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author | Andrew M. Kuchling <amk@amk.ca> | 2006-09-12 21:09:02 (GMT) |
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committer | Andrew M. Kuchling <amk@amk.ca> | 2006-09-12 21:09:02 (GMT) |
commit | 32cec80b0219ff9e0b52baa3580878103af722d3 (patch) | |
tree | 27ee9cbb6b706e0b12d3c5974cf960d44fdfbdad /Doc | |
parent | abd5520cff4404929440d51fff808dee4560584e (diff) | |
download | cpython-32cec80b0219ff9e0b52baa3580878103af722d3.zip cpython-32cec80b0219ff9e0b52baa3580878103af722d3.tar.gz cpython-32cec80b0219ff9e0b52baa3580878103af722d3.tar.bz2 |
Some editing, markup fixes
Diffstat (limited to 'Doc')
-rw-r--r-- | Doc/lib/libsqlite3.tex | 47 |
1 files changed, 24 insertions, 23 deletions
diff --git a/Doc/lib/libsqlite3.tex b/Doc/lib/libsqlite3.tex index 45e67f7..1afb5d7 100644 --- a/Doc/lib/libsqlite3.tex +++ b/Doc/lib/libsqlite3.tex @@ -464,20 +464,19 @@ This is how SQLite types are converted to Python types by default: \lineii{BLOB}{buffer} \end{tableii} -The type system of the \module{sqlite3} module is extensible in both ways: you can store +The type system of the \module{sqlite3} module is extensible in two ways: you can store additional Python types in a SQLite database via object adaptation, and you can let the \module{sqlite3} module convert SQLite types to different Python types via converters. \subsubsection{Using adapters to store additional Python types in SQLite databases} -Like described before, SQLite supports only a limited set of types natively. To +As described before, SQLite supports only a limited set of types natively. To use other Python types with SQLite, you must \strong{adapt} them to one of the sqlite3 -module's supported types for SQLite. So, one of NoneType, int, long, float, +module's supported types for SQLite: one of NoneType, int, long, float, str, unicode, buffer. -The \module{sqlite3} module uses the Python object adaptation, like described in PEP 246 -for this. The protocol to use is \class{PrepareProtocol}. +The \module{sqlite3} module uses Python object adaptation, as described in \pep{246} for this. The protocol to use is \class{PrepareProtocol}. There are two ways to enable the \module{sqlite3} module to adapt a custom Python type to one of the supported ones. @@ -493,8 +492,8 @@ class Point(object): self.x, self.y = x, y \end{verbatim} -Now you want to store the point in a single SQLite column. You'll have to -choose one of the supported types first that you use to represent the point in. +Now you want to store the point in a single SQLite column. First you'll have to +choose one of the supported types first to be used for representing the point. Let's just use str and separate the coordinates using a semicolon. Then you need to give your class a method \code{__conform__(self, protocol)} which must return the converted value. The parameter \var{protocol} will be @@ -507,13 +506,13 @@ return the converted value. The parameter \var{protocol} will be The other possibility is to create a function that converts the type to the string representation and register the function with \method{register_adapter}. - \verbatiminput{sqlite3/adapter_point_2.py} - \begin{notice} The type/class to adapt must be a new-style class, i. e. it must have \class{object} as one of its bases. \end{notice} + \verbatiminput{sqlite3/adapter_point_2.py} + The \module{sqlite3} module has two default adapters for Python's built-in \class{datetime.date} and \class{datetime.datetime} types. Now let's suppose we want to store \class{datetime.datetime} objects not in ISO representation, @@ -523,16 +522,17 @@ but as a \UNIX{} timestamp. \subsubsection{Converting SQLite values to custom Python types} -Now that's all nice and dandy that you can send custom Python types to SQLite. +Writing an adapter lets you send custom Python types to SQLite. But to make it really useful we need to make the Python to SQLite to Python -roundtrip work. +roundtrip work. Enter converters. -Let's go back to the Point class. We stored the x and y coordinates separated -via semicolons as strings in SQLite. +Let's go back to the \class{Point} class. We stored the x and y +coordinates separated via semicolons as strings in SQLite. -Let's first define a converter function that accepts the string as a parameter and constructs a Point object from it. +First, we'll define a converter function that accepts the string as a +parameter and constructs a \class{Point} object from it. \begin{notice} Converter functions \strong{always} get called with a string, no matter @@ -558,11 +558,12 @@ database is actually a point. There are two ways of doing this: \item Explicitly via the column name \end{itemize} -Both ways are described at \ref{sqlite3-Module-Contents} in the text explaining -the constants \constant{PARSE_DECLTYPES} and \constant{PARSE_COlNAMES}. +Both ways are described in section~\ref{sqlite3-Module-Contents}, in +the text explaining the constants \constant{PARSE_DECLTYPES} and +\constant{PARSE_COLNAMES}. -The following example illustrates both ways. +The following example illustrates both approaches. \verbatiminput{sqlite3/converter_point.py} @@ -571,8 +572,8 @@ The following example illustrates both ways. There are default adapters for the date and datetime types in the datetime module. They will be sent as ISO dates/ISO timestamps to SQLite. -The default converters are registered under the name "date" for datetime.date -and under the name "timestamp" for datetime.datetime. +The default converters are registered under the name "date" for \class{datetime.date} +and under the name "timestamp" for \class{datetime.datetime}. This way, you can use date/timestamps from Python without any additional fiddling in most cases. The format of the adapters is also compatible with the @@ -584,12 +585,12 @@ The following example demonstrates this. \subsection{Controlling Transactions \label{sqlite3-Controlling-Transactions}} -By default, the \module{sqlite3} module opens transactions implicitly before a DML -statement (INSERT/UPDATE/DELETE/REPLACE), and commits transactions implicitly -before a non-DML, non-DQL statement (i. e. anything other than +By default, the \module{sqlite3} module opens transactions implicitly before a Data Modification Language (DML) +statement (i.e. INSERT/UPDATE/DELETE/REPLACE), and commits transactions implicitly +before a non-DML, non-query statement (i. e. anything other than SELECT/INSERT/UPDATE/DELETE/REPLACE). -So if you are within a transaction, and issue a command like \code{CREATE TABLE +So if you are within a transaction and issue a command like \code{CREATE TABLE ...}, \code{VACUUM}, \code{PRAGMA}, the \module{sqlite3} module will commit implicitly before executing that command. There are two reasons for doing that. The first is that some of these commands don't work within transactions. The other reason |