[Python-es] Wrapper MySQL

[Juan José Rojo]

Buscando por ahí, he encontrado este wapper para sql, os dejo el código del archivo y el link del artículo, a ver si los entendidos nos podéis desmenuzar el código, yo hay cosas como el __delitem__ y alguna otra que no he conseguido hacer funcionar, también alguna idea para mejorarlo como añadir "inner join", falta también un controlador de campos par insertar o actualizar registros de un campo en concreto, sin más y gracias por su atención.

http://www.devx.com/dbzone/Article/22093/1954?pf=true

#!/usr/bin/python

# Modify the following to support other databases:
import MySQLdb
dbmod = MySQLdb
get_tables = "show tables;"  # how to get a list of tables
row_id = "_rowid"  # name of the row ID keyword

import types

class table:
	"""Emulates a list of DB rows, where each row is a tuple.
		May also be accessed via a string, to pull entire columns.
		Examples:
			t = table(db, "users")
			### select and organize data
			t.search("id< 0:  # add support for negative (from the end) indexing
				item = len(self) + item
				if item < 0:
					raise IndexError, "index too negative"
			q = q + " limit %s, 1" % (item)
			self._query(q)
			return self.dbc.fetchone()
		else:
			raise IndexError, "unsupported index type"

	def __setitem__(self, key, value):
		"Not yet implemented."
		if isinstance(key, types.IntType):
			pass
		else:
			raise IndexError, "index not a number"

	def __delitem__(self, item):
		# the method described in the article:
		#q = "select %s from %s %s %s limit %s, 1" % ("_rowid", self.name, self._search, self._sort, item)
		#self._query(q)
		#rid = self.dbc.fetchone()[0]
		#q = "delete from %s where %s=%s" % (self.name, "_rowid", rid)
		#self._query(q)
		
		# a simpler method:
		rid = self[item][-1]
		q = "delete from %s where %s=%s" % (self.name, row_id, rid)
		self._query(q)

	def insert(self, *row):
		fmt = ("%s," * len(row))[:-1]
		q = "insert into %s values (%s)" % (self.name, fmt)
		self._query(q, row)

	def __iter__(self):
		self._new_cursor()
		q = "select *%s from %s %s %s" % (self._row_id, self.name, self._search, self._sort)
		self._query(q)
		return self

	def next(self):
		r = self.dbc.fetchone()
		if not r:
			self._new_cursor()
			raise StopIteration
		return r

	def __len__(self):
		self._query("select count(*) from %s %s" % (self.name, self._search))
		r = int(self.dbc.fetchone()[0])
		return r

class db:
	"""
	A basic wrapper for databases.  Usage is as follows:
		d = db(user="user", passwd="password", db="database")
		table_name = d.tables()[0]
		t = d.table(table_name)
	The parameters for connect() and __init__() are keyword arguments, given
	directly to your database module.

	If you access the same table from several places in your code, there is no
	need to pass the table object around.  This class will keep track of them
	for you and provide the existing copy of a table, if one already exists.
	"""
	def __init__(self, **args):
		self._tables = {}
		if args:
			self.connect(**args)

	def tables(self):
		q = get_tables
		c = self.obj.cursor()
		a = c.execute(q)
		ts = []
		for row in c.fetchall():
			#print row
			ts.append(row[0])

		return ts

	def table(self, name):
		try:
			return self._tables[name]
		except:
			self._tables[name] = table(self, name)
			return self._tables[name]

	def connect(self, **args):
		self.obj = dbmod.connect(**args)

if __name__ == "__main__":
	print "this file should not be executed"

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