in effect. Note that no +concrete \class{tzinfo} classes are supplied by the \module{datetime} +module. Instead, they provide a framework for incorporating the level +of detail an application may require. The rules for time adjustment across +the world are more political than rational, and there is no standard +suitable for every application. The \module{datetime} module exports the following constants: @@ -73,22 +75,22 @@ The \module{datetime} module exports the following constants: \end{classdesc*} \begin{classdesc*}{datetime} - A combination of a naive date and a time. + A combination of a date and a time. Attributes: \member{year}, \member{month}, \member{day}, \member{hour}, \member{minute}, \member{second}, \member{microsecond}, and \member{tzinfo}. \end{classdesc*} \begin{classdesc*}{timedelta} - A duration, expressing the difference between two \class{date}, - \class{time}, or \class{datetime} instances, to microsecond + A duration expressing the difference between two \class{date}, + \class{time}, or \class{datetime} instances to microsecond resolution. \end{classdesc*} \begin{classdesc*}{tzinfo} An abstract base class for time zone information objects. These are used by the \class{datetime} and \class{time} classes to - provided a customizable notion of time adjustment (for example, to + provide a customizable notion of time adjustment (for example, to account for time zone and/or daylight saving time). \end{classdesc*} @@ -98,7 +100,7 @@ Objects of the \class{date} type are always naive. An object \var{d} of type \class{time} or \class{datetime} may be naive or aware. \var{d} is aware if \code{\var{d}.tzinfo} is not -\code{None}, and \code{\var{d}.tzinfo.utcoffset(\var{d})} does not return +\code{None} and \code{\var{d}.tzinfo.utcoffset(\var{d})} does not return \code{None}. If \code{\var{d}.tzinfo} is \code{None}, or if \code{\var{d}.tzinfo} is not \code{None} but \code{\var{d}.tzinfo.utcoffset(\var{d})} returns \code{None}, \var{d} @@ -132,12 +134,12 @@ between two dates or times. Only \var{days}, \var{seconds} and \var{microseconds} are stored internally. Arguments are converted to those units: -\begin{verbatim} -A millisecond is converted to 1000 microseconds. -A minute is converted to 60 seconds. -An hour is converted to 3600 seconds. -A week is converted to 7 days. -\end{verbatim} +\begin{itemize} + \item A millisecond is converted to 1000 microseconds. + \item A minute is converted to 60 seconds. + \item An hour is converted to 3600 seconds. + \item A week is converted to 7 days. +\end{itemize} and days, seconds and microseconds are then normalized so that the representation is unique, with @@ -148,7 +150,7 @@ A week is converted to 7 days. \item \code{-999999999 <= \var{days} <= 999999999} \end{itemize} - If any argument is a float, and there are fractional microseconds, + If any argument is a float and there are fractional microseconds, the fractional microseconds left over from all arguments are combined and their sum is rounded to the nearest microsecond. If no argument is a float, the conversion and normalization processes @@ -199,6 +201,7 @@ Instance attributes (read-only): Supported operations: +% XXX this table is too wide! \begin{tableiii}{c|l|c}{code}{Operation}{Result}{Notes} \lineiii{\var{t1} = \var{t2} + \var{t3}} {Sum of \var{t2} and \var{t3}. @@ -224,12 +227,11 @@ Supported operations: {(2)} \lineiii{-\var{t1}} {equivalent to \class{timedelta}(-\var{t1.days}, -\var{t1.seconds}, - -\var{t1.microseconds}),and to \var{t1}* -1.} + -\var{t1.microseconds}), and to \var{t1}* -1.} {(1)(4)} \lineiii{abs(\var{t})} {equivalent to +\var{t} when \code{t.days >= 0}, and to - -\var{t} when \code{t.days < 0}. - overflow.} + -\var{t} when \code{t.days < 0}.} {(2)} \end{tableiii} \noindent @@ -257,7 +259,7 @@ Comparisons of \class{timedelta} objects are supported with the \class{timedelta} object representing the smaller duration considered to be the smaller timedelta. -\class{timedelta} objects are hashable (usable as dictionary key), +\class{timedelta} objects are hashable (usable as dictionary keys), support efficient pickling, and in Boolean contexts, a \class{timedelta} object is considered to be true if and only if it isn't equal to \code{timedelta(0)}. @@ -332,7 +334,7 @@ Class attributes: Instance attributes (read-only): \begin{memberdesc}{year} - Between \constant{MINYEAR} and \constant{MAXYEAR} inclusive + Between \constant{MINYEAR} and \constant{MAXYEAR} inclusive. \end{memberdesc} \begin{memberdesc}{month} @@ -346,6 +348,7 @@ Instance attributes (read-only): Supported operations: +% XXX rewrite to be a table \begin{itemize} \item date1 + timedelta -> date2 |