我有一些問題,設計出使用psycopg2庫的說明書中所描述here構建SQL動態查詢使用好轉換型工具
我想建立等於該字符串動態查詢一個很好的算法:
SELECT ST_GeomFromText('POLYGON((0.0 0.0,20.0 0.0,20.0 20.0,0.0 20.0,0.0 0.0))');
正如你看到的,我的Polygon對象包含多個點,在一個簡單的CSV文件some.csv讀取其中包含:
0.0;0.0
20.0;0.0
20.0;20.0
0.0;20.0
0.0;0.0
所以我建立動態查詢,在csv行/數據的數量的函數。
這裏我的程序生成的SQL查詢字符串來執行:
import psycopg2
import csv
# list of points
lXy = []
DSN= "dbname='testS' user='postgres' password='postgres' host='localhost'"
conn = psycopg2.connect(DSN)
curs = conn.cursor()
def genPointText(curs,x,y):
generatedPoint = "%s %s" % (x,y)
return generatedPoint
#Lecture fichier csv
polygonFile = open('some.csv', 'rb')
readerCSV = csv.reader(polygonFile,delimiter = ';')
for coordinates in readerCSV:
lXy.append(genPointText(curs,float(coordinates[0]),float(coordinates[1])))
# function of list concatenation by separator
def convert(myList,separator):
return separator.join([str(i) for i in myList])
# construct simple query with psycopg
def genPolygonText(curs,l):
# http://initd.org/psycopg/docs/usage.html#python-types-adaptation
generatedPolygon = "POLYGON((%s))" % convert(l, ",")
return generatedPolygon
def executeWKT(curs,geomObject,srid):
try:
# geometry ST_GeomFromText(text WKT, integer srid);
finalWKT = "SELECT ST_GeomFromText('%s');" % (geomObject)
print finalWKT
curs.execute(finalWKT)
except psycopg2.ProgrammingError,err:
print "ERROR = " , err
polygonQuery = genPolygonText(curs,lXy)
executeWKT(curs,polygonQuery,4326)
正如你所看到的,這是工作,但這種方式是不是因爲Python對象和SQL PostgreSQL的對象之間的轉換問題是正確的。
在文檔中,我只看到了爲靜態查詢提供並轉換數據的示例。你知道一個「優雅」的方式來創建正確的字符串與正確的類型在查詢動態構建?
更新1:
正如你所看到的,當我在這個簡單的例子使用psycopg類型的轉換功能,我有錯誤是這樣的:
query = "ST_GeomFromText('POLYGON((52.146542 19.050557, 52.148430 19.045527, 52.149525 19.045831, 52.147400 19.050780, 52.147400 19.050780, 52.146542 19.050557))',4326)"
name = "my_table"
try:
curs.execute('INSERT INTO %s(name, url, id, point_geom, poly_geom) VALUES (%s);', (name,query))
except psycopg2.ProgrammingError,err:
print "ERROR = " , err
錯誤等於:
ERROR = ERREUR: erreur de syntaxe sur ou près de « E'my_table' »
LINE 1: INSERT INTO E'my_table'(name, poly_geom) VALUES (E'ST_GeomFr...
更新2:
最後的代碼工作,感謝stackoverflow用戶!
#info lib : http://www.initd.org/psycopg/docs/
import psycopg2
# info lib : http://docs.python.org/2/library/csv.html
import csv
# list of points
lXy = []
DSN= "dbname='testS' user='postgres' password='postgres' host='localhost'"
print "Opening connection using dns:", DSN
conn = psycopg2.connect(DSN)
curs = conn.cursor()
def genPointText(curs,x,y):
generatedPoint = "%s %s" % (x,y)
return generatedPoint
#Lecture fichier csv
polygonFile = open('some.csv', 'rb')
readerCSV = csv.reader(polygonFile,delimiter = ';')
for coordinates in readerCSV:
lXy.append(genPointText(curs,float(coordinates[0]),float(coordinates[1])))
# function of list concatenation by separator
def convert(myList,separator):
return separator.join([str(i) for i in myList])
# construct simple query with psycopg
def genPolygonText(l):
# http://initd.org/psycopg/docs/usage.html#python-types-adaptation
generatedPolygon = "POLYGON((%s))" % convert(l, ",")
return generatedPolygon
def generateInsert(curs,tableName,name,geomObject):
curs.execute('INSERT INTO binome1(name,geom) VALUES (%s, %s);' , (name,geomObject))
def create_db_binome(conn,name):
curs = conn.cursor()
SQL = (
"CREATE TABLE %s"
" ("
" polyname character varying(15),"
" geom geometry,"
" id serial NOT NULL,"
" CONSTRAINT id_key PRIMARY KEY (id)"
")"
" WITH ("
" OIDS=FALSE"
");"
" ALTER TABLE %s OWNER TO postgres;"
) %(name,name)
try:
#print SQL
curs.execute(SQL)
except psycopg2.ProgrammingError,err:
conn.rollback()
dropQuery = "ALTER TABLE %s DROP CONSTRAINT id_key; DROP TABLE %s;" % (name,name)
curs.execute(dropQuery)
curs.execute(SQL)
conn.commit()
def insert_geometry(polyname,tablename,geometry):
escaped_name = tablename.replace('""','""')
try:
test = 'INSERT INTO %s(polyname, geom) VALUES(%%s, ST_GeomFromText(%%s,%%s))' % (escaped_name)
curs.execute(test, (tablename, geometry, 4326))
conn.commit()
except psycopg2.ProgrammingError,err:
print "ERROR = " , err
################
# PROGRAM MAIN #
################
polygonQuery = genPolygonText(lXy)
srid = 4326
table = "binome1"
create_db_binome(conn,table)
insert_geometry("Berlin",table,polygonQuery)
insert_geometry("Paris",table,polygonQuery)
polygonFile.close()
conn.close()
什麼是從你的程序生成的查詢文本?什麼是錯誤信息? –
我更新了簡單的例子和錯誤跟蹤:) – reyman64